[c-nsp] small cisco as ethernet bridge, IPv6 broken, sadness

[Arie Vayner (avayner)]

Joe,

Did you check for MTU issues?
IPv6 has different MTU requirements than IPv4, and the setup you are
describing is prone to MTU issues due to the reduced MTU on the L2
transport.

Arie

-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net
[mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Joe Abley
Sent: Wednesday, September 09, 2009 01:37
To: cisco-nsp at puck.nether.net
Subject: [c-nsp] small cisco as ethernet bridge, IPv6 broken, sadness

I have the following setup in place for remote access to an exchange  
point in Toronto:

  juniper J2320 router
          |
     cisco bridge 1
          |
          |          ) telco-provided
   -------|-------   ) layer-2
          |          ) transport
          |
     cisco bridge 2
          |
     exchange point
          |
      peer router

The telco transport in question is DSL at the top and ethernet at the  
bottom. The top bridge is connecting local ethernet to ethernet over  
ATM over whatever, so it's a glorified DSL modem; the bottom bridge is  
there to clean the traffic that would otherwise flood to the exchange  
(e.g. to eliminate other weird, foreign-sourced frames that seem to  
appear from the telco layer-2 service from time to time).

For IPv4, this all works gloriously.

For IPv6, not at all.

The bridges are both cisco 2600 devices with "no ip routing". Some  
config fragments below. The top bridge has a DSL WIC and I'm bridging  
between that and a VLAN configured on an FE port; the bottom bridge  
has a pair of FE ports, and I'm bridging between them with no VLANs.  
There is a single BVI configured on "cisco bridge 2" just to give me  
an address to ssh to. I tried removing that and managing the box via  
the console, but no change.

Is there something fundamental I'm missing, here? Why should a  
transparent bridge behave differently with IPv4 than it does with IPv6?


Joe

! cisco bridge 1

cisco 2620 (MPC860) processor (revision 0x102) with 61440K/4096K bytes  
of memory.
System image file is "flash:c2600-ik9o3s3-mz.123-26.bin"

interface ATM0/0
  no ip address
  no ip route-cache
  no atm ilmi-keepalive
  dsl operating-mode auto
!
interface ATM0/0.1 point-to-point
  no ip route-cache
  bridge-group 1
  pvc 0/35
   encapsulation aal5snap
  !
!
interface FastEthernet0/0.200
  encapsulation dot1Q 200
  no ip route-cache
  bridge-group 1
  bridge-group 1 spanning-disabled
!
bridge 1 protocol ieee


! cisco bridge 2

cisco 2621 (MPC860) processor (revision 0x102) with 61440K/4096K bytes  
of memory.
System image file is "flash:c2600-ik9o3s3-mz.123-26.bin"

interface FastEthernet0/0
  description facing the telco
  speed 100
  full-duplex
  bridge-group 1
  bridge-group 1 spanning-disabled
!
interface FastEthernet0/1
  description facing the exchange point
  bridge-group 1
  bridge-group 1 output-pattern-list 1100
  bridge-group 1 spanning-disabled
!
interface BVI1
  description a way to manage the bridge, v4-only is fine
  ip address x.x.x.x y.y.y.y
!
bridge 1 protocol ieee
bridge 1 route ip

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