Service Provider Bridging Concepts

0:05Let's kick this playlist off with something big right out

0:08of the gate, something that's really relevant to service

0:10provider networks, and that is provider bridging.

0:13What really is provider bridging at the end of the day?

0:16Well, that's really what this entire skill is all about.

0:19We're going to be exploring how service providers can actually

0:22extend Layer 2 connectivity from one customer site all

0:26the way across their provider backbone

0:28into another customer site.

0:30We're even going to talk about what

0:31happens when more than one service provider comes

0:33into the mix.

0:34But here's the real kicker.

0:35I really wanted to start out with this topic right now,

0:37the service provider bridging, because lots of people

0:40feel like this is one of the hardest things

0:42to wrap their head around.

0:43So we need to tackle the big hard, thing first and get

0:46a major win under our belt as we progress through the service

0:49provider journey.

0:50So by the end of this skill, we'll

0:51fully understand what service provider bridging really

0:55does for us at the end of the day.

0:56What did the 802.1ad standard bring to the table?

1:00And how does a frame at a customer site

1:02make its way across a service provider's network all the way

1:06to the customer's other site?

1:07That's what this skill is going to uncover for us.

1:10So let's get going.

0:05Now here's a little story.

0:06When I first made my way into the service provider world,

0:09I actually started exploring service provider technologies

0:12thanks to Juniper and Juniper Certification Track.

0:15But coming from the Enterprise world,

0:17the service provider world really caught me off guard.

0:20And there were some of the topics

0:22that I found really, really blown away about how deep

0:25and how much planning and how much design actually

0:27goes into manipulating all of these protocols.

0:29And the one thing that really caught

0:31me off guard the most that I found most challenging to wrap

0:33my head around was actually service provider bridging.

0:36You ready for the big spoiler at the end of the day, one

0:38of the things that you need to keep in mind as you journey

0:40through service provider bridging

0:41and that will really help you get through this?

0:43It's just dot 1Q trunking at the end of the day.

0:46So in this skill, what we're going to do

0:47is we're going to take a look at what the dot 1Q protocol really

0:50brought to the table and where some of the limitations where

0:53challenges came in for a service provider's network

0:56when they wanted to extend layer 2 services to their customers.

0:59So let's recap what dot 1Q really

1:01does, how it processes a frame and tags

1:03traffic as it goes over a trunk port,

1:05and then take a look at what a service provider may

1:07think about this type of traffic as it arrives on their devices.

1:10Let's get going.

1:11So I guess we need to launch right into this

1:13and settle the score right now.

1:15What is it that provider bridging really

1:17does at the end of the day?

1:18Take a look at this topology that I'm

1:20going to be using for the upcoming Nuggets,

1:22at least in this skill and the next skill.

1:24What we're really talking about in the blue section right

1:27here is going to be a customer network.

1:30And this pink section here is going

1:32to be their actual service provider network.

1:34Now in this blue section, we have their first site, which

1:37is obviously located in a city.

1:39Now over here, we also have the exact same customer.

1:42And they have a different site.

1:44Maybe that site is located in a different city,

1:47or different state, or maybe even in a different country.

1:49Whatever the case is, in order to get traffic moving

1:53from Site A to Site B, a service provider

1:56has to help them get there.

1:58So the point of a bridge is to actually extend a layer 2

2:03network from one end to the other.

2:06If you kind of look at it, what does this topology actually

2:09remind you of?

2:10It kind of reminds me of a bridge.

2:12We're going from one bit of land on one side of the water

2:15to another bit of land on a different side of the water.

2:18And the bridge is what actually gets us there.

2:21So yeah, do you see it?

2:22Does it make sense that at this point, what a bridge is really

2:24going to do is it's just going to give us across a service

2:27provider network.

2:28But really more specifically, what a service provider bridge

2:31is doing is it is providing layer 2 connectivity from one

2:35end to the other.

2:36And now is the part where you go think, how do they do that?

2:39Is it just a trunk port?

2:40And that really sets up the conversation about what it is

2:43that 802.1Q does and where it kind of falls short.

2:47You see, when we try to do 902.1Q trunking from one site

2:52to the next site, we found out pretty quickly that there are

2:55limitations, at least from the service provider's point

2:57of view, to actually providing just a simple layer 2 broadcast

3:02VLAN that they could send their tag traffic

3:04into, into the service provider network.

3:06Sure, we could absolutely create a trunk port,

3:09like a classic 802.1Q trunk port between this link right here.

3:14And that way traffic that originates from, say,

3:16this host here could be trunked up.

3:18And then we could just trunk it down here,

3:20then trunk it over here, then trunk it over here.

3:22And now it makes its way out.

3:24And this would behave as if our entire service provider network

3:26is nothing but switching.

3:28That is technically a solution that could fly.

3:31But we find out there are so many variables and so many

3:34problems with 802.1Q when we start talking about this.

3:37Let's talk about one of the first major issues with 802.1Q.

3:41And that's the actual tag itself.

3:43It's hard to beat Wikipedia for getting some good information

3:45about ethernet frames.

3:46And when I was in a pinch and needed,

3:48I need somebody to send me the header of a frame real quick,

3:50let's just use Wikipedia as our source to get that done.

3:53What I'm focused on right now is this piece of an Ethernet frame

3:57right here, the 802.1Q tag.

4:00Now we see that it is comprised of four octets,

4:03or it is 32 bits.

4:05And when you think about 32 bits, how many addresses

4:08is that total?

4:09That actually means there's something

4:11like 4 billion addresses that you could actually

4:13use at that point.

4:14But if we've ever worked with VLANs

4:15before, we know, wait a minute, I've

4:17never seen a VLAN 195,000 before.

4:21No, that's because the actual 802.1Q tag and the VLAN numbers

4:25that we're allowed to do-- if I give it a click here,

4:27we can scroll into it-- we can see that the actual 802.1Q

4:31header itself, right there, has these four octets defined by 1,

4:362, 3, 4.

