December 2020 - Bird-users

BGP with ECMP and weight control
by Alexander Demenshin 02 Dec '20

02 Dec '20

Hi, I have two uplinks (different AS), and one is more stable/preferred, but when "merge paths" is set to on, all routes are generated with weight 1: 5.21.41.0/24 proto bird nexthop via 10.16.0.1 dev uplink1 weight 1 nexthop via 10.17.0.1 dev uplink2 weight 1 Is there any way to adjust weight for ECMP generated from BGP sessions? I could not find any option/attribute when it is related to BGP or kernel protocol, while it is possible for OSPF and static protocols (to a degree). Adjusting local preference or med (in BGP) does not really help - weight is unchanged, though of course I could force routes from specific AS to be preferred, but then I lose ECMP and if preferred session is dropped it takes time to restore connectivity. Thank you! Best regards, Alexander.

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Direct routes and OSPF
by Alasdair Muckart 01 Dec '20

01 Dec '20

I've got a question about importing direct routes and interaction with BGP & OSPF. We have an issue with BIRD (1.6.3) when we do a 'configure soft' we end up with linknet routes being learned via indirect paths over OSPF which breaks BFD and BGP. It only happens with IPv6, not IPv4. Given routers A, B, C and D: A----B | | C----D Doing a 'birdc6 configure soft' on router A will sometimes end up with the linknet for A-C being put in the kernel table by OSPF learned from B. Not all interfaces are part of OSPF and I'm wondering if importing direct routes into BIRD for all interfaces would stop OSPF from trying to insert the routes into the kernel table? Any ideas would be greatly appreciated. Thanks. -- Alasdair Muckart (he/him) Network Engineer Catalyst IT - Expert Open Source Solutions Mobile: +64 22 638 5141 | DDI: +64 4 897 7794 | www.catalyst.net.nz CONFIDENTIALITY NOTICE: This email is intended for the named recipients only. It may contain privileged, confidential or copyright information. If you are not the named recipient, any use, reliance upon, disclosure or copying of this email or its attachments is unauthorised. If you have received this email in error, please reply via email or call +64 4 499 2267.

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ospf stub interfaces appears as two entries in routing table (direct + ospf)
by Kenth Eriksson 01 Dec '20

01 Dec '20

If I configure an OSPF interface as a stub interface, why does it appear twice the routing table? E.g. setting interface lo as stub interface results in the following; 10.210.137.78/32 unicast [direct1 15:59:09.550] * (255) dev lo unicast [ospfv2_1 20:47:56.864] I (145/0) [10.210.137.78] dev lo The source OSPF-I misleads me in thinking that it was learned from the OSPF area.

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