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New Member

Etherchannel on 4000 sup II 's

Quick question? When I configure port 1/1-2 for etherchannel between 2 4000's is it a good idea to configure portfast enabled on those ports, or should I just keep portfast disabled??

Thanks in advance,

~zo

5 REPLIES
Cisco Employee

Re: Etherchannel on 4000 sup II 's

Portfast should be disabled on any link connecting to a hub/switch or a router

New Member

Re: Etherchannel on 4000 sup II 's

Why should portfast be disabled on a connection to/from a router? That connection should act just like a DTE device.

-Bo

New Member

Re: Etherchannel on 4000 sup II 's

Probably, because if spanning-tree is enabled it needs it's 15 to 30 seconds to converge and start forwarding to another path. You see if portfast is enabled on these ports and let's say that spanning-tree has a topology change then not enough time may pass between the blocking and forwarding states so theoretically you could have a loop. So that's why it is safe to turn port fast OFF when you connect a switch to switch / router connection. I think it's recommended to only use portfast on switch to workstation nics...

~zo

New Member

Re: Etherchannel on 4000 sup II 's

Your synopsis is true of switches, even layer 3 switches. However a router ,say a 2600 with an ethernet NIC, should be connected utilizing portfast so that your routing instance comes up more quickly.

-Bo

New Member

Re: Etherchannel on 4000 sup II 's

Error!!!

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