ISIS IPv4 Workbook 1

let’s get cracking with our first workbook for ISIS

ISIS TASK 1

As we can see here we have our first task you’ve been provided with the IPv4 addressing So all the configurations for that are done So there’s basic connectivity between each pair of devices.

So we need to implement ISIS across the multi area network and we need to ensure proper route exchange and design the segmentation between levels 1. And level 2 areas.

what we’re gonna do with this is we’re going to decide what we’re going to have as our levels. as CE 2 is at the end of the area and It’s not linking with, another area, this can be a level 1 device and exactly the same with CE 1 So that can also be a level 1 device.

However, if we was to select PE 1 as a level 1 device, then that would mean it can’t form a neighbor ship with PE 22 because that’s in a different area. So we have a couple of options available, we can either set it as a level 2 device only, which is absolutely fine or we can set it as default to be a level 1 level 2 router. Now, if we do that and that’s a normal implementation, you’ll see that quite often.

Then what that would mean is that between CE 1 and PE 1, you will have both a level 1 membership. if we set this to level 1 anyway that’s all you’ll have, but you’ll still be getting  updates still being tried to send out for level 1 towards CE 1.

To try and minimise the amount of traffic again with this particular scenario, it’s not a very big lab, but in a bigger production network you may decide that you don’t want to be propagating in additional level information just for it to be dropped on the other side, so we will set this as a level 2 router 

and exactly the same for PE 22, and 23 as these are both basically ABRs, on their respective areas. We   we have a PE 22 connected from area one to area two and PE 23 connecting from area 0001 to area 0003 so we can set these as level 2 devices 

We put that as a level 2 and that as a level 2 because they’re direct neighborships in different areas towards PE 1 and towards PE 4. Don’t need to have level 1 information at all and again with PE 4 

And but we can just do level 1  between  PE 4 and CE 4  let’s implement that and see if we can get this up and running.

let’s start on CE 2 We’ll work from left and work our way across 

ISIS Conifguration

Okay It’s going to enable mode   the first thing we need to do is get our ISIS 

neighborship up and running, and that’s going to be on Router CE 2.  we need to set our ISIS Net address up This is for area 49.0002 So let’s go into configuration mode 

router isis 1
net 49.0002.0000.0002.00
is-type level-1
passive-interface Loopback0

That means while the routes for loopback 0 will be advertised it won’t attempt to form any particular sort of neighborships. So that’s all we really need to do just to get IS IS up and running What we need now is to add in the  physical interface that’s going to connect  CE 2 to  CE 1.

interface GigabitEthernet2
 description link to CE1
 ip address 10.10.21.2 255.255.255.0
 ip router isis 1
 negotiation auto
 no mop enabled
 no mop sysid
 isis circuit-type level-1

let’s now jump on to CE 1. And do the same thing We’ll do the membership between  CE 1 and  CE 2 first 

router isis 1
 net 49.0002.0000.0001.00
 passive-interface Loopback0

interface GigabitEthernet1
 description link to PE1
 ip address 10.10.11.1 255.255.255.0
 ip router isis 1
 negotiation auto
 no mop enabled
 no mop sysid
 isis circuit-type level-1
!
interface GigabitEthernet2
 description link to CE2
 ip address 10.10.21.1 255.255.255.0
 ip router isis 1
 negotiation auto
 no mop enabled
 no mop sysid
 isis circuit-type level-1

Now, the neighborship is obviously not formed yet because we’ve not put the g2 interface into the actual ISIS router protocol

We see our adjacency has now come up So that’s fantastic  We can do a do show  IP route ISIS And we can see that it’s learned the loop back here from CE 2 So that’s good we have our first neighborship up We’ll jump along now to the next device and sorry the to the next neighborship, which is on g1 and we’ll get that up and running as well 

CE1#show ip route isis
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       

Gateway of last resort is not set

      2.0.0.0/32 is subnetted, 1 subnets
i L1     2.2.2.2 [115/10] via 10.10.21.2, 06:11:51, GigabitEthernet2

So let’s go into  interface g1  and let’s do our ISIS configuration

CE1#show isis nei
CE1#show isis neighbors 

Tag 1:
System Id       Type Interface     IP Address      State Holdtime Circuit Id
CE2             L1   Gi2           10.10.21.2      UP    9        CE2.01             
PE1             L1   Gi1           10.10.11.11     UP    7        PE1.03             
CE1#

So that is now  CE 1 done now let’s jump on to PE 1 which is our Cisco IOS XR device and get ISIS running on this  

router isis 1
 net 49.0002.0000.0011.00
 address-family ipv4 unicast
 !
 interface Loopback0
  passive
  address-family ipv4 unicast
  !
 !
 interface GigabitEthernet0/0/0/0
  circuit-type level-2-only
  address-family ipv4 unicast
  !
 !
 interface GigabitEthernet0/0/0/1
  circuit-type level-1
  address-family ipv4 unicast
  !
 !
!