4:37But the real kicker is the first octets

4:39are reserved by the tag protocol identifier.

4:43And then we see actually down here in the tag format,

4:46that the next four bits are also reserved,

4:49leaving only 12 bits that are usable for actually setting

4:53a VLAN ID.

4:54From the service provider's point of view,

4:56this means that we can only come up with 12 bits of VLAN

5:00information for all of our customers if we were to use

5:04802.1Q trunking.

5:06So jumping back to this diagram here,

5:08what we're saying is that this customer right here,

5:12if it wanted to use 802.1Q trunking,

5:15we could assign anything within those 12 bits and tell that

5:18customer, go ahead and trunk up to us with your data tagged

5:22with a specific VLAN.

5:23So let's pretend for a moment the customer said,

5:25that's great and all, but I actually

5:27want to send three or four VLANs across this trunk port for you.

5:31And you're like, OK, go ahead and send for VLANs.

5:34The real kicker is with these 12 bits,

5:36that means we only have 4,094 usable VLAN

5:41tags that we can use.

5:42And four of those just went to one customer.

5:45Do you already see where I'm going with this?

5:47One of the biggest issues with 801.1Q is that it

5:50isn't scalable.

5:51If we are a large service provider network-- maybe

5:54we're like a huge one like AT&T, or Vodafone, or Orange,

5:58or whatever.

5:58Maybe we're a massive service provider network.

6:01If we're only allowed 4,094 VLAN tags,

6:05obviously we're going to need some

6:06of those VLANs for our own internal network

6:09and our own trunking and VLANs that we're doing.

6:11But then all of a sudden, we are limited to the amount of VLANs

6:15that we can actually use for our customers.

6:17If we have thousands of customers,

6:19for instance, if we have more than 4,094 customers,

6:22we've just run out of VLANs, even

6:24if we gave them one VLAN each.

6:27So that's a major, major problem with 802.1Q trunking,

6:30is it even though the VLAN tag itself is a 32-bit field,

6:34only 12 of those bits make up the actual VLAN number itself.

6:38And therefore, there are only 4,094 VLANs

6:42within an actual VLAN environment.

6:44And as a service provider, if we have thousands

6:47upon thousands of customers, we simply run out of VLAN tags.

6:50And therefore, that's not going to cut it for us.

6:52But let's pretend for a moment that we

6:54didn't run out of VLAN tags.

6:55And we did sell this customer its four VLANs.

6:58What is the next issue that we're going to run into, is all

7:01of a sudden, this one VLAN-- let's pretend it's VLAN 110--

7:05this one VLAN 110 spans to here, then here, then here, then

7:09here.

7:10And what do you know about trunk ports, and routing loops,

7:13and switch loops, and frame loops?

7:15Spanning tree protocol.

7:18All of a sudden, now we have a spanning tree protocol issue,

7:22because our spanning tree protocol for this one VLAN

7:25has to span from the customer's network

7:28across our entire provider backbone, all the way

7:31into the other customer's network.

7:33Now you're thinking here, that's only five switches.

7:35What's the big deal, Knox?

7:37But in a real service provider network,

7:39how many jumps or hops or physical devices

7:42is this frame actually going to pass through?

7:44Potentially a lot.

7:45And now all of a sudden, this spanning tree environment

7:48has to span the entire duration, the entire length

7:51of this entire topology.

7:53And that becomes another major problem,

7:55because not only do we have to have

7:56spanning tree protocol able to converge

7:59and be deployed and scalable in that nature,

8:01we also have to just coordinate that many instances of spanning

8:05tree protocol against all of the different VLANs

8:08and then keep in mind like, who's going to be root bridge?

8:10And what was this customer doing again?

8:12What kind of hardware were they using?

8:14Because they might be using Cisco, and we're using Juniper,

8:16and we use different versions of spanning tree protocol.

8:19So that becomes an administrative nightmare too.

8:22Now one of the last problems with 802.1Q is think about

8:25the very processing of how a frame goes.

8:28If this device sends a ping destined to this device,

8:32and they believe they're on the same subnet,

8:34because our layer 2 topology spans that far,

8:38what does it really begin with?

8:40It begins with an ARP request, doesn't it?

8:42So that frame is going to enter right here on our provider

8:46equipment.

8:46And unless we've already learned about this Mac address

8:492, what is the default behavior on just VLAN switching

8:53or ethernet switching?

8:54If we don't know the outbound interface to send this on,

8:57it's going to broadcast the frame out all interfaces that

9:03are participating in the same VLAN,

9:04except, of course, the interface that the packet was received on

9:08or the frame was received on.

9:09So the frame will come in on this interface.

9:11And it'll get broadcast out all the other interfaces here.

9:14And then it'll come in on this interface.

9:16And it'll get broadcast out all the interfaces here.

9:19And then it'll come in on this interface.

9:20And it'll make its way out.

9:22Then return traffic has to make its way back in.

9:24And the broadcasts aren't necessarily the big deal.

9:27The big thing we're setting up here is our environment now has

9:31to learn about all of our customer's Mac addresses,

9:35because if we're going to be using an 802.1Q VLAN,

9:38all of the rules of ethernet switching apply here.

9:41So now in our entire provider environment,

9:45again, thinking about the fact that there

9:46could be 4,094 VLANs for all of our customers,

9:50now we have to learn all of our customer's Mac addresses.

9:54That's right.

9:55So these are some big limitations to actually using

9:58902.1Q, the fact that we only have 4,094 VLANs that we can

10:02play with and divvy up among our customers,

10:04the fact that spanning tree protocol is going to be in play

10:08here, and we're going to have to coordinate the deployment

10:10of spanning tree protocol for the entire VLAN,

10:13because that's going to span from one customer site all

10:16the way through a backbone into the other customer site.

