Hi,
I have a curious problem.
My box (linux) is trying to send mail to a target.
Between my box and the target there is a linux box 2.2.12
with 4 NICs but (for now) _without_ any filtering rules
at all (all default to ACCEPT).
Only 2 NICs are up: eth0 to external net and eth1 to internal net.
The problem is that when I tcpdump the 2 NICs from this middle-box,
I can see a SYN getting out from eth1 and then passed to eth0
(ip forwarding is enabled), and then I receive a SYN/ACK from the
target box via eth0, but this SYN/ACK _never_ reach
eth1 (which point to internal net) !!!
Why ?
Am I missing something ?
___________________
|
|
| <- SYN
|<- SYN <- SYN |
|
Target |
|eth0 eth1 |----------|
My box
| SYN/ACK -> | ->
| | telnet target
25
|_____________ ____|
^
|
|_____ SYN/ACK never reach eth1 :-(
Also when I telnet target 80 from My Box, it works !?!
kernel 2.2.12,
/proc/sys/net/ipv4/conf/{all,eth*}/rp_filter are set to 1
/proc/sys/net/ipv4/ip_forward
is set to 1
Thanks in advance,
-- Meir
