I had a similar issue with my firewall in the past couple of weeks.

The base issue *looked* like DNS problems, and they were, sorta...

We found that the real issue was a state table on the firewall,
limiting UDP sessions. It was set at a max of 2500, and when I looked
at the table, it was sitting at 2499 or 2500 for extended periods of
time. So, I doubled the limit, monitored it for a while, then found it
was hovering between 4500 and 5000 quite a bit, so doubled it again to
10000.

The timeout for sessions was also set to 300 seconds, and I turned
that down to 60 seconds.

Those actions cleared my problem - don't know if it's the same issue
for you, but it might be worth looking at.

On Fri, May 27, 2011 at 09:34, Level 5 Lists <[email protected]> wrote:
> I have a client with a t1 and cable as a backup for about 50 users and 9
> servers.
>
>
>
> The past week their internet became amazingly slow, we pulled opendns out,
> we pulled the proxy filter out and still same thing.
>
>
>
> Reviewing onsite it seems like when we goto a webpage we get a lot of
> website found waiting for reply for several seconds.
>
>
>
> I switched gateways between t1 and cable and seemed to have no effect. You
> eventually get there, but I cant seem to pinpoint whats causing it.
>
>
>
> We tried removing the opendns forwarders, then no forwarders, then some
> forwarders to some public DNS servers. Always the same thing.
>
>
>
> Internally dns seems fine, no errors, ad replication is functioning okay etc
> etc .. Kind of at a loss as to where to look next.
>
>
>
> Speedtest/pingtest are showing speeds as expected on both connections,
> latency everything there seems pretty normal (16dn/6up on cable, A rating on
> pingtest)
>
>
>
>
>
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