ELRP uplink port question

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We are running ELRP on all our ports. including the 10gig ports; that we use for our backbone. on stacks with the 460 48 port switches. We had a loop created when two switches were connected via 1gig ports ( ex stack 1 port 12 to stack 2 port 8). As expected elrp shut down those two ports and the backbone ports(ex 1:53 ) on both switches. We were considering taking the elrp off the backbone ports so it we wouldn't lose connection to the switch when this type of loop happens.

my question is with elrp no active on the backbone ports. will elrp still recognize the loop( since it is not monitoring the backbone) and if it does see the loop. It will still shutdown the 1 gig port only.

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christopher madison

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Posted 3 years ago

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Bill Stritzinger, Alum

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In your design, it would be best practice to not have ELRP on the uplinks and just on the edge ports.  There is a new feature in 16.1 where you can define the port that will be disabled, either the ingress or egress port.  This would allow you to make sure uplink does not get disabled.  My suggestion is to not have the uplinks participate. Here is the new command line options....

configure elrp-client periodic <vlan> ports <{portlist} |

all> {interval <seconds>} [log |log-and-trap | trap]

{disable-port {egress | ingress} {duration {<seconds>} |


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Kawawa, GTAC

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If you disable ELRP, it won't see or do anything.  But you can change what action it takes when it identifies a loop.  With the commands Bill has highlighted above, you can simply set it to Log/Log & Trap/ Trap, allowing you to be notified.  Most production environments I have worked with simply have it set to log/trap the loops and the network team then remotes takes the best corrective action based on the circumstances
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Patrick Voss, Alum

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You can keep the same configuration and just exclude the uplink ports from being disabled if there is a loop. This is explained in the article below:

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Grosjean, Stephane, Employee

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Hi Christopher,

In my understanding this statement:

"As expected elrp shut down those two ports and the backbone ports(ex 1:53 ) on both switches."

Is not expected.
It should shut down one port. If you don't have the uplinks in the exclude list, they might be the one shut down. Actually, by default, the port being shut down is the receiving port where the ELRP PDU is received. This can be change by configuration starting with 16.1, as Bill stated.