10:18And then lastly, we're going to have

10:20to learn all of our customer's Mac addresses

10:23to send traffic from one site to the next site.

10:25So that sets up kind of the problems with 802.1Q.

10:28Let's talk about how service providers overcame this

10:31in such a fascinatingly simple way in the next Nugget.

10:34I hope this has been informative for you.

10:36And I'd like to thank you for viewing.

0:00[MUSIC PLAYING]

0:05For all of the awesome things that 802.1Q did

0:08for the enterprise world, allowing us to segment

0:10broadcast domains into multiple VLANs and then still be able

0:14to carry those VLANs across a trunk port by tagging it,

0:17we found out that there is a scale problem when it comes

0:20to service provider networks.

0:21They weren't able to extend layer 2 technologies all

0:24the way from one customer site to another customer site

0:27unless we had a very small number of customers actually

0:30demanding this.

0:31The issue is that that VLAN tag field is only a 12-bit field

0:35and therefore, only has 4,094 usable VLAN

0:38tags that we could actually use to help with our customers.

0:41Beyond that, we would have to coordinate things, like, MAC

0:44address table usage, as well as Spanning Tree Protocol

0:46usage across an entire infrastructure

0:49between both customers and with the service provider backbone

0:52itself.

0:53So enter 802.1ad, or what's also known as Q-in-Q technology.

0:58We're going to be talking about how 802.1ad addressed almost

1:02all of these issues, not quite all of them,

1:04but most of these issues, and is now one of the preferred ways

1:07that a service provider network can offer an EVC or an ethernet

1:11virtual connection from one customer site to another

1:14customer site.

1:15Let's get going, talking about 802.1ad.

1:18So are you ready to have your mind blown to see how service

1:22providers were able to overcome this limitation of 802.1Q?

1:25Think about this previous example that we set up here.

1:28We had our customer at this site sending in a frame.

1:31And we wanted it to make its way over to this site

1:33as if they were on the exact same layer 2 Ethernet segment.

1:36Let's pretend for a moment that this customer wanted

1:39to use the VLAN of 110.

1:43So it sends a tagged frame into our provider network,

1:47tagged with a VLAN of 110.

1:50What, then, do we do with this to make this so scalable and so

1:53simple that it actually works?

1:55We just add our own tag to it on the outside of that tag.

2:00We'll say we give this customer a tag ID of VLAN 200.

2:04That's right.

2:04That's exactly what's going to happen.

2:06And that's what the 802.1ad standard did is it created what

2:12is called Q-in-Q tunneling.

2:15That's right because it's 802.1Q tags inside of 802.1Q tags.

2:20Now, this concept may feel a little fuzzy right now.

2:23So don't worry.

2:24What we're going to do in this Nugget is now talk about how

2:27does 802.1ad really work.

2:30So in this scenario, what we as the service provider are saying

2:33is that our customer comes to us and they

2:35say they want layer 2 connectivity

2:38from this site here all the way to this site here.

2:42But they also don't want to be limited in the number of VLANs

2:46that they can actually use.

2:47So what they want to do is they really want

2:49to have the world open to them.

2:51They want to be able to use VLAN 1 through VLAN 4,094.

2:55So if we have an 802.1Q trunk right here between this link,

3:00between their customer equipment and our service provider

3:04equipment, we know that they're going to be tagging traffic

3:07as it goes up here.

3:08And it could be tagged with a VLAN

3:11of anywhere between one and 94.

3:13Let's go ahead and be really clever and call this tag

3:16the customer tag or C tag for short.

3:21And let's pretend for a moment that this device right here

3:24lives on VLAN 110.

3:26So it's going to be sending traffic in to this device

3:29and it gets tagged as it goes up to our equipment

3:31with a C tag of 110.

3:33We as a service provider do not want

3:36to have to worry about how many VLANs they want to use,

3:39nor do we want to worry about coordinating a Spanning Tree

3:42Protocol instance between them.

3:44So what we decide to do is we decide

3:46to assign this entire customer their own VLAN tag.

3:50Pretend for a moment that we say that this customer has

3:53a VLAN tag of 200.

3:55So in the Ethernet frame itself, they

3:58have sent us a frame that has a C tag of 110.

4:01And we're going to put a little tag on the outside of it.

4:05This is called the service tag or S tag for short

4:09And we're going to label it with an S tag of 200.

4:12So as the frame arrives on this device,

4:14we add the S tag of 200.

4:17And then forward it via a trunk port down to our next device.

4:22This device that sits dead center of it receives the frame

4:26and only looks at the S tag.

4:28It doesn't care about the C tag.

4:30It's only looking at the S tag.

4:31And it knows, oh, for S tag traffic, that's VLAN 200.

4:35And here are the ports that I can send VLAN 200 out of.

4:39So it sends VLAN 200 out some additional ports.

4:42And again, these devices receive the frame

4:46and see that it has an S tag of 200.

4:49But because it's also configured to know what customers it

4:52attaches to, these devices see that they are the end

4:56of the road for VLAN 200.

4:59And it removes the S tag, leaving only the customer tag.

5:03And it forwards the tagged traffic back down

5:06to this customer.

5:07So now think about it as if there were multiple hosts

5:10living off of this device.

5:12And maybe they were sending frames

5:13in on VLAN ID 113 or 493.

5:19They would all be tagged with a C tag.

5:21And then we would just drop our one S tag on the front of it.

5:25Traffic would then be forwarded via the S tag

5:27until it makes its way to the final destination, where the S

5:30tag is removed and then this device, the other customer

5:33device, inspects the C tag and sends the traffic on

5:36towards its next destination.

5:38We can see why this is called Q-in-Q tunneling, can't we?

5:43Because we have an 802.1Q tag inside of an 802.1Q tag.

5:47And pulling up trusty Wikipedia one more time,

5:50we could actually scroll down and take a closer look

5:52at the frame format here.

