[c-nsp] ISIS Problem

[Yuri Bank]

Your configuration looks invalid. An ISIS router should only be part of a single area. This is different from OSPF, where a router can be in multiple areas.

It seems like R1 is advertising the default route it receives from R2 to R3, and R3 to R2. This wouldn't happen if R2 and R3 were in the same area, or if one of them didn't have a a L1 adjacency with R1.

To correct this reduce R3 and R2 to a single area ( 0001 ) and then set level 2 only on the links between R3 and R2. 

In interface configuration mode,
isis circuit-type level-2-only 




--- On Mon, 8/17/09, Ibrahim Abo Zaid <ibrahim.abozaid at gmail.com> wrote:

> From: Ibrahim Abo Zaid <ibrahim.abozaid at gmail.com>
> Subject: [c-nsp] ISIS Problem
> To: "cisco_nsp" <cisco-nsp at puck.nether.net>, cisco at groupstudy.com
> Date: Monday, August 17, 2009, 1:47 PM
> Hi All
> 
> I have a problem with the below ISIS toplogy , All ADJ of
> R1 are L1 and
> interface between R2 is in A2 from R2 side and in A3 side
> from R3 side
> so R2 and R3 have L2-ADJ betwene them , as expected both R2
> and R3 send LSP
> with ATT bit set so R1 has 2 L1 default routes point to
> both R2 and R3 , the
> wired result there is L1 on both R2 and R3 points to R1 !!
> but R1 don't set
> ATT bit in its LSP
> 
> do you explainsation why R1 sends this default route ? and
> how we can stop
> it
> 
> Topology
> 
> R2--------L-1------------
> |               
>           |
> |               
>           |
> L2       A-1     
>      R1
> |               
>           |
> |               
>           |
> R3---------L-1-----------
> 
> Configuration
> 
> R1
> 
> !
> interface Serial1/0
> description to R2
>  ip address 10.10.12.1 255.255.255.0
>  ip router isis
>  encapsulation ppp
> !
> interface Serial1/1
> description to R3
>  ip address 10.10.13.1 255.255.255.0
>  ip router isis
>  encapsulation ppp
> !
> router isis
>  net 49.0001.0000.0000.0001.00
>  is-type level-1
> 
> 
> R2
> 
> interface Serial1/0
> description to R1
>  ip address 10.10.12.2 255.255.255.0
>  ip router isis
>  encapsulation ppp
> !
> interface Serial1/1
> description to R3
>  ip address 10.10.23.2 255.255.255.0
>  ip router isis 2
>  encapsulation ppp
> !
> router isis 2
>  net 49.0002.0000.0000.0002.00
>  is-type level-2-only
> !
> router isis
>  net 49.0001.0000.0000.0002.00
>  is-type level-1
> 
> 
> R3
> 
> interface Serial 1/0
> description to R1
>  ip address 10.10.13.3 255.255.255.0
>  ip router isis
>  encapsulation ppp
> !
> interface Serial 1/1
> description to R2
>  ip address 10.10.23.3 255.255.255.0
>  ip router isis 3
>  encapsulation ppp
> !
> router isis 3
>  net 49.0003.0000.0000.0003.00
>  is-type level-2-only
> !
> router isis
>  net 49.0001.0000.0000.0003.00
>  is-type level-1
> 
> 
> Logs
> -------
> 
> 
> R1#sh clns neighbors
> System Id     
> Interface   SNPA       
>         State  Holdtime  Type
> Protocol
> R2         
>    Se1/0   
>    *PPP*         
>      Up     22 
>       L1   IS-IS
> R3         
>    Se1/1   
>    *PPP*         
>      Up     23 
>       L1   IS-IS
> 
> 
> R2#sh clns neighbors
> Area 2:
> System Id     
> Interface   SNPA       
>         State  Holdtime  Type
> Protocol
> R3         
>    Se1/1   
>    *PPP*         
>      Up     28 
>       L2   IS-IS
> Area null:
> System Id     
> Interface   SNPA       
>         State  Holdtime  Type
> Protocol
> R1         
>    Se1/0   
>    *PPP*         
>      Up     26 
>       L1   IS-IS
> 
> 
> R3#sh clns neighbors
> Area 3:
> System Id     
> Interface   SNPA       
>         State  Holdtime  Type
> Protocol
> R2         
>    Se1/1   
>    *PPP*         
>      Up     22 
>       L2   IS-IS
> Area null:
> System Id     
> Interface   SNPA       
>         State  Holdtime  Type
> Protocol
> R1         
>    Se1/0   
>    *PPP*         
>      Up     28 
>       L1   IS-IS
> 
> routing tables
> -----------------
> 
> R1#sh ip route isis
> i*L1 0.0.0.0/0 [115/10] via 10.10.13.3, Serial1/1
>            
>    [115/10] via 10.10.12.2, Serial1/0
> 
> R2#sh ip route isis
> i L2    10.10.13.1/32 [115/20] via 10.10.23.3,
> Serial1/0
> i L1    10.10.13.0/24 [115/20] via 10.10.12.1,
> Serial1/0
> i*L1 0.0.0.0/0 [115/20] via 10.10.12.1, Serial1/0
> 
> 
> R3#sh ip route isis
> i L1    10.10.12.0/24 [115/20] via 10.10.13.1,
> Serial1/0
> i L2    10.10.12.1/32 [115/20] via 10.10.23.2,
> Serial1/1
> i*L1 0.0.0.0/0 [115/20] via 10.10.13.1, Serial1/0
> _______________________________________________
> cisco-nsp mailing list  cisco-nsp at puck.nether.net
> https://puck.nether.net/mailman/listinfo/cisco-nsp
> archive at http://puck.nether.net/pipermail/cisco-nsp/
>