Subject: R: Re: mtu issue with ipsec tunnel and netfilter snat

From: "[email-masked]" <[email-masked]>
Date: Thu, 10 Jan 2013 17:46:57 +0100 (CET)

[email-masked] wrote:
>On Wednesday 2013-01-09 10:01, [email-masked] wrote:
>
>>As you can see there are incoming 1500 bytes packets (these are the
>>decrypted ipsec packets) with DF bit set. These packets are never
>>delivered to the final client 10.81.128.176 (the destination address
>>is 172.16.128.1 which is the ip used for SNATing the original ip
>>10.81.128.176).
>>
>>IMHO this is a mtu issue: 1500 bytes packets cannot be routed inside
>>the ipsec tunnel.
>>
>>But why linux_gw_snat is not sending icmp need to frag packets to
>>10.148.12.23?
>
>Perhaps because ICMP was blocked erroneously?

well, I don't see the icmp packets
because tcpdump 'see' only the incoming
ipsec clear packets. Is there a way to
see the outgoing clear ipsec packets
with tcpdump?