10-21-2008 03:31 PM - edited 03-06-2019 02:04 AM
When, if ever, is it OK to use a ethernet cross over cable between two server clusters in a production environment? What are the benefits of using a switch?
10-22-2008 04:11 AM
If there's only communication between two hosts, no real advantage of a switch except perhaps as another way to capture traffic stats.
If you want to communicate between more than two hosts, something beyond a single cross over cable makes that a bit easier.
10-22-2008 09:17 AM
Thanks. That's how I feel. However, some people think that a switch somehow increases or propogates the electrical signal between the two boxes,, like a repeater. Thoughts? I think that adding a switch adds an additional and unecessary point of failure. Is there any industry best practice documentation that you could refer me to?
10-22-2008 10:04 AM
Actually switches do rebuild frames, so you can extend the distance beyond end hosts. But besides adding a point of failure, you also need to insure the switch can actually handle the offered traffic load and also note the switch will add some latency.
10-22-2008 02:32 PM
We had a server on a 3550-48 XL switch. The interface was rapidly accumulating thousands of underruns causing the cluster to fail over. We moved the connections to another 3550 and it still acumulated the underruns. So we put a cross over cable between the devices and the cluster stopped dropping frames and failing over. The cluster is performing well.
We had another server on a 3550 that was doing the same thing and we put it on a 4507 and it stopped. Where can I find information about the backplane fabric capacities for switches? Thanks for all of your help.
10-22-2008 02:42 PM
When you are having a problem with the overrruns use the "show controllers utilization " command and see if the port or switch fabric is being overwhelmed. Stats for the 3550 are here. For any switch just do a search on the main cisco page for
10-22-2008 03:51 PM
10-23-2008 10:49 AM
Thanks for everyone's help.
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