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New Member

FE ports watching FE ports


I have 2 MetroE circuits connecting to Service Provider's L2 MPLS. How can i configure FE port to watch FE port such that when FE0/0 is down, the FE0/1 will be up?

Hall of Fame Super Silver

Re: FE ports watching FE ports

Hello Leow,

you can use the backup interface command or you can rely on STP. (if your device is a switch)

int f0/0

backup interface f0/1

f0/1 will be reserved for usage when f0/0 is down it cannot be used for other purposes


Hope to help


New Member

Re: FE ports watching FE ports

Just to add and make search for original poster easier, the feature with backup interface in switches called Flex Links.

New Member

Re: FE ports watching FE ports

Thanks! but MetroE typically will show interface as up even if the remote end is down. How do i go abt this? I can only use 1 set of /30 IP for WAN.

Hall of Fame Super Silver

Re: FE ports watching FE ports

Hello Leow,

to provide a better help some information is needed: what type of platform are you connecting to the MetroE service?

You have spoken of interface fas0/0 and fas0/1 so my guess is that this is a router.

Another important aspect is there is any STP information carried over the links and who is the possible STP partner (the local provider switch or your remote site) for your device.

However, if you get a layer2 service over the metro ethernet you should be free to use a second /30 private ip address (RFC 1918) over the second link and you can use a routing protocol to detect when the primary link fails

This is probably the best way to deal with your two metroethernet links.

To use both with a single /30 you could:

a) make a port-channel but requires cooperation of provider and if the two links are terminated on a different SP node this is not feasible


b) use integrated routing and bridging (IRB) but this requires that the service is able and willing to transport BPDU frames over the two links between your two remote ends. However the root bridge side cannot detect the failure of the remote end

So I think using a second /30 private ip address is the best solution and gives you the capability to detect when the links are up and operational on both ends

the following document design for enterprise and metro ethernet may help

in metro ethernet concepts like ethernet lmi have been introduced that could help to detect a remote failure like it happens in FR or ATM.

You can ask to your MetroE provider about these options if they are available or not.

If this option is available and the local interface could reflect the state of the remote end this would make the backup solution again viable.

Hope to help


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