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JPenner
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MPLS - Labels dropping after outage

Mon Jun 01, 2020 7:52 pm

Our WISP network has been running OSPF/MPLS for quite a few years now, but we always seem to have issues with MPLS labels dropping between certain sites after a brief outage.

Today we had a power issue on one of our sites, and it caused the MPLS labels to not re-establish between a few of our sites in our network, including ones that were not the impacted site by the power outage.

This issue will be fixed by disabling and enabling the LDP interface on the affected sites that are dropping labels between them.

Any thoughts as to why this is?

Our tower site routers will have a /30 on a Vlan between them, advertised on Area backbone.
We have MPLS interfaces (dummy bridge) with an IP address on them that will also be advertised on OSPF.
Adding the Vlans as the LDP interfaces. - These are the interfaces we will need to disable/enable in order to get our labels back, along with the tunnels.

Another thing we have tried, is to add the MPLS interface to the LDP interfaces itself, and then statically adding the LDP neighbors (neighboring MPLS IP addresses), which works, but doesn't appear to fix this issue in particular.

Anyone else have issues with dropped labels on MPLS?
 
ste
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Re: MPLS - Labels dropping after outage

Mon Jun 01, 2020 10:02 pm

We also run into situations where we need to stop start LDP. E.g. with IP Changes on MPLS Interfaces and with new start of a router. Happens seldom so no big issue for us but it looks like there is a bug keeping labels up to date.
 
mducharme
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Re: MPLS - Labels dropping after outage

Tue Jun 02, 2020 12:06 am

We have this issue not caused by MPLS but by OSPF. Occasionally after an outage, we are missing some OSPF routes for loopbacks. Our VPLS tunnels are between loopbacks of course and so if we are missing a /32 route in either direction it doesn't come up. The OSPF route that is missing always appears precisely one half hour after the power is restored, at which point the VPLS tunnel comes back up by itself. If we disable and re-enable the OSPF instance or reboot the router it actually makes things worse, because then it ends up staying down until a half hour after we re-enabled the instance.
 
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nz_monkey
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Re: MPLS - Labels dropping after outage

Tue Jun 02, 2020 3:25 am

We have this issue not caused by MPLS but by OSPF. Occasionally after an outage, we are missing some OSPF routes for loopbacks. Our VPLS tunnels are between loopbacks of course and so if we are missing a /32 route in either direction it doesn't come up. The OSPF route that is missing always appears precisely one half hour after the power is restored, at which point the VPLS tunnel comes back up by itself. If we disable and re-enable the OSPF instance or reboot the router it actually makes things worse, because then it ends up staying down until a half hour after we re-enabled the instance.
I have experienced this multiple times. I logged a ticket with Mikrotik and got the usual "Fixed in v7" answer.
 
telcouk
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Re: MPLS - Labels dropping after outage

Tue Jun 02, 2020 1:45 pm

We have this issue not caused by MPLS but by OSPF. Occasionally after an outage, we are missing some OSPF routes for loopbacks. Our VPLS tunnels are between loopbacks of course and so if we are missing a /32 route in either direction it doesn't come up. The OSPF route that is missing always appears precisely one half hour after the power is restored, at which point the VPLS tunnel comes back up by itself. If we disable and re-enable the OSPF instance or reboot the router it actually makes things worse, because then it ends up staying down until a half hour after we re-enabled the instance.
I have experienced this multiple times. I logged a ticket with Mikrotik and got the usual "Fixed in v7" answer.
I reckon we're going to be bitterly disappointed when v7 is released, with the amount of promises being made.
 
mada3k
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Re: MPLS - Labels dropping after outage

Tue Jun 02, 2020 10:14 pm

Are you using any LDP accept/advertise filters?
 
mducharme
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Re: MPLS - Labels dropping after outage

Wed Jun 03, 2020 1:11 am

I have experienced this multiple times. I logged a ticket with Mikrotik and got the usual "Fixed in v7" answer.
OSPF is completely rewritten in v7 so I would be surprised if this bug still affects v7. There probably will be some all-new bugs to contend with, though (fun fun).

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