Switching

Hello,

please excuse beginner questions.

We have two distant EX4200 connected via 10G uplink module. The 10G interfaces are IP interfaces.

Now we managed to get another link, from other operator, and we would like to use it as backup link between these two Junipers. But in a way, that only one at a time would be active. And in case of link failure, it would switch to other link.

xe0 ----main link---- xe0
xe1 ----backup link---- xe1

If we use RSTP, we would have to manually change IP address from xe-0/1/0 to xe-0/1/1

If we use LACP, it will use both links and load balance the traffig among them. One of our customers sends 1G of multicast transport stream over this Junipers and he says, that load balancing causes them big troubles with jitter or what.

Can we somehow combine RSTP and LACP? So both 10G interfaces would act like one interface with one IP address and always only one active link?

Or can we somehow configure LACP, so it will not do load balancing and use only one link at a time?

And one more question: When the link from our operator fails, it usually does not turn off. It usually stays active. Is this problem with RSTP or LACP? I mean, will it recognize that the link failed, even if the port doesn't turn off?

Thank you for your patiance with me

You can configure the interfaces in identical way and allow only one VLAN for which you will configure a RVI on both sides of the link. This RVI will be your L3 link between the two devices.

Then xSTP will choose the best path and keep the other one as backup. You can alter the defaults to make sure that the link you want to be primary becomes actually the primary link.

xSTP will take care of the primary/backup switching. But there will be a short service impact until BPDU expires.

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Thank you,

but I don't know if it is applicable for our case...

The "xe" interfaces that interconnects the switches are configured like this:

xe-0/1/0 {
    mtu 9216;
    unit 0 {
        family inet {
            address x.x.x.x/30;
        }
        family mpls;
    }
}

 We are running some MPLS/CCC tunnels over it. I am afraid that MPLS is not supported on RVI (Junos v. 10.0R2.10)

Then why you don't use a /30 on the second link and manipulate the IGP metric so the new link will not be used unless the primary will go down? In this way, the LSPs will use the primary link until it will go down.

=====

If this worked for you please flag my post as an "Accepted Solution" so others can benefit. A kudo would be cool if you think I earned it.

I agree that using a second /30 network for the new link with a higher metric in the routing-protocol is the way to go here.  If you wanted to get really fancy, you could likely use a second routing-instance with the reverse preferences to have some traffic default to using one link, and other traffic defaulting to use the other link, but with both paths converging in the case of a link failure.  I would also recommend you try using the BFD protocol for establishing protocol adjacency (whatever your IGP of choice is) since carrier circuits can definitely be "down" without you detecting a loss of link.

Ron