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New Member

Is this normal?

Hi,

My PIX 515e is showing the following message in the PDM log:

Deny icmp src outside: (ip address) dst inside: (ip address) (type 8, code 0) by access-group 101.

Is this normal or should I be worried?

Thanks for any replies.

Robin.

4 REPLIES
Gold

Re: Is this normal?

Robin,

I see allot of these icmp deny messages, basically someone out there is sending icmp traffic on to your inside ip address - to state the obvious - but you firewall is doing exactly what it was configured to do i.e. STOP icmp sweeps etc. Is all of the icmp source address the same? If so then you can look up one of these addresses by going to www.whois.org and use the whois resources section to ascertain the owner/ISP of the ip address.

I doubt that all the source addresses are the same; unfortunately in this case you'll find it hard to track down the originator!! But as I mentioned before your PIX is doing its job correctly and denying all icmp traffic.

I wouldn't worry too much about these icmp traffic. One thing you can also do is to go to www.grc.com and use shields up service to check if there are any 'holes' on your firewall, this service I've used many times and it's secure and free.

Hope this helps and let me know if you need any further assistance.

Thanks - Jay.

New Member

Re: Is this normal?

Many thanks for your reply Jay.

At least I know my firewall is doing what it should!!

I have tried a few of the IP addresses in whois and a lot of them are coming from Australia!!

I am tring to contact the ISP for these domains but do not hold out much hope of any response.

Thanks again for your help.

Robin.

New Member

Re: Is this normal?

Quick followup question--

11-14-2003 19:14:55 Local5.Error 10.42.1.1 Nov 14 2003 13:17:02: %PIX-3-106011: Deny inbound (No xlate) icmp src inside:10.41.52.99 dst inside:10.38.127.6 (type 8, code 0)

10.41.52.99 is a valid network/host on my network. 10.38.127.6 does not live on my network anywhere.

I'm assuming that its an outside address on the Internet somewhere, but how can that be the case ?

Thanks--

Cisco Employee

Re: Is this normal?

This is how the PIX is seeing this packet. Somehow this host at 10.41.52.99 tried to icmp to 10.38.127.6 address. since it is not falling in the same subnet range as of source host, the packet will come to pix and get discarded there.

Just a thought.

Thanks

Nadeem

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