[CentOS] CentOS 5.2 + iptables + memcached Problem

Sat Dec 13 15:14:24 UTC 2008
Filipe Brandenburger <filbranden at gmail.com>


On Fri, Dec 12, 2008 at 18:28, Art Age Software <artagesw at gmail.com> wrote:
> IPTABLES -A INPUT  -i bond0 -p tcp -m tcp  -s  -d
>  --dport 11211  -m state --state NEW  -j ACCEPT
> s1 kernel: DROP -- Catch All: IN=bond0 OUT= SRC=
> DST= LEN=52 TOS=0x00 PREC=0x00 TTL=64 ID=6467 DF PROTO=TCP
> SPT=51837 DPT=11211 WINDOW=202 RES=0x00 ACK FIN URGP=0

To use stateful rules, you must have rules for state ESTABLISHED too,
otherwise it will only allow the first packet and not the all others.
The first rule should always be:

iptables -A ... -i bond0 -m state --state ESTABLISHED,RELATED -j ACCEPT

That's the point of stateful rules, you match the rules further down
for new connections, but existing connections will always match the
first rule.

You should google for "iptables stateful" and try to get a better
explanation of what it is and how it works.