5:54This last frame format is the one

5:56we care about because here we've got a regular Ethernet frame.

6:00Here we've got one with an 802.1Q header.

6:02And here is an 802.1ad header.

6:05We simply have the two .1Q headers.

6:08Now, the first header that pops up here, this is the S tag.

6:12This is known as the outer tag.

6:15And this tag right here is the C tag.

6:18This is known as the inner tag.

6:21Yes, these are key terms that you should commit to memory.

6:24These are the terms that you would read in a textbook

6:26or maybe even see in an exam environment.

6:28You may see these pop up as the term S tag or C tag

6:32or you may also see them as an outer tag or an inner tag.

6:36So now, on one logical switch, what

6:39I'm saying here, that's a key term, is a logical switch,

6:42I could have 4,094 customers.

6:46And we could carry out of those customers

6:49their 4,094 VLANs because I can have 4,094 S tags.

6:56And we don't care about the inner tag or C tag that's

6:59being trafficked there.

7:00Now, to be fair, you can actually

7:02configure it to care about the C tag.

7:05We can restrict which VLANs are actually allowed

7:07to traverse through a network.

7:09And that's a bigger topic that we're

7:10going to talk about as we progress through this content.

7:13But to mark it even further, if you followed along

7:16in the JNCIA-Junos content, you learned

7:18about routing instances.

7:20And that was the ability to create separate logical routing

7:24instances or virtual instances on each one of our routers.

7:27This was like a VRF, where we could

7:29separate many different routing tables

7:31and logically separate them together.

7:33Here's the real truth.

7:34On these vMX devices or many other switching platforms,

7:38we can actually perform virtual switching.

7:41So we can have separate VLAN databases

7:43and separate MAC address tables.

7:45And therefore, there's really no limit to the amount of VLANs

7:49that we could actually configure and scale

7:51throughout our entire enterprise, except, of course,

7:54within the limitations of the physical hardware itself.

7:56We only have so much processing and RAM and disk space

7:59at the end of the day.

8:00So this introduces what 802.1ad, also known as Q-in-Q,

8:06also known as provider backbone bridging--

8:10it's going to take me forever to write backbone here-- bridging,

8:13there we go.

8:14That's right.

8:14This does kind of have three names at the end of the day.

8:17That introduces what this technology does and how we

8:20actually turned 802.1Q into a scalable protocol that helps us

8:25move layer 2 traffic from one customer site to the other.

8:28At the end of the day, before you go on any further and you

8:31get overwhelmed with this, just remember what we're really

8:34talking about is nothing more than .1Q trunking.

8:37That's really what we're doing.

8:38We've just added one more .1Q tag onto the actual frame

8:42itself.

8:43So that introduces how service provider bridging actually

8:45works.

8:46I hope this has been informative for you.

8:48And I'd like to thank you for viewing.

0:00[MUSIC PLAYING]

0:05So it makes sense why it's called QinQ now, right?

0:08We've got an inner Q tag, and 802.1Q tag,

0:11followed by an outer 802.1Q tag.

0:14And we know that the provider network is only going to be

0:17focused on forwarding the outer 802.1Q tag.

0:20So what we're going to do now is actually

0:22perform a frame walk, where we follow how a frame would enter

0:26the provider network and how it would be processed

0:28and forwarded one hop at a time until it

0:30reaches its final destination.

0:32So let's take a look at the path a frame would walk as it enters

0:35a provider network using 802.1ad QinQ.

0:39So we talked about this a little bit in the previous Nugget.

0:41But it bears some dedicated time in its own right.

0:44It also bears repeating because this

0:46is going to really help you solidify

0:48your understanding of how provider

0:50bridging in QinQ really works.

0:52So let's talk about how a frame would

0:54move from one end of a topology to another when we've

0:57implemented QinQ tagging, especially when

1:00we have more than one customer.

1:01So I've changed the topology up just a little bit

1:04so that we can actually see what a frame

1:06walk would look like if we had multiple customers.

1:08Let's pretend for a moment that we had our blue customer.

1:11I'm going to call it customer A. And we've

1:14decided that we want customer A to have an S tag of 300.

1:19Now we've got our green customer who's also in the mix, too.

1:22Let's say that we've got customer B

1:25and we want them to have an S tag of 400.

1:30Again, keep in mind, it's important to remember

1:32what the difference between C tags and S tags really are.

1:34The C tag is going to be the customer's tag,

1:37meaning what VLAN 802.1Q tag have they applied

1:41to the Ethernet frame versus the S tag,

1:43which is what is the frame that we actually care about?

1:46We are applying it and forwarding it

1:48through our traffic, through our network.

1:49Starting with customer 1, a frame

1:52is originated in customer 1's network over here in this site.

1:56Let's call this site 1.

1:58And it gets tagged with a C tag of 110.

2:03And it arrives inbound on our network on this

2:05switch's ge-0/0/0 interface.

2:08The customers configure their outgoing interface as an 802.1Q

2:12trunk port so that it is tagged as it arrives on our interface.

2:16Now, do we really care about what

2:17it's tagged with at this point?

2:19Absolutely not.

2:20We don't look.

2:21Our device doesn't inspect that tag at all.

2:24It looks at this interface right here and says,

2:26oh, I see this is coming in on my customer A interface.

2:30And I know that customer A really belongs to VLAN 300.

2:35So after we've configured this device to associate ge-0/0/0

2:40here with customer A, customer A can trunk whatever they want

2:44to up to us at this point.

2:45But we know that this interface is really configured

2:48to operate in VLAN 300.

2:50So this device adds the S tag of 300 onto the frame,

2:56even though there is a C tag currently existing of 110.

2:59From there, we have trunk ports going out all of our interfaces

3:03into the provider core.

3:04Our device tags the traffic with the S tag

3:07and forwards it into the provider core.

3:09And the provider core only looks at the S tag.

3:12It only looks at the outermost tag.

