UDLD and Loop guard

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Nov 4th, 2007
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Cisco Recommends to enable UDLD on etherchannel and Loop Guard on Non designated ports(Root and backup) . if there are 2 core with STP loadBalancing so the EtherChannel will be No-designated for some vlans So my questions is that Can i enable both of UDLD and Loop Guard on the etherchannel ports?

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bvsnarayana03 Sun, 11/04/2007 - 21:03
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UDLD & loopguard are the methods of preventing abnormal conditions in stp due to unidirectional communication. When udld is enabled on interface, it sends udld pkts & waits for the response from connectd neighbor. If its not recvd, udld considers the interface as unidirectional & shutdown.

Manual intervention required to make the port operational.

Loopguard on the other hand, puts the port in loop-inconsistent state in case of unidirectional condition i.e. when bpdus are sent but not recvd. When the port starts recving the bpdus, again stp calculation is run & port is transitioned to a suitable state. no manual intervention required. Loopguard only aplies to active vlan instances on the port.

Hope that clarifies, which option is better.

welcomeccie Mon, 11/05/2007 - 02:09
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Core1 ---Etherchannel----Cor2

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Thank you for your reply .But can i apply both of the UDLD and Loop guard on the etherchannel?

bvsnarayana03 Mon, 11/05/2007 - 02:59
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my thought is to have loopguard, as there is no manual intervention required.

welcomeccie Mon, 11/05/2007 - 03:54
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But cisco Recommends to use UDLD in etherchannel and use desirable mode too so can i apply loop guard too with UDLD

I appreciate your reply


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