TCP IPv4 connections problem

[Nicolas DEFFAYET]

Hello,

I have a very strange problem on a router (R1): it stop to reply to TCP
IPv4 connections on one of its network interfaces after a random time
but it don't stop to reply to TCP IPv6 connections and ICMP IPv4/IPv6.

The network is composed of 3 routers with the same hardware and software
(FreeBSD 5.0): R1, R2 and R3.

Interfaces on R1:
ti0: to R2
ti1: to R3
ti2: to LAN1

Interfaces on R2:
ti0: to R1
ti1: to LAN2

Interfaces on R3:
ti0: to R1
ti1: to LAN3

Each interface have both IPv4 and IPv6 address.

R3 <-> R1 <-> R2


When the problem occur (between 3 and 24 hours after reboot):

LAN3 <-> R3: ICMP IPv4/IPv6 and TCP IPv4/IPv6 is OK
LAN3 <-> R1: ICMP IPv4/IPv6 and TCP IPv6 is OK, TCP IPv4 is not OK
LAN3 <-> R2: ICMP IPv4/IPv6 and TCP IPv4/IPv6 is OK
R3 <-> R1: ICMP IPv4/IPv6 and TCP IPv6 is OK, TCP IPv4 is not OK
R3 <-> R2: ICMP IPv4/IPv6 and TCP IPv4/IPv6 is OK
LAN1 <-> R1: ICMP IPv4/IPv6 and TCP IPv4/IPv6 is OK
LAN2 <-> R1: ICMP IPv4/IPv6 and TCP IPv4/IPv6 is OK
LAN2 <-> R2: ICMP IPv4/IPv6 and TCP IPv4/IPv6 is OK
R1 <-> R2: ICMP IPv4/IPv6 and TCP IPv4/IPv6 is OK


When i try to establish a TCP IPv4 connection directly to R1 through the
ti1 interface of R1 it dont work, but when i try to establish a TCP IPv4
connection directly to R1 through the ti0 or ti2 interface of R1 it
work. I can establish from R3 a TCP IPv4 connection directly to R2
through R1.


Do you have an idea how fix the problem ?


Thanks

Best Regards,

-- 
Nicolas DEFFAYET, NDSoftware
NDSoftware IP Network: http://www.ip.ndsoftware.net/
FNIX6 (French National Internet Exchange IPv6): http://www.fnix6.net/
EuroNOG: http://www.euronog.org/