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Cisco FWSM Denying Outbound ICMP (type 3)

Posted on 2009-05-05
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Last Modified: 2012-05-06
I have a Cisco firewall that is logging the following SYSLOG (about 15 per second):

Denied ICMP type=3, from laddr 10.1.72.30 on interface Inside539 to 67.128.185.202: no matching session

The destination IP of 67.128.185.202 varies, but the source is always the same.  I have found that the customer has SolarWinds installed on this host.  Why would the firewall be blocking OUTBOUND packets when I have an outbound ACL (applied to Inside539 interface)?

access-list Inside539_access_in extended permit ip 10.1.72.0 255.255.255.0 any
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Question by:Venyu
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harbor235 earned 500 total points
ID: 24314364


is someone scanning from inside your network outbound? Aah solarwinds, someone is scanning

ICMP type 3 is destination unreachable, do you have a default route outbound, can you route to 67.128.185.202 (try pinging from the same subnet) 15 per second is a pretty good rate.

The firewall will approximate icmp connections, if the icmp message does not have a nmatching component you can get this message, i am not sure how someone generates the type 3 unsolicitated unless they have a packet generator.

Coupls of things, sniff the traffic coming from the suspected port and see ehats coming in and going out

harbor235 ;}
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