And let’s sit there now

So let’s do 

router ISIS one 

Okay Let’s do our next statement. So it’s gonna be forty nine dot zero zero  two 

dot zero zero zero zero dot zero zero zero zero. Actually it’s still eleven dot zero zero.  that’s our next statement. That’s fine  what we need to do we need to add in the IPv4 address family as well. The address family IPv4 unicast 

So we need to globally activate it And let’s do our  interface loop back zero and we’ll set that to passive 

And we also need to add the interface as well into the IPv4 address family 

To address family IPv4 unicast 

Okay excellent. So now we’ve added in the loopback We need to add in our  interfaces. So gig one is going to be a level one interface 

So let’s do interface g zero slash zero slash zero slash one 

And we’re going to do the address family as well but we need to set the actual  circuit type as well. So let’s do the circuit type 

and we’ll do 

level one  and the address family is going to IP b for unicast  Okay 

Now let’s jump on to the  interface that goes to p e 22 which is gig zero 

So interface g zero slash zero slash zero  and the circuit type. At this time this is going to be a level two because you can’t do a level one adjacency with a device in a different area 

So level two, and the address family is I p v for  unicast and let’s commit that

Let’s have a look at our 

ISIS configuration So we have our net statement We have the global  address family IPv4 unicast. We have our interface loop back zero. It’s passive, so it won’t attempt to try and form any lever ships on that. We’ve again  added in the IPv4 unicast  Gig of ethernet zero We’ve set that to level two with the address family and gig of ethernet one We’ve set that to level one. Okay.

So on CE one there we go We see that the  Labororship has come up so that’s great So let’s jump on to PE 22 now and see what we can do with this So with PE 22, we have gig zero and gig one They are both  level two 

Connections  and it’s in area one.  let’s get cracking with this one 

So let’s go 

Comf t, and let’s do  router ISIS process one. But the process is only the process ID is only locally significant. So yeah you can use any process ID that you want You don’t have to keep the same one but just when you’re lagging sometimes it’s easier to just do that 

And then we’re going to do address family  IPv4 unicast to enable it globally  and we’re going to interface  loop back zero It’s gonna be passive 

Okay That’s fantastic And we just need to add in the address family again, the address family IPv4 unicast 

Brilliant.  we know that both gig ethernet zero and gig ethernet one are both going to be level two So zero and one. So let’s do interface  g zero slash zero slash zero slash zero. And the circuit type is  sorry level two rather  is going to be level two 

and the Just family is going to I b e v four unicast  Okay 

And interface g zero slash zero slash zero slash one 

And the circuit type, again is going to be  level two 

And your dress family is I p v four unicast  Okay Let’s commit that 

Alright Fantastic Let’s do a show ISIS 

neighbor  And we can see that we already have a neighbor ship with e e one We can see that it’s a level two neighbor ship and that’s exactly what we’re expecting to see Let’s jump on to p e 23. P 23 is an iOS XE router. So let’s do g. So again g one and g two They’re both going to be  level two. So let’s jump on to that 

So go enable  comptee 

and let’s do a 

router 

ISIS 

one  Let’s do a net statement of forty nine dot zero zero zero one 

zero zero zero zero zero zero zero 

23  two zero 

Okay And let’s do 

passive interface loopback zero 

 that’s the interface in So we we need to add in now the actual  interfaces the physical interfaces And just before we do that I just want to quickly check p e 22  again 

Just to double check what I put down as the IS IS Okay Yeah I put that down This is the correct. neighborship No That’s fine 