3:15It may know that there is a C tag in operation

3:17because the actual tag field itself,

3:20the TPID indicates that it is an 802.1ad frame instead

3:24of an 802.1Q frame.

3:26But nonetheless, our device knows

3:28to inspect the S tag itself and says,

3:30oh, this is part of VLAN 300.

3:33Let me just forward it out all of the other interfaces that

3:35are speaking on VLAN 300, or out the destination

3:39interface if I know about the destination MAC address.

3:42So in this case, the device could send it out

3:45towards this provider device or this provider device

3:48because there are redundant uplinks

3:50into this network on the other customer's remote site.

3:52So the frame gets forwarded via the S tag information of 300

3:57that we have set on the frame as it entered our provider

4:00network.

4:00And as it begins to exit the provider network,

4:03this device knows when it has a leg in the customer's network

4:08as well.

4:08It knows to strip the S tag off of the frame and forward

4:11the original 802.1Q tagged frame towards the host device.

4:16Now, here's the real kicker.

4:17What happens when my other customer, my green customer

4:20down here where R33 is, wants to send

4:23in a frame with a C tag of 110?

4:27It configures and 802.1Q trunk on this interface.

4:31And it sends in the tagged frame with the C tag of 110.

4:35And it receives on ge-0/0/3.

4:38Again, I can't stress this enough.

4:40This device isn't going to inspect the C tag.

4:42But rather it's going to look at how this interface is

4:45configured. ge-0/0/3 would be configured to know, oh, OK,

4:49I belong to customer B's network.

4:52And we're going to apply the S tag of 400 on this frame.

4:56So it applies the S tag of 400 to the frame

4:59and then forwards it out the exact same trunk

5:02port towards the provider core.

5:03The provider core is going to inspect that S tag of 400.

5:07And it sees, ah, I need to send this out of my interfaces

5:10that are also participating in VLAN 400.

5:13Unless, of course, it knows, again, the exact destination

5:16MAC address and the interface it should forward

5:18traffic out of that way.

5:19The whole time this is going on, all of these devices

5:22are also learning about the source MAC addresses

5:25and logging them in their MAC address table.

5:27That's right.

5:28802.1Q solved a bunch of problems,

5:30but didn't solve every problem.

5:32The one problem that it didn't really solve

5:34is we still have to learn our customers MAC addresses.

5:37But we as service providers tend to overcome this problem by,

5:41well, billing them for that.

5:42We could charge them for a maximum number

5:45of MAC addresses.

5:46And if they go over it, we could charge them

5:47an additional amount.

5:49This is why you oftentimes see enterprises create

5:52their own dedicated VLAN specifically

5:54for traversing this backbone.

5:56And then they actually perform some form of NAT

5:59before the traffic goes outbound into this provider backbone.

6:02Nonetheless, this is a way that we can still

6:04maintain our resources at a reasonable level

6:07and not overwhelm our MAC address tables is we simply

6:10just bill for the number of MAC addresses

6:12that the customer sent in into our network.

6:14So as traffic is originated and sent into the network,

6:17our devices are going to learn about the source MAC addresses.

6:20And when it doesn't know about the destination MAC address,

6:23it performs the exact same flooding

6:25that you would expect before.

6:26It's just flooded based on the S tag's VLAN.

6:29Of course, as return traffic is sent back, all of our devices

6:33are learning about that destination MAC

6:34address or that source MAC address as well.

6:37And that way it keeps these MAC addresses in their MAC address

6:39tables.

6:40And then next time we have to forward traffic between sites,

6:43it will go much quicker because we're not

6:45having to wait for ARP replies and such like that.

6:47So this is covering the actual frame walk of an 802.1ad

6:51or QinQ environment.

6:52The big thing to keep in mind is that the interfaces themselves

6:56are what the provider network device knows

6:58to inspect and look at the configuration of in order

7:01to actually set the S tag.

7:02It doesn't care about the C tag unless we explicitly

7:06configure it to only allow specific certain C tags.

7:09And there are some use cases for that

7:10that we'll eventually get into.

7:12For now, that is 802.1ad end-to-end.

7:15I hope this has been informative for you.

7:16And I'd like to thank you for viewing.

0:05Now here's the next thing that really catches newcomers

0:08to the service provider world off guard.

0:10We already thought we've learned every networking acronym there

0:13is to know because we came from the enterprise world,

0:15and what you find out very quickly is you haven't.

0:18The service provider world is an entirely different world,

0:21and there is plenty of alphabet soup

0:23out there for you to learn.

0:24Provider bridging is not an exception to that.

0:27There are some key terms and some key acronyms

0:30that you will absolutely need to commit to memory because this

0:32is what you'll read in textbooks.

0:34This is what you'll see on exams,

0:35and this is what you'll hear me say

0:37throughout the upcoming Nuggets that we

0:38have within this skill and many other skills that

0:40are centered around service provider networking.

0:42So let's keep going talking about some

0:44of the key terms and acronyms that you

0:46will encounter when you talk about provider

0:48bridging in the real world.

0:49Let's get going.

0:50Yep.

0:51There's no escaping it.

0:52We have some key terms that we have

0:53to learn about some jargon, some service provider world

0:56usages that you'll see.

0:57Whenever you join a service provider

0:59network for the first time, you will

1:01be overwhelmed with the number of acronyms and crazy things

1:05that they actually do.

1:06So this is where we're going to get

1:07started learning about our first service provider key terms.

1:11What we're looking at here is an ethernet virtual connection,

1:15or EVC.

1:16This is the service that we're actually trying

1:19to provide to our customers.

1:20What they would try and say is we just

1:22want a layer two connection for one site to the next,

1:25and we would hand them a pamphlet that

1:27says what you're really talking about

1:29is an ethernet virtual connection.

1:31This is what would be on their bill.

1:32We're selling them an ethernet virtual connection,

1:35and the entire network or the entire domain

1:38that we manage here is called the provider bridge network.

