[Snort-users] non-standard-protocol : BAD-TRAFFIC IP Proto 103 PIM

David Ryan David.Ryan at ...13912...
Thu May 17 07:21:56 EDT 2007

Hi all,

I am seeing loads (like 90% of all events) of these events showing up on one of my Snort sensors.  I have looked at the description here - http://www.snort.org/pub-bin/sigs.cgi?sid=2189 - and I looked at the rule definition and it appears to match simply on the existence of IP protocol 103 as distinct from any payload within it.

I see the traffic coming from two known Cisco routers on the subnet I'm monitoring and the traffic is destined for which is the multicast address for PIM - http://www.networksorcery.com/enp/protocol/pim.htm  I have also I have seen it on other sites and subnets on the network I am monitoring, so I guess whatever function is causing this traffic to originate from the router is used across the organisation.

In order to make the output from snort a little more readable (and because it is matching on the protocol and not the payload) I have disabled this rule.  I know the protocol in question is a routing-related protocol, but does anyone have any views or explanation on the normal use of this protocol ?


David Ryan
IT Security Engineer, Global IT Security
Quintiles, Global IT - Infrastructure, QDUB

david.ryan at ...14057...
v:  +353-1-819-5186, GMT+0
m: +353-87-124-9108

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