internal host can not access hotmail

Wenzhuo Zhang wenzhuo at zhmail.com
Tue Feb 22 03:55:27 CET 2005


Yuwen Dai wrote:
> Any advice to diagnose this problem?  I once thought maybe something
> wrong with the FORWARD rules, and tried to log the blocked
> packages. But there's no log info.

Probably you're encoutering the Path MTU Discovery problem. There are 
serveral solutions to this problem.

1. Lower the MTU of the network interface of your internal host.

2. Use the clamp-mss-to-pmtu feature of iptables:
    # iptables -I FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS \
         --clamp-mss-to-pmtu

3. Use the clamp MSS feature of rp-pppoe (e.g. -m 1412).

Wenzhuo
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