a few etherchannel questions

[rhltechie]

Hi All,

I am finally getting to replace our Dell POS switches. I am going to run VTP as well as etherchannel between a few floors. I have a few questions about etherchannel.

I will be running between a core 4507r and 3750 switches. i will stack 5 3750's on one floor and two on another.

my question, as i understand it you can run etherchannel from each switch in the stack to create a cross stack etherchannel correct? so in theory i could run an etherchannel on each switch in case one goes down? also, will all of these ports be in the same logical etherchannel? can i run trunking on these channels? being that i am doing cross channel i cannot run PAgP right? are there any issues with doing this between the 4507? also, is the "on" mode what most people use when they cannot use PAgP?

the 3750 config says these ports can be L3 ports so that I can assign an ip, how does this work if they are trunked ports? (isnt trunking L2?)

also, as a side note, it is best practice to keep all switches in a vlan together and off of the same vlan with users correct?

TIA,

R

[Roberto Salazar]

my question, as i understand it you can run etherchannel from each switch in the stack to create a cross stack etherchannel correct?

YES.

so in theory i could run an etherchannel on each switch in case one goes down? also, will all of these ports be in the same logical etherchannel?

YES, but no more than 12 EtherChannels cannot be configured on a Catalyst 3750 switch stack.

can i run trunking on these channels?

YES.

being that i am doing cross channel i cannot run PAgP right?

cross-stack etherchannle using LACP or PAGP is not supported.

are there any issues with doing this between the 4507?

No, it's like channeling between 3750 and any otehr switch.

also, is the "on" mode what most people use when they cannot use PAgP?

Yes, since you cannot use negotiation to channel, your only option would be to turn it "ON".

the 3750 config says these ports can be L3 ports so that I can assign an ip, how does this work if they are trunked ports? (isnt trunking L2?)

Then you create an SVI for the trunked vlans. If they are L3 then you cannot trunk, right? You will say what about sub-interface? then why not channel at L2 and trunk that channel and create SVI?

I hope this answers your question.

[rhltechie]

Thanks for your reply. So for the last question and answer, you are saying to make the channel a L2 trunk and then just add an ip to say the mgmt vlan int on the switches?

[Roberto Salazar]

If all the switch is going to do is L2 then yes. If the 3750 will be default gateway for the users vlan as well then you also need SVI for those vlan, right?

[rhltechie]

its only going to do L2, correct. My default gateway will be the core 4507. is this not best practice?

[Roberto Salazar · Accepted solution]

Yes, this set-up is fine.