PIX 515e ARP collisions

Posted on 2004-10-06
Last Modified: 2013-11-16
In my SYSLog I am seeing a lot of events:
%PIX-4-405001: Received ARP request collision from on interface inside
%PIX-4-405001: Received ARP request collision from on interface inside
%PIX-4-405001: Received ARP request collision from on interface inside
%PIX-4-405001: Received ARP request collision from on interface inside
%PIX-4-405001: Received ARP request collision from on interface inside
%PIX-4-405001: Received ARP request collision from on interface inside

--after looking at the packets I was able to determine that the MAC addresses are two servers using dual Nics (teamed for Load Balance). I have other servers with this same set up but I am not seeing events for those servers.

--According to Cisco: Explanation    The firewall received an ARP packet, and the MAC address in the packet differs from the ARP cache entry.
Recommended Action    This traffic might be legitimate, or it might indicate that an ARP poisoning attack is in progress. Check the source MAC address to determine where the packets are coming from and check to see if it belongs to a valid host.

Those MAC addresses are valid hosts. Is this a configuration issue or anything to be concerned with? Thanks in advance.

Question by:gl_3n2k3
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LVL 79

Accepted Solution

lrmoore earned 400 total points
ID: 12240493
What kind of switch are you connecting to?
If you have other server NIC teams configured the same, then I would investigate why this one is behaving differently. It could have a serious impact on the performance of that NIC team..


Author Comment

ID: 12242241
The server (both of them) are plugged into Dell 5224. The other NIC teamed servers are plugged into the same  switch, DELL 5224. The Core switch is Cisco 3550. I am only see those two servers logging this event.

After hours I am going to change one of them to a single nic to see if the events stop.

NIC configuration is nothing out of the ordinary. Static IP, Static DNS, WINs, etc.
LVL 12

Expert Comment

ID: 12243905
This is most likely caused by an incompatability between the NIC's and the switch that they are connected to in supporting the "teaming". If the Dell switch doesn't support PAgP, or doesn't support the same version as the software running the NIC's, you're going to have these kinds of issues. There may be little that you can do about it except change the switch they're connected to and possibly update your teaming software.
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Author Comment

ID: 12249884
I was able to resolve this issue. I removed the team on one server and the events stopped logging. I compared the drivers between servers not logging the event to the ones that do and found some minor revision version differences.  I updated the drivers for the NICs and Control suite on the server stilll using NIC teaming and the events stop being logged. I also cleared the routing tables of all gateway entries because there appeared to be a bad entry. I  For those of you that may be interested.

Broadcom NetXreme updated drivers for both NICs from Microsoft to Broadcom
BASP Virtual adapter updated from to
Control Suite updated from 6.03 to 7.6.7

The logs did not indicate any ARP collisions after this.

Thanks for the responses!

LVL 79

Expert Comment

ID: 12250211
Good work!
How do you want to handle closing of this Question?

Author Comment

ID: 12250755
I am giving you the points even though there wasnt an exact "fix" offered. I posted my fix in case someone else encounters a similar issue. Your comment to investigate the NICs lead to the eventually resolution. Thanks!!

I have another PIX log the is occuring with great frequency and was going to post it to see if any other's had experienced this (should I start a new post?). I havent started to troubleshoot it yet and may not even be an issue.

%PIX-2-106001: Inbound TCP connection denied from {external IP}/80 to flags PSH ACK  on interface outside 2004-10-05 15:44:59
%PIX-2-106001: Inbound TCP connection denied from {external IP}/80 to flags ACK  on interface outside

Per Cisco Error Event description:
Explanation   This is a connection-related message. This message occurs when an attempt to connect to an inside address is denied by your security policy. Possible TCP_flags values correspond to the flags in the TCP header that were present when the connection was denied. For example, a TCP packet arrived for which no connection state exists in the PIX Firewall, and it was dropped. The TCP_flags in this packet are FIN,ACK.

Action None required.

--- I dont think this is an issue but if its happening at great frequency then I may need to tweek some configurations.
LVL 79

Expert Comment

ID: 12252234
I don't think it's an issue. Whenever you open a web page and quickly click off to another link or something before the page fully loads, you'll see these type messages. You've closed the connection request to the initial page, but the graphics and things are still coming from the original request. They just get dropped...

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