Hello,

I am trying to install Zimbra Free edition on ESX hosted Linux but I found a strange problem with big MTU size.
Zimbra is installing correctly but I see the following packets when I try to access it:
Code:
22:05:11.442098 IP (tos 0x0, ttl 64, id 18170, offset 0, flags [DF], proto TCP (6), length 2760) A.A.A.A.7071 > B.B.B.B.47842: . 14007:16727(2720) ack 1190 win 7956
22:05:11.442117 IP (tos 0xc0, ttl 64, id 29278, offset 0, flags [none], proto ICMP (1), length 576) А1.А1.А1.А1> A.A.A.A: ICMP B.B.B.B unreachable - need to frag (mtu 1500), length 556
        IP (tos 0x0, ttl 64, id 18170, offset 0, flags [DF], proto TCP (6), length 2760) A.A.A.A.7071 > B.B.B.B.47842: . 14007:16727(2720) ack 1190 win 7956[|icmp] 

22:05:11.880925 IP (tos 0x0, ttl 64, id 18175, offset 0, flags [DF], proto TCP (6), length 4120) A.A.A.A.7071 > B.B.B.B.47842: . 18087:22167(4080) ack 1190 win 7956
Legend:
A.A.A.A - Zimbra IP
A1.A1.A1.A1 - Zimbra gateway IP
B.B.B.B - my PC IP

These lines are from tcpdump when I am trying to access Zimbra server. The strange thing is that Zimbra responds with bigger MTU than its physical interface supports (in red, my MTU is 1500). I tried to install zimbra on Debian4, Debian5, Ubuntu6, Ubuntu8, Fedora 11 and I have the same problem. However I installed Zimbra on VMware Server with Fedora 11 and it works. So probably there is a problem only with ESX, I use ESX4 update1 on Nehalem architecture and version 7 of virtual hardware.

If anyone have ideas ...