Re: A router bug?

Meelis Roos (mroos@tartu.cyber.ee)
Sun, 31 Jan 1999 04:32:46 +0200

AC> If the MTU of the two links is different you should look for outgoing
AC> frames through the router with no reply when the size of reply would be
AC> large. Thats a clear indication that the remote site has firewalls set up
AC> by overpaid underbrained morons from one of the many rich and clueless
AC> consulting firms who think blocking all icmp on a firewall is a valid
AC> thing to do.

If by any chance he is running IP masq on that router, things may become
different. My experience shows that linux won't send back the ICMP error
message in this case (eth. MTU 1550, slip MTU smaller, big packet wants
to go through masq box but it never gets through and no ICMP message is
generated). But it should since it's the point where the MTU gets
smaller.

I tested it in 2.0.33 days, maybe things have changed. But somebody just
wrote about this in linux-kernel about a week ago ("possible bug in ip
masquerade" or something similar). 

-- 
Meelis Roos (mroos@tartu.cyber.ee)


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