Cisco ENCOR (350-401): VXLANs

[Music] hey welcome back to the channel everybody this is kevin and in this week's video we're going to take a look at a new topic on the cisco encore exam it's exam number 350-401 and the topic we're going to be addressing is vx lands virtual extensible lands we're going to see that we can have many more vx lands as compared to vlans and we're going to see that that vx lane can actually span a layer 3 boundary that's right we can have a broadcast domain that's spanning a layer 3 boundary kind of amazing and if you take a look at the encore blueprint you'll see that you need to be able to explain vxlans no configuration necessary and that's what we're going to accomplish in this video i want to give you a solid understanding of the theory behind vxlands and as always if you enjoy this video please do me a favor click that like button and subscribe so you don't miss any of our weekly content oh and one other thing if you enjoy this content stay to the very end of the video because i'm going to be giving you some discount links where you can pick up our new ccna encore and a narcy video training series now let's jump into this video on vxlans with traditional ethernet switches we can support a little over 4 000 vlans the reason is the vlan field is 12 bits long it's going to give us just over 4 000 vlans but in today's networks where we might have a data center with lots of virtualization and need to isolate several virtual machines from other virtual machines we could easily run out of vlans well the great news is virtual extensible lands or vx lands can come to the rescue they let us have over 16 million different identifiers instead of just 4 000 and the way vxlans can do that is by encapsulating our layer 2 or even layer 3 traffic and adding a vxlan network identifier that's called a vni and this vni field is 24 bits long that's what gives us those 16 million plus vxlan network identifiers and those vx lands can run over our existing physical network infrastructure the existing physical network infrastructure is referred to as an underlay network here we see 12 different switches and they're physically connected as you see here and this makes up the underlay network but we could create logical tunnels between specific switches to create an entirely different topology here we're using that same physical underlay network but we're logically creating tunnels between select switches to create a totally different topology and that's our overlay network and we typically see this in data centers where we use a spine leaf design we've got our nodes like our servers connecting to leaf switches and those leaf switches they interconnect by going through a spine the spine switches allow any leaf switch to get to any other leaf switch in only a single hop we just have to go through one spine switch because every leaf switch is connected to every spine switch and the device that does our vxlan encapsulation is called a virtual ethernet module or a vm and each vim has an ip address it could have more than one but it's got at least one ip address that we're going to use to communicate over this routed network and the ip address it's assigned to a special interface called a vtep which stands for vxlan tunnel endpoint and each vtep is associated with one or more vnis and vteps on different switches they can temporarily bring up a tunnel and pass traffic between themselves by the way another benefit that vxlans give us is that if we're sending traffic over a port channel where we've got multiple links making up a single logical link instead of just using one link the vxlan switches know how to load balance that traffic across all of the different links in the port channel that can dramatically reduce congestion in the data center but an issue we have is what do we do with traffic for which we don't know the destination i mean on a regular switched infrastructure a switch that doesn't know how to get to a destination it's going to send out an arp broadcast perhaps what about multicasts what about unknown unicasts what if we don't know where somebody lives how do we get to them well for that type of traffic called bum traffic for broadcast unknown unicast and multicast we've got different approaches for handling that but we're going to consider in this example using multicast that's a very popular approach what we can do is have these different vteps join a multicast group now you might be wondering do we have to have a multicast group for each vni and no we don't we could have multiple vni's belonging to the same multicast group because the vims themselves they're going to look at that vni identifier before sending the traffic out and you can see even though it received it over this multicast group it's going to see that oh yeah this is destined for a different vni i don't send it out of this port so it's totally fine to have multiple vni's associated with the same multicast group let's walk through an example of how this is going to work and the table you see on screen that table is being maintained by leaf switch 1 leaf sw one and what we want to do here is we want server one to communicate with server two how do we do this well server one is gonna send out an arp broadcast because it knows it wants to get to 10.1.1.2 but it doesn't know the mac address so it sends out an arp broadcast and when that frame goes into leaf switch one it's going to make an entry in its table that says hey i just learned that the always mac address lives off of port ethernet one slash one and that switch also has a mapping table that says vlan 10 to which server one belongs maps to vni one zero zero zero one zero so now we have a vni identifier not just a vlan identifier and the way we're going to get to that is go out of ethernet one slash one well we just sent broadcast traffic into this leaf switch one what's it going to do with that well for that bum traffic remember broadcast unknown unicast and multicast we're going to send that out to a multicast group that our other switch is joined and leaf switch 3 sees that because it's a member of that multicast group we're pretending that the group number is 239.1.1.10 when it gets that broadcast arp sent via multicast it's going to flood it out all of its other ports so it's going to go down to server 2 and server 2 says yep that's me and it says my mac address is the old b's mac address and it goes back to leaf switch 3 and switch 3 now knows that the 10.1.1.200 ip address with the all bees mac address lives off of port ethernet one slash one so it's going to respond to the other vtep and say hey if you want to get to the albus mac address come to me come to 192.168.1.33 that's my vtep ip address and it sends that information over to leaf switch 1 and leaf switch 1 is going to make an entry in its table it says if i want to get to the albe's mac address which lives in vni 1 0 0 0 1 0 i want to go to a vtep ip address of 192.168.1.33 and it's going to send the result of the all-bees mac address down to server 1. so now when server 1 wants to communicate with server 2 it's going to send traffic to a destination ip address of 10.1.1.200 which by the way is in the same vlan even though we're separated by a router it's going to say i want to go to that ip address with the all b's mac address and leaf switch 1 is going to say according to my table the obs mac address is available via vtep 192.168.1.33 so leaf switch one is going to form a vtep tunnel with leaf switch three it's gonna send that traffic over there and leaf switch three is gonna send it out to server two and that's a look at how vxlan communication is gonna be able to allow different devices that live on the same subnet the same vlan to communicate with one another across a routed network and it's very useful in the data center to have all those extra identifiers because as we discussed we could run out of vlans but we're probably not going to run out of vxlan network identifiers

Channel: Kevin Wallace Training, LLC

Views: 21,704

Rating: 4.9764705 out of 5

Keywords: cisco, CCNA, CCNP, CCIE, nears, 200-301, 350-401, 300-410, vxlan, vxlans, data center, vlan, vlans, #kwtrain

Id: SnnNrXtIc1c

Length: 8min 23sec (503 seconds)

Published: Wed Aug 26 2020