1:42That's what this entire pink section is.

1:44Everything that is under our control as a service provider

1:47and participates in the service provider

1:49bridging, or the EVC, this is part of the provider bridge

1:53network.

1:54Now, the device that we're going to be connecting to,

1:56the customer's device, this is called the customer edge,

2:00and this is probably familiar to you

2:02if you've ever worked with MPLS or MPLS layer 3 VPN.

2:06The terminology doesn't change a whole lot here.

2:08All of the customer's equipment that we actually connect to

2:11is the customer's edge device because this

2:14is the edge of their network.

2:16They have a whole bunch of devices on the inside of that,

2:19but this is the actual edge, and this

2:20is as far as we go when it comes to caring about what goes on

2:23in their network.

2:24The network devices that we are providing for them to connect

2:28to, or the devices that they think they are connecting to,

2:31is oftentimes referred to as the provider edge.

2:33But specifically, when we're talking about bridging,

2:36we are talking about the provider edge bridge.

2:40So these four devices here that my customers are connecting to

2:44are provider edge bridges.

2:47And specifically, the ports that they're connecting in on-- we

2:50see we've got these ports all that I'm highlighting right

2:52here--

2:53these are called customer ports.

2:56So we've got ge-0/0/0, ge-0/0/3, ge-0/0/0, ge-0/0/3, ge-0/0/0,

3:02ge-0/0/3, ge-0/0/0, and ge-0/0/3.

3:07All of the ge-0/0/0s and ge-0/0/3s on my PEBs are

3:12customer ports, whereas all of the devices that are

3:15interconnecting my provider bridges--

3:19that's a connection like right here between a provider edge

3:22bridge or a connection right here between the provider edge

3:25bridge in the core--

3:26these are simply called network ports, very simple.

3:31Now, lastly, we have in the center of our provider bridge

3:34network, we have these core devices.

3:36And if you recall, based on the frame law,

3:39these devices only care about the S-VLAN tags themselves.

3:43These devices will almost never ever, ever inspect the C tag

3:48in forward based on the C tag.

3:50These devices that are only in the center of the network

3:53and are forwarding S tag frames are oftentimes

3:57called to S-VLAN bridges because they only

4:01participate in the S-VLAN.

4:03They only care about the S tag on the ethernet frame itself.

4:06So these are some of the key terms about all

4:09of the components and moving parts that actually make up

4:12a EVC, an ethernet virtual connection,

4:15and this is all of the stuff that goes on in a PBN.

4:18We've got the PEBs.

4:19We got the provider bridges.

4:21We've got the S-VLAN bridges.

4:22We have customer ports, and we have network ports.

4:24So that's been the terms that you

4:26need to know about when you're actually talking about how

4:28to deploy Q and Q environment.

4:30I hope this has been informative for you,

4:32and I'd like to thank you for viewing.

0:00[MUSIC PLAYING]

0:05There are some more key terms that we

0:07need to talk about but we're not going to talk

0:09about them in this Nugget.

0:09What we actually have to do in this Nugget

0:11is set up the reason that we have more key terms that I'm

0:15about to define for you.

0:17What I'm really talking about here

0:18is what happens when a service provider has

0:21to forward frames to a different service provider?

0:24Or maybe a service providers business unit

0:27has to forward frames to a different business unit

0:30in the same service provider.

0:31What we're really talking about here

0:33is what happens when we have VLAN mismatches when those

0:36S-tag as we transmit S-tag data from one service provider

0:39network to a different service provider network.

0:41Let's talk about the scenario about what

0:43to do when there are two service providers in play

0:45within a single customer's ethernet segment.

0:48Let's get going.

0:49So this example has been great up until this point

0:51because we've used it to talk about how

0:53a service provider could provide an EVC to its customers.

0:57That way, a customer who has a location here in this city

1:01and maybe has a location here in the exact same city,

1:04they could provide pretty simply layer two connectivity

1:07from one site to the next.

1:09But what happens when customers start

1:11to spread out a little more?

1:12Maybe they're not in the same city.

1:14Maybe they're not even in the same state.

1:16Maybe they're not even in the same country.

1:18What happens then when the enterprise wants to actually

1:21still provide a layer two connectivity from one side

1:23to the next but now we don't actually have

1:26autonomy in their remote site?

1:29We now have to partner with other service providers

1:32and this could come into some more coordination issues.

1:34Here's how we can actually go about making this work

1:37and setting up the next Nugget where we talk about some more

1:39key terms that actually goes with deploying Q-in-Q Now,

1:42what we're working with is that we have a scenario where

1:45we have one service provider, I'll

1:47call the service provider one.

1:49And now, in this new box, we have a service provider two.

1:53Our customer is still the same.

1:54Well, actually are both of our customers are still the same.

1:56They still have the blue customer

1:58and the green customer.

1:59And they still have one site here and one site here.

2:01And they still want layer two connectivity

2:03from this device over here to this device.

2:06But what happens now is we have this particular issue here.

2:10The good news is, is in both service provider environments.

2:13If they're willing to work together and make this happen,

2:15they're still just going to use Q-in-Q. That's right.

2:19We're still only talking about forwarding traffic

2:21based on S-tags.

2:23The coordination problem that we run into oftentimes

2:26is that service provider one may give this customer

2:30the S-tag of 300.

2:34Whereas service provider two may give that customer

2:37the S-tag of 396.

2:40Just to make something random up.

2:42So as they send in their traffic,

2:44it may come in with a C-tag one more time of 110.

2:48It'll be arriving right here on this interface where

2:51the S-tag tag of 300 is applied and forward it out

2:54of this interface.

2:55Now, what has to happen is right here

2:57on this device that sits on the edge.

2:59A translation will have to occur.

3:02And this is as simple as performing a VLAN translation.

3:06It's just like NAT for IP addresses.

