[c-nsp] ISIS Problem

[Ibrahim Abo Zaid]

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