Brilliant stuff  let’s jump back on p 22, and let’s get out of that, and let’s go into interface g one 

and ISIS 

Type oops It won’t want 

So let’s put that back in again 

So ISIS 

circuit type  Is level two 

and IP router 

ISIS process one 

Okay And let’s go on to interface  g two and we see we have our neighborship with p 22 already which is great. So g two  and it’s going to be ISIS circuit type is going to be level two 

and IP router 

ISIS process one 

 that’s p e 22 

Done as well and p e 23 are both done. Brilliant 

Okay Let’s jump on to the 

next router 

and see what’s going on with that one

Okay We did see a neighbor ship come up on p e 23 So it’s possible I may have already configured this one Let’s have a look 

Alright Okay. So I have already enabled this which is fine It’s supposed it just keeps the, the router the 

video for being exceptionally long. So again exactly what we expect. So gig ethernet  two, we’ve set that to level two, and we’ve also set  gig ethernet one which is going to CE one to level one. We have our passive interface there, and we have our next statement which is exactly what we want.  let’s do a show ISIS neighbor and see what’s happening with that So we’ll have our level two neighborship  with p e 23  Which is exactly what we expect.

Okay In that case please let’s jump on to a c four 

And so show iOSize neighbor  You see nothing Okay. It should run 

section  ISIS   we have no ISIS isn’t it Let’s set this one up then So confit 

And let’s go into router 

ISIS one 

and the next statement  is going to be forty nine dot zero zero zero three zero zero zero zero zero 

Forty four 

There we go Alright Sweet. And let’s do  passive interface loopback zero 

Okay And now let’s go on to our 

physical interface, which is g1

Interface g 1 

and  we do

ISIS  circuit type  level 1 

and IP router  ISIS  process ID 1 

Okay. Fantastic. And then we see we have our adjacency has now come up to 

PE4

 we’ve now  done the first task.

we need to do our show commands as we’ve done the first task we’ve been we’ve that are individual area neighbor our levels, and we’ve got the neighborships up and running. So what we need to do now is to use our show commands  to see whether or not   we have our neighborships up and whether   we are actually learning a route. So let’s jump on to let’s say PE 1 

and let’s do a 

show ISIS database 

PE 1 has a neighborship on the level 1 and the level 2 we have two different databases. We have level 1 database and we have the level 2 database as well. And we can see the actual  neighbor that we have on that If we want to have a look at the details which we can 

and it’ll show us more detail of the actual level 1 and level 2  routes users like private instance. We can see that we’re learning the let’s say the 1.1.1.1 address. We can see the metrics that is coming from, and 

the interfaces there that we’re learning it from and the hashes for the actual  LSP updates itself.  there’s a lot of information. Let’s have a look at show route 

ISIS to see what we’re learning.  we can see we’ve got the loopback of   CE 1 We have the loopback of of  CE 2 under pair. The loopback of PE 4 

So we we’re getting a lot of the loopbacks and a lot of the routes so that’s absolutely great That’s exactly what we expect to see. Let’s have a look on  PE 22 now 

Okay Let’s do a 

show ISIS neighbor 

 we have our two neighborships up and running They’re both level 2 which is what we wanna see. Show, show route ISIS

Again we can see that we’re we’ve got the loopbacks in there so that’s looking exceptionally good. of of good note here is that if I’m gonna say we have the loopback  of CE 4 and PE 4 in there So CE 4is PE 4. So we have the loop back so everything’s going great in that regard. Let’s have a look on  CE 1 the iOS-XR image so CE 1 That was  this device here remember this only has a level 1 adjacency with PE 1 

So let’s have a look here So let’s do a Show IP interface brief 

So the loopback 1.1.1.1 Okay But we we’ve seen that  here So that’s been learnt 

on PE 22

show IP route  ISIS

And it’s been learnt as well on PE 23. So even though the membership between CE one and PE one is level one only 

PE 1 has taken the level 1 routes and is propagated over to PE 22 and PE 23, and it will be propagated back over to PE 4 as well So that’s the exact, behaviour we expect to see However what we was interested in was CE 1  So let’s have a look at CE 1 and see what it knows. So let’s do a show  IP route  ISIS 

the only route that it’s learned through ISIS is  the loopback of  CE 1 and the loopback of PE 1 It’s not learned anything else It’s not learned  any of the level 2 routes all it’s learned to do the level 1 routes This is a bit of a gotcha when you’re dealing with, especially iOS-XR

is that it while it will take level 1 routes and propagate them into level 2  it doesn’t do it the other way around so we need to fix that But that is for another episode which will be coming up after this.