FRR shows duplicated OSPF routes (duplicate nexthop removed) #17869
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edvinaskairys
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It looks like FRR is installing OSPF External Type 1 metric ECMP routes via the same next-hop. |
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These are in fact different OSPF ASE paths and they should be displayed in the OSPF route table. If you use the "detail" keyword on "show ip ospf route", you'll see the paths correspond to different advertising routers. We will discuss whether it is worth preventing these from being sent to zebra. |
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Hey, thanks. Its quite interesting, because we're having very old FRR version server running at the same site, and it shows the same external routes: (it has two nexthops, because two different interfaces available via ECMP - working as expected) Meanwhile on FRR 10.2.1 As i understand some underlying FRR OSPF mechanism understands that other routes are duplicated and because of that, they are installed into RIB and this is just cosmetic problem ? |
From the next-hop addresses and interfaces, these are OSPF route tables for different topologies. So, it probably has nothing to do with the FRR version. If you run the older version on the first topology, I'd expect you'd get the same outcome. |
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actually its the same topology, server with the old FRR version are just sitting on different p2p links, but the same OSPF area. i dont know if it helps, but for example here is the output for external LSA for 10.1.0.0 link old frr version: New FRR: |
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Description
Installed FRR 10.2.1 on Rocky Linux 9.5, interfaces are configured with network manager. When running the ospfd, 3 of 4 ospf external routes is shown as duplicated.
Don't know if it helps, but i'm using multiple ospf instances: ospfd_instances="1,2" configured in /etc/frr/daemons.
Lets take the same route and see:
Its strange that only one interface is available
eno12409.208, butshow ip routeshows all 4 routes, even only one is correct. Is this correct behaviour ?ip routeon Linux shows as correct and expected.Version
How to reproduce
Configure ospf neighbourship between Rocky Linux 9.5 and FRR. Look at ospf external routes.
Expected behavior
FRR should not(?) consider all external routes as duplicated ?
Actual behavior
FRR considers external routes as duplicated
Additional context
No response
Checklist
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