3:08We would explicitly configure this device

3:12that sits in the core to inspect anything with the S-tag of 300

3:17and dust outbound towards this network.

3:20Swap the 300 tag for 396 and vise versa.

3:26Any traffic that arrives inbound from this network

3:29with an S-tag of 396, swap it for 300

3:32and then go about performing the forward lookup.

3:34So from here, this service provider

3:36would be receiving an S-tag of 396

3:39because the core device that sits

3:41in the center already swapped out our S-tag of 300

3:44for the S-tag of 396.

3:46So in this device receives the S-tag of 396,

3:49it knows to perform the VLAN forwarding based on the S-tag

3:52And in this case, it may actually strip off that S-tag

3:55and forward the 802.1Q frame on to the customer in blue.

3:58So this is actually another major talking point

4:00about Q-in-Q. Q-in-Q actually set up

4:03the functionality to allow for changing the VLAN tags

4:08themselves.

4:08That's right.

4:09We're actually pulling off VLAN tags.

4:11We're stripping them off and then replacing them

4:14as they go on the fly.

4:15And the big thing that now we want to talk about, it makes

4:17sense when we explore this as a service provider

4:20to service provider communication.

4:22I mean, we've seen it already up until this point,

4:24where we had a service provider one, maybe this

4:26was something like AT&T. And then service provider two,

4:29maybe this is something like Verizon.

4:30It makes sense that they would never or rarely

4:33assign the exact same customer the exact same S-tag.

4:36And therefore, some translation would

4:38have to happen along the way to actually make

4:40this connectivity work.

4:42But what could actually happen is that these are actually

4:45the same service provider.

4:46That could actually happen and this is one business unit.

4:50And this is a completely separate business unit.

4:52It's unlikely that a large nationwide service provider

4:56has the exact same VLAN or the exact same numbering scheme

5:00or naming scheme from one state to the next.

5:02As traffic transits across the country

5:06even within the same service provider,

5:08there's a chance that it will leave the autonomous

5:10system or an autonomous boundary and transition

5:13into a different networking team's infrastructure

5:16and a translation would still need to occur in this case.

5:19So keep in mind that when you join the service provider

5:21world, yeah, absolutely, when you have a coordination

5:25attempt between two different service providers,

5:27there's probably going to be a translation that takes place.

5:30But if you're joining a large service provider that

5:33spans multiple geographies, there's

5:35still a pretty high chance that translation

5:37needs to take place in your provider bridging solution.

5:40So a cool thing about EVCs is that customers

5:44who span from one corner of the country to the other

5:47could still possibly receive an EVC solution

5:50through the coordination of multiple service providers

5:52working together and creating VLAN translations of the S-tag

5:56as they go on the fly.

5:57I hope this has been informative for you.

5:59And I'd like to thank you for viewing.

0:00[MUSIC PLAYING]

0:05In the previous Nugget, we introduced the concept

0:07of VLAN translation.

0:09And it makes a lot of sense-- that

0:10is one provider needs to send traffic

0:12to a different provider, but they're

0:14using two different S-VLAN tags, or S-tags.

0:17We need to coordinate the translation from one network

0:20to the next network and vise versa.

0:22So now what we're going to talk about

0:24is how does that translation actually occur,

0:26and what are the key terms that are centered around changing

0:29the actual VLAN tags themselves on these ethernet frames?

0:33Let's get going talking about the key terms centered

0:35around VLAN translation and, ultimately,

0:38how we can manipulate the actual tags themselves.

0:41Let's go.

0:42So in the previous Nugget, I made sure--

0:44or tried really hard, at least-- not to spoil or give away

0:47any of the key terms.

0:48But it's really important that when

0:50we talk about removing or changing VLAN tags,

0:53we really need to have these key terms drilled into our memory

0:57because these are actual words that service provider network

1:01engineers speak.

1:02These are the actual words that you

1:03will see on exam environments or read in textbooks.

1:06So make sure that you learn these words

1:09and commit them to memory when you're

1:10talking about things like service provider bridging

1:13as well as MPLS.

1:15You're going to see these words pop up one more time.

1:18The three words that are really coming into play

1:20here are pop, push, and swap.

1:24Let's start off with pop.

1:25What we're really talking about here

1:26is when this host, Docker30 here,

1:29sends a frame into the network, it gets tagged,

1:33and it comes all the way up to the edge.

1:35And now it's time to remove that S-tag

1:38so that only the C-tag remains.

1:40That is a pop operation.

1:42We're popping the top off.

1:43We're popping that outer tag, the S-tag,

1:46out of the ethernet frame itself,

1:48leaving only the C-tag behind.

1:50And then, we forward it on.

1:52That is a pop operation.

1:54Commit that to memory, because it's an important one to know.

1:57But what about when we added the S-tag frame on?

2:00The frame was sent via an 802.1Q trunk port up to our device

2:05and, at the time, it only contained the C-tag.

2:08Before it left our PEB, or provider edge bridge,

2:12we had to push a tag onto the device.

2:15This is the add operation.

2:17So under pop, I'll just go ahead and put this now

2:20for cleanliness sake.

2:20We've got the remove tag operation.

2:22Under push, we've got the add tag operation.

2:25And this is where we push the S-tag.

2:28Then, lastly, we have the swap operation,

2:31and that's what occurred right here.

2:33This is where we actually did kind of a pop-push.

2:36We popped the S-tag off, and then pushed a new S-tag on.

2:42They simplify that by calling it a swap.

2:44So in this case-- we set it up in the previous example--

2:46we had an S-tag of 300 that was pushed onto the frame

2:51as it arrived in our provider bridge network.

2:54We forwarded the frame based on VLAN 300 information.

2:58The S-VLAN bridge received it, and it

3:00knows, based on the configuration, that it's time

3:03to swap the frame.

3:05So it performs the swap operation,

3:07which under the hood, is popping 300 and pushing-- we pushed 396

3:12in the previous example.

