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Pix deny access to few sites (exemple :

hello every body,

We have a PIX 515E DMZ. On the DMZ interface there's a Linux Squid proxy cache.

The squid server is unable to connect to some sites like :, or etc ...

But the squid server can access the site

In other word some sites work, and some others don't work. I know that it is the PIX firewall who deny access to those site, because when I install the squid server directly on outside interface (internet) it work well.

I try to make some sniffing, I have noticed that the PIX sometimes send a ICMP message to the proxy cache server, which said "DF bit is set, fragmentation is needed).

On the PIX there is a rule which allow web access to any Web server.

thank you four your help


Re: Pix deny access to few sites (exemple :


Can you post some of the syslogs for me pls, either post here or to me at

logging on

logging buffer debug

sho logging



Re: Pix deny access to few sites (exemple :

Well, my first inclination here would be to take a look at your squid server and determine why it is sending packets to the PIX that are too big and have the DF bit set. Take a look and see if the MTU value on the interface has been changed to something smaller than 1500? I have a hard time believing that the Linix server would be sending ethernet packets bigger than 1500. But is some more information on the MTU commands on the PIX:


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