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Cannot download from Internet through FWSM

roger perkin

I am running a pair of 6509's with 720 Supervisors and a pair of FWSM's in Active/Standby

In the last two weeks we have been unable to download successfully any files from the internet larger than about 5Mb

Web browsing is fine.

If I connect my laptop outside of the FWSM downloads work fine.

This is not affecting normal service and we are hosting many servers behind the FWSM without an issue.

But these servers are unable to download updates from the internet.

If we point to a proxy (Websense) which sits outside of the FWSM downloads work fine.

I have failed over the firewalls and rebooted both without any progress.

I have also tried the sysopt np completion-unit command without any success.

If I run a packet capture I am seeing a lot of out of order packets and TCP retransmissions, but this is also the same for a capture outside of the FWSM

I have a call running with TAC but just wondered if anyone has seen this kind of issue before, as it is becoming very difficult to poinpoint the cause.





7 Replies 7


I had this issue once on a 2800 router acting as their firewall. The firewall is having trouble dealing with an excessive amount of fragmented packets. We tried upgrading, but it did not help. ISP said it was not on their side, but eventually the customer saw their truck down at the corner working on something, after that there were no more fragmented packets and no more downloading issues. So I would have a call with your ISP as well, unless you can download large files internally.