[nsp] ICMP type 3 code 4 + NAT (Was: ICMP: time exceeded (reassembly))

Jason Lixfeld jason at lixfeld.ca
Thu Feb 5 02:58:06 EST 2004

A question popped into my head while reading the earlier thread.

Assuming a web server is addressed via RFC1918 and accesses the 
internet via NAT.  Client is on some crummy link which requires a lower 
MTU than the web server, ICMP T3C4 message sent back to the web server 
(nat box).  How does the ICMP message get back to the web server from 
the NAT box?  Are there specific NAT hooks for these types of 
circumstances or are there special NAT provisions that need to be taken 
into consideration when running services like this behind a NAT box?  
(Assume NAT box is >= 12.0 IOS box).

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