cross connecting 3750 stacks

[fkatsumi1]

I'm new to Cisco switches.

I need to connect two 3750G stacks. One stack consists of 3 x 3750G-48PS and 2nd stack is 3 x 3750G-24TS. Since all switches have 4 SFP ports I would like to use them to create 3 3Gb etherchannels in a full mesh and redundancy.

stack1 Gi1/0/49 - stack2 Gi1/0/25

stack1 Gi1/0/50 - stack2 Gi2/0/25

stack1 Gi1/0/51 - stack2 Gi3/0/25

stack1 Gi2/0/49 - stack2 Gi1/0/26

stack1 Gi2/0/50 - stack2 Gi2/0/26

stack1 Gi2/0/51 - stack2 Gi3/0/26

stack1 Gi3/0/49 - stack2 Gi1/0/27

stack1 Gi3/0/50 - stack2 Gi2/0/27

stack1 Gi3/0/51 - stack2 Gi3/0/27

Is this overkill or am I headed in a right direction? I have only the default VLAN so I understand that only one etherchannel is used for cross stack connection. Will this achieve auto failover?

Fred

[Edison Ortiz]

Fred,

You are heading in a right direction and your configuration will achieve auto failover.

I don't think redundancy can ever be an overkill :)

[mmorris11]

Are these switch stacks physically close enough to connect with a stack cable?

[fkatsumi1]

they are about 100ft away and can't be stacked all together.

[glen.grant]

If you are using the stacking cables in the back of each of these stacks then it seems like major overkill on the connections between the boxes , hard to believe you would need that kind of bandwidth between the boxes but I don't know your traffic patterns . I would think 1 crosstack etherchannel ( 1 connection between each switch in the stack ) between the boxes would be enough .

[fkatsumi1]

Thanks for replying.

At first I was think to just create one etherchannel between the stacks but then I thought if we brought down the switch hosting it for any reason then there goes the connection. So I thought I should have 2 etherchannels but then I am thinking if I have 2 I might as well have 3 and fully mesh these stacks. Is this still overkill? Either way the bandwidth between the stacks will be capped at 3Gb. Is that such a huge bandwidth typically?

[glen.grant]

Not sure what you mean by "if we brought down the switch hosting it" , if you mean one switch in the stack then you would not lose your connection . The etherchannel would consist of one connection out of each switch in the stack on one etherchannel , the data would continue to flow over the other 2 links in the etherchannel. If you have one etherchannel consisting of one connection out out of each switch in the stack then you have 3 redundant gigbit connections , highly unlikely you would lose all 3 and this simplifies the config by only having one ehterchannel and saves money by not having to buy so many sfp gbics.

[fkatsumi1]

I thought I read that if I had two stacks A and B, I can only create a channel from one switch on stack A to 3 switches on B; and if I did a one-one connection it can't be combined into one channel. I would like make the interstack pipe larger than 1Gb.

Appreciate all your help.

[glen.grant]

We recently did it across a 2 switch stack to 2 other 3750's without a problem so I have no reason to believe a 3 switch stack wouldn't work , i am assuming though you are using the stacking cables in the back though . If you do this though you can not let the etherchannel dynamically create itself in crossstack etherchannel you have to force the channel on instead.