On 5/15/24 22:00, Hendrik Visage via zanog-discuss wrote:
Anybody else being as masochistic as I am to attempt using FRR's IS-IS with unnumbered interfaces? It works "like a charm" with IPv6, but IPv4 isn't routed if no IPv4 IPs on the IS-IS connected interfaces. Using Openfabric (based on and in the isisd code), it all just works... correctly (So why am I not using Openfabric? as I want to use it with multi node links/networks which Openfabric doesn't support/do, and I'm interested in interfacing with other network kit, so IS-IS is the beterer choice as openfabric is "dead" in IETF, replaced by the dist-opt-flood extensions to IS-IS)
Though Openfabric will happily insert onlink routes on unnumbered interfaces, it seems that IS-IS "needs" to have an IPv4 address on the interface(s), else it doesn't have next hops to insert.
I've searched high and low, and couldn't find any setting I've missed, and the source code hasn't been too helpful to see/understand if I'm missing something or if the needs haven't been coded into IS-IS yet.
My experience with IS-IS is only on Cisco and Juniper, so can't say much about FRR. I tried to get IS-IS on FRR on FreeBSD going a few years ago, but that ended in tears, so I abandoned it.
Unnumbered IS-IS interfaces will work for IPv6 because IPv6 always has a Link-Local address anyway.
In Cisco, unnumbered IS-IS interfaces work as long as the interface is in "point-to-point" mode. I see you have that mode in your configuration, so what it sounds like to me is that it is currently unsupported, or support is incomplete, on FRR.
As a hack, can you try routing a static IPv4 address via your unnumbered interfaces, without a next-hop target? I know that was a hack to create ARP glue for unnumbered interfaces on Cisco back in the day.
Mark.