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Author Topic: lacp key port 1-48  (Read 3141 times)

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Offline jeff2679

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lacp key port 1-48
« on: September 08, 2014, 04:31:46 PM »
Hi all,

if you are terminating 4-10 Nortel edge switches on a Cisco 4500X Core Switch do you need to configure different lacp keys on the Nortel edge switches  or the default will work just fine on each edge switches ?.

Also if the lacp timeout-time port 1-48 long is set to long instead of short what is the implication if any ?

And lastly, do I need to worry about  STP configuration ? below is what I have configured.

spanning-tree bpdu-filtering port 1/47-48 timeout 120

Thanks


Offline Telair

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Re: lacp key port 1-48
« Reply #1 on: September 08, 2014, 06:45:27 PM »
I suppose there should be no problems if all the Nortel switches reuse all the same LACP keys as long as the Cisco has each Nortel switch as a separate LAG group.  LACP doesn't care what keys the far side of the link uses, just what it uses on it's side.  So you could use, say 13 as a key value on all the Nortel switch as long as the Cisco uses different keys for the respective switch LAG's.

Long timeouts mean a port will be removed from the LACP group if it misses 3 packets x 30 seconds per packet.  So it takes 90 seconds to detect and remove a downed link.  Short timeouts means if a LACP port misses 3 packets x 1 second per packet is 3 seconds to detect a bad link.  So short is much faster, but it is not the default value.  I have found that unless you know both ends of the link support short timeouts, stay with the standard long values.

Typically you don't run spanning tree across aggregated ports since they can't loop.  But it can cause a spanning tree reconvergence calculation if ports start dropping ports from LAG's.  So it's better not to use STP on aggregated ports unless you are really sure you want to.
« Last Edit: September 08, 2014, 06:48:58 PM by Telair »

Offline jeff2679

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Re: lacp key port 1-48
« Reply #2 on: September 08, 2014, 07:03:10 PM »
Thanks Telair for the concise explanation do i disable STP using the command below:

spanning-tree port 47-48 learning disable
 
Thanks

Offline Telair

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Re: lacp key port 1-48
« Reply #3 on: September 08, 2014, 07:08:31 PM »
Yeah, that should do it and disable spanning tree on ports 47-48.

Offline jeff2679

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Re: lacp key port 1-48
« Reply #4 on: September 08, 2014, 07:13:52 PM »
Thanks Telair

This is the last question, i promise. The below command is very confusing. The second line sets STP bpdu filtering timeout to 120 sec and the following line says no stp bpdu filtering on the defined port. Please break it down for me.

interface FastEthernet ALL
spanning-tree bpdu-filtering port 1-48 timeout 120
no spanning-tree bpdu-filtering port 1-48 enable
exit

Offline Telair

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Re: lacp key port 1-48
« Reply #5 on: September 09, 2014, 05:10:38 PM »
You should be able to do all your BPDU commands in one line.

spanning-tree bpdu-filtering [port <portlist>] [enable] [timeout <10-65535 | 0> ]

A 0 timeout value means stay down forever if you recieve a BPDU packet.  So your command should be:

spanning-tree bpdu-filtering port 1-48 enable timeout 120

I would also recommend the use of "spanning-tree bpdu-filtering ignore-self" to prevent the switch from disabling a port due to BPDU looping if an IP phone reboots or is powered off while still connected to the network.