3:14And then, the 396 frame moves forward

3:16into the new provider network.

3:18The provider edge bridge, or PEB, device in the new provider

3:21edge network performs the penultimate pop operation,

3:25leaving only the C-tag, and then forwards it

3:28into the customer's network.

3:29And that sets up the three different types

3:32of operations that you will encounter in the service

3:34provider bridging technologies.

3:36But here's the real kicker, now it's time

3:38to talk about it even a little bit more.

3:40We can take these three technologies

3:42and perform combo moves, so to speak.

3:45And you will also encounter these in the real world.

3:48So there is such a thing as pop-pop.

3:51This is where we remove the outer tag

3:53and also remove the inner tag.

3:56There is also pop-swap.

3:59This is where we remove the outer tag

4:02and swap the inner tag.

4:04There is a swap-swap.

4:06This is where we swap the outer tag

4:09as well as swap the inner tag.

4:12Now, I'll let you figure out what is a push-push.

4:15Go ahead and pause the video and take a moment

4:17to think about it.

4:18[MIMICKING "JEOPARDY" THEME]

4:21This is where we add both an inner tag and an outer tag

4:25to an Ethernet frame.

4:27So this is covering the key terms

4:28that you need to know about when it actually comes time

4:30to translate a VLAN S-tag or C-tag.

4:34We have the ability to control all of the information

4:37as it traverses through our entire network.

4:39So we can not only pop the S-tag and swap the S-tag

4:42or push as S-tag, we can also manipulate the C-tag

4:45if we actually have a use case for doing that.

4:47And these are the three key terms that you really

4:49need to commit to memory when it comes time

4:51to talk about VLAN translation.

4:52I hope this has been informative for you,

4:54and I'd like to thank you for viewing.

0:05Now, this last Nugget is a little bit

0:07of lagniappe for you.

0:08It's nothing much more than good-to-know information

0:11there's not a whole lot that you really

0:13need to dig too deep into this.

0:14But the big thing that I wanted to set you up for

0:17is really what happens when you go out there in the real world

0:19and start working in service provider networks,

0:21or you go beyond the JNCIS and you go

0:24towards the JNCIP or the JNCIE.

0:26One of the things that you'll find out really quick is that

0:29802.1ad and QinQ is not the most widely deployed service

0:34provider-bridging technology that's out there.

0:36What you actually may run into is something called VPLS.

0:38Let's talk a little bit more about what

0:40VPLS does for us at the end of the day in a service provider

0:43network.

0:43Let's go.

0:44Now, the last thing I wanted to talk about here

0:46was VPLS, because it is true that in the actual service

0:50provider world, this is becoming the more prominent way

0:53to provide Layer 2 private VPN technologies to our customers.

0:57We're talking about a different way

0:59to perform EVCs, or Ethernet Virtual Connections.

1:02What really goes on here is that we

1:04have a logical infrastructure here

1:07that provides a backbone that looks something like this.

1:10To our customers, they only see this as a Layer 2 broadcast

1:14segment, not really any differently

1:17than QinQ technologies.

1:19But what really goes on here, is we're not eating up

1:21all of our VLAN space.

1:22We're not actually performing QinQ tunneling.

1:26What we're really doing here is leveraging

1:28functionalities of MPLS, as well as the IGPs themselves,

1:33like OSPF and ISIS.

1:36In order to actually deploy VPLS,

1:38well, you're really starting to break

1:39into not only JNCIP technologies and topics, we're actually

1:43talking more into JNCIE technologies and topics,

1:47because it is heavy, heavy, heavy, on MPLS and traffic

1:51engineering the correct label switched paths.

1:54We haven't talked about all those yet.

1:56We will talk a lot about the MPLS, label switch paths,

1:59and traffic engineering using the RSVP protocol, as well

2:03as variations of these IGPs, ultimately resulting in CSPF.

2:08Don't worry about this too much.

2:09We're going to talk all about it.

2:11And it will set you up for success

2:13when you start to get into VPLS, should your studies actually

2:16take you that far.

2:17Just know that VPLS is an alternative to 802.1ad

2:21and QinQ, and it relies heavily on MPLS.

2:24But from the customer's point of view,

2:26it still looks the exact same.

2:28It's like one gigantic ethernet broadcast network,

2:31where they can see all of their different sites and VLANs

2:34and connect to each other through Layer 2 technologies

2:37as a flat network.

2:38That's just a brief primer on what VPLS does.

2:41It really just leverages MPLS in order

2:44to provide the exact same EVC as QinQ.

2:47I hope this has been informative,

2:48for you and I'd like to thank you for viewing.

0:05I know you're dying to see configurations

0:07right now, because you're like, oh, oh, let's see it in action.

0:09Let's make some packets flow.

0:10And I am too.

0:12Deploying these configurations on a Juniper device

0:15is kind of a big thing.

0:16There's a lot of stuff that's going on here.

0:18And that's why we've got an entire skill dedicated

0:20to the deployment of service provider

0:22bridging coming up next in this playlist.

0:24For now, we needed to introduce all of these core concepts

0:28and really lay the foundation for the fact

0:31that the service provider world is totally different.

0:33We're now looking at networking from an entirely different lens

0:37than we may have been when we were in the enterprise world.

0:39So we've introduced the core concepts

0:41of what provider bridging does.

0:43What problems did it really solve with 802.1Q?

0:46And then we talked about, how is the 802.1ad system really

0:51deployed throughout this enterprise,

0:52how does a frame flow from one hop to the next,

0:56and then even talked about some things like,

0:57what do we do when there's multiple service providers

1:00in the mix here.

1:00And we talked about then we could do things

1:02like VLAN translation.

1:04So this sets up the foundations for service provider networking

1:07and service provider bridging.

1:08I hope this has been informative for you,

1:10and I'd like to thank you for viewing.