[c-nsp] IPv6 BGP peering problem

[Pekka Savola]

Hi,

On Sat, 20 May 2006, Dave Mifsud wrote:
> The peer is over an IPv6 only-over-IPv4 tunnel. I had tried lowering my
> end IPv6 MTU to 1280, but to no avail.
>
> The config of the tunnel interface currently reads so:
>
> interface Tunnel202
> no ip address
> ipv6 address 2001:DB8:FF00:1::D/126
> ipv6 enable
> ipv6 mtu 1280
> tunnel source Loopback12
> tunnel destination 192.0.2.1
> tunnel mode ipv6ip

If it's a MTU problem, the MTU needs to be lowered at the other end as 
well.  Based on the log (if the debug output isn't substantially 
different from the before), that's not the likely cause.

>From the snippet below, it seems likely that both endpoints are trying 
to establish the session simultaneously.  The other endpoint seems to 
think you already have an established session because it's sending you 
ACK of a non-established session ("ACK while in LISTEN").

So, my suspicion is that the problem is at the other end of the 
session, maybe a bug or hard-clearing of BGP sessions there might 
help.

>>> 11:43:20: TCP: sending SYN, seq 1143279122, ack 0 11:43:20: TCP0: 
>>> Connection to 2001:DB8:FF00:1::E:179, advertising MSS 4390 
>>> 11:43:20: TCP0: state was CLOSED -> SYNSENT [16991 -> 
>>> 2001:DB8:FF00:1::E(179)] 11:43:20: TCP: input 
>>> 2001:DB8:FF00:1::E(179) -> 16991: ACK while in LISTEN 11:43:20: 
>>> TCP: sending RST, seq 1143279123, ack 0