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New Member

Need some 5509 switch Problem determination suggestions

Hello There,

I'm pretty new to switching and am having an issue I could use some problem determination guidance on.

Situation is this

I have a server connected to one of my 5509 switches that is getting a large number of single collisions and multi-collisions...several hundred a minute when there is traffic hitting the server.

Intially the NIC card in the server was set to 10 MB auto...while the 5509 was set to 10 MB half duplex.

In an attempt to get the collision rate down...we tried changing out all the patch cords between the switch and the nic in the server. This did not help.

Next we changed the NIC to go half-duplex...thereby matching 5509 figuring autonegotiation was causing the collisions

This did not help.

Next we swapped over to the 2nd NIC that was in the server...still keeping same patch cable and 5509 switch change...still getting many single and multi-collisions.

I'm considering my next move to be to set both the switch port and NIC to full duplex.....then maybe moving it to a different switch all together...although I have my doubts as to whether there is problem with the physical port on the 5509 .Is this a viable approach or is there something else to consider before that? I would appreciate suggestions. Thanks in advance

New Member

Re: Need some 5509 switch Problem determination suggestions

Just read Trobleshooting Ethernet Collisions from Cisco...According to them Single and Multicollisions are "normal" in a half-duplex setup like I have. Since I'm not seeing late-collisions I don't really have a problem per say...I would like some other opinions on this please. Setting both to "full-duplex" would get rid of the counter but what does it solve?



Re: Need some 5509 switch Problem determination suggestions

Full duplex eliminates collisons, not just the counter. Each collision represents delay. A lot of collisions indicate congestion; too many hosts trying to share a segment and stepping on each other's packets. Devices have to wait for the collsion to clear a resend data. In point to point scenarios; one host on a switched port, collsions can be eliminated if the hosts can go full duplex. I have not seen 10mb full duplex but it may be possible.

Cisco Employee

Re: Need some 5509 switch Problem determination suggestions

As you are using half-duplex, collisions are normal. In this case, as you see multiple collisions, it also looks like this segment is quite busy. Move to full-duplex if possible and 100Mbps.

New Member

Re: Need some 5509 switch Problem determination suggestions

I have trouble periodically with a few servers dropping the time we can ivestigate they are back and connected. I have moved one server to full-duplex (manually) on a 10 MB connection...not sure if it has helped or not. Users think it may be running a little faster....Just when I thought I had maybe seen the last of it..I had another occurance today with another server on the same switch dropping off...It is already running at a-full and a-100....If I have trouble at a-full and a-100 what else is there to try? Going to another switch? or replacing cards in multiple servers....that will be a hard sell!

New Member

Re: Need some 5509 switch Problem determination suggestions

Duplex problems can occur if one side is using auto-negotiation and the other is not. For servers and hosts which will not be moving around, set the switch port to 100Mbps and full duplex. You should configure the nic to operate this way as well.

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