IPS 4255 in Inline mode is blocking internet traffic

[sunil.aroraa]

IPS 4255 6.0(4)E1 is installed in Inline mode(one interface Inline pair) between Nokia Checkpoint Firewall and Cisco router connected to ISP through Cisco Switch. In another Inline pair is connected to Intranet traffic and DMZ.

Interanet is working fine with same configuration(default config with VS0, rule0 and ad0 for both inline pair) but internet traffic is facing the problem. As soon as hits to specific web sites are increasing. Websites are not opening or working for some users whose session are already established.

Thanks in advance.

[smalkeric]

Check if thers is any duplex mismatch.

http://www.cisco.com/en/US/docs/security/ips/6.0/configuration/guide/cli/cliTS.html#wp1008674

[rhermes]

Check you Normalizer engine signatures. Some of them are set to drop without sending any kind of alert. See if you're getting hits on any of those set to drop packets. The external traffic might be different enough from your internal to trigger the signature(s).