3750 stacking question, etherchannel question also

borumas

Hey guys, was wondering about this, I am stacking 4 3750 switches and I start by configuring them out of the stack alone and the top one gets configured and stays as switch 1, then I make the next one switch 2, next switch 3, next switch 4. I then boot up switch 1 first and then the others, I'm consoled into switch 1, then use the range command to set the other switch's ports to match switch 1's and save it- is this an ok way to do this, or should I configure each one individually and then stack them so they all have the same port settings saved to them individually or is that done automatically when consoled into switch 1 and I do it?
Also I haven't used port channeling but I setup a 3712 gig fiber switch so that port 7-8 are on a channel and group, channel 9-10 are on a group, etc.., should the switch I attach those to match the group # or is that just pertaining to the local switch. For example if on one 3712 ports 7-8 are on group 3 and attached to ports 7-8 on another 3712 that is on group 1 will it make any difference?
I'm sort of learning on the job with this stacking business so thanks for any input.

he-man

Hey borumus,

Not sure on the stacking question, but as for the etherchannel, i'm pretty sure the channel is local, because if you think about it, if you had say 3 switchs, A,B,C..... A would link to B on channel1 and vice versa but B would have to link to switch C on channel 2 and then C would link to B on its channel 1 or 2.

But this may only apply to 3 switchs that arn't in a stack?

Hope that makes sense!

Spudage

The numbering for the LAG has only local significance. It does not need to match at each end of the link.

Rearden

We have a stack of two 3750s here feeding one of the campus academic buildings. When we installed them, we stacked them first, and then configured it. At that point, it didn't matter how you did things because together they act as one switch. So, I would think that a copy run start copies the configuration file to both switches. For example, there is only one IP for the switches to telnet into them.

Hope this helps,
Matt

borumas

Thanks guys, I think things will be fine but just wanted to double check, will be doing a major changeover tomorrow on a network and didn't want any "surprises" to pop up.

ignign0kt

Could someone point me to some info on stacking? I've never even heard of it. I don't think it's part of the CCNA curriculum.

borumas

On the 3750's there are 2 ports on the back that allow a 32gig backbone across the stacked switches, I believe you can stack up to 15 devices with them (could be wrong though). You can assign switch #'s to it or allow it to automatically assign them and upon booting up a master switch is elected and it controls the others. Upon booting a stack the switches appear in the config just like the modules do in a 6500 or 4500, in that they are listed together. Here's a few links:
http://www.cisilion.com/cisco-3750.htm
http://www.networkworld.com/reviews/2003/0811revcisco.html

Pash

Rearden wrote:

We have a stack of two 3750s here feeding one of the campus academic buildings. When we installed them, we stacked them first, and then configured it. At that point, it didn't matter how you did things because together they act as one switch. So, I would think that a copy run start copies the configuration file to both switches. For example, there is only one IP for the switches to telnet into them.

Hope this helps,
Matt

You can set different managment IP's for the stack though. In a vlan environment for example.

The mis-conception here is that although physically and logically they are forced to be one switch, they can still be differentiated even with the show version command. However, Im fairly sure no matter which IP you use to connect to the stack, the master is counted as the "main" switch and the other switches are labeled switch 0# after that.

Good link here:

http://www.cisco.com/en/US/products/hw/switches/ps700/products_tech_note09186a008010e9ca.shtml

Edit: Scrap the Im fairly sure answer, i just telnetted into a live switch environment with two 3750's stacked and I can confirm that not matter which IP you use to telnet into the switch the master is always displayed as the main switch seemingly.

mgeorge

Stacking is actually becomming a large part of the campus networks in the world today.

Most of the new networks I've worked with use 2x 3750G-16TD with 1x10Gig port, those
are stacked to preform the distro layer, and 2 or more 3750-48PS are stacked to form
the access layer.

A 10Gig backbone is becomming a reality in alot of companies.

Here lately I've seen some REALLY NICE networks.

Rearden

We use 3750s for distribution and 3560s mostly on the edge. They're really fun to play with

Interestingly, there were (and still are) a lot of 3com stacks out there, which behave differently than a Cisco stack. 3Com stacks see the switches as separate to the point where you often have to switch to another unit to configure that particular unit. Mostly, it's just a way to allow a few switches to share a fiber connection to the core network.