Testing a port configuration change

Unanswered Question
Jun 30th, 2010

Hi,

We have two stacked cisco catalyst3750s and each switch has a port which connects to our providers switches and all traffic is routed out through these ports.  Would I be correct in thinking that if one of these ports were to go down, as the switches are stacked the traffic would be routed though the other port?

The reason I ask this first question is because currently the switch ports are set to auto negotiate and I want hard set the speed and the duplex to match the providers ports.  So my second question would be if I hard set the port on switch1 would I be able to test this to see it worked before changing the port on switch2?  Initially I thought about using the ping x.x.x.x source fastEthernet command but it gave an error that an IP needed to be enabled on that port.  Is there any way of testing this connection is working?

Thanks

Matt

I have this problem too.
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John Blakley Wed, 06/30/2010 - 04:31

You should be able to source it from the vlan that it's connected to. Since they're stacked, the only real way to get an accurate test is to create some downtime and pull the other connection into the provider. How is routing done to this provider? Do they have a separate address for each connection into your switch, or do you only have one gateway to them. If it's the latter, the switch should route with no extra configuration.

How do you know that it's not going over the port now? If you're using a routing protocol, it's possible that you're load balancing the link.

HTH,

John

britcher85 Wed, 06/30/2010 - 06:04

Hi John,

Thanks for your quick reply

The one thing I was trying to avoid was downtime.  Both ports are on the same vlan which routes to a HSRP Address, so if I did make a configuration change on one port, would it be possible to check that port was still up and working before I made the change on the second port?

Thanks

Matt

John Blakley Wed, 06/30/2010 - 06:45

britcher85 wrote:

Hi John,

Thanks for your quick reply

The one thing I was trying to avoid was downtime.  Both ports are on the same vlan which routes to a HSRP Address, so if I did make a configuration change on one port, would it be possible to check that port was still up and working before I made the change on the second port?

Thanks

Matt

Matt,

What I would do is make the change to the port that's not active right now. I'm assuming that you mean both of these ports are configured with hsrp. What I would do is change the standby ports speed/duplex settings and make sure it negotiates. Then I would change the priority of that port to be higher than you current active and make sure you're preempting so the secondary will become the primary. Then I would change the "secondary" port settings and make sure those come up.

The problem that you have with testing to make sure traffic passes through this port is the way the switches are cabled. They're seen as one switch stack, and your vlan is going to be shared by those ports. So, unless you're using routed ports, you won't be able to test the ports individually like you're wanting to do.

John

britcher85 Wed, 06/30/2010 - 07:29

Hi John,

Thank you very much for you answer. I think your method sounds like the best option so far.  Fingers crossed for when we make the switch.

Thanks Again

Matt

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