[squid-users] squid slowdown behind firewall

I am running a squid server behind a firewall.
Problem is the network slows down to a crawl. Including
web traffic and traffic within the network. The network
becomes ok when i remove the squid box from being inline.
I can surf the internet with the squid box, but it is so slow
that many pages timeout and clients get disconnected.

I cannot recompile the squid because it is embedded within
several other software. But i can reconfigure the operating system
and some squid.conf options.

my config
-----------
dual processor xeon 1.3ghz
primary hd = 40gb
other hd = 4 x 120 gb
3com nic = 2 x 10/100mbps
linux redhat 6.
sonicwall firewall (i am not familiar with this product)
200+ users only
transparent proxy
bridging enabled.
services enabled , ssh, snmp, httpd, CacheXpress (propriety)

I am not familiar with squid so this question may be very broad. Biggest
problem i have is that i cannot re-compile the kernal without breaking
the other services running.

i am hoping someone has experience with squid behind the sonicwall firewall
will respond with some configs for the OS.

Andrew

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