[Babel-users] High CPU usage & instability with full IPv6 table

[Toke Høiland-Jørgensen]

"Steven Honson" <babel-users at steven.honson.au> writes:

> Hello there.
>
> I operate a small personal IPv6-only network under my own AS, mainly
> for learning purposes, with the core of it being compromised of four
> main hosts spread around the world in a mesh topology. Each has a full
> IPv6 table, as I connect to a variety of transit providers and IXs on
> different routers. I obviously use BGP as my Exterior Routing
> Protocol, but use Babel as my Interior Routing Protocol between the
> four hosts.
>
> At the moment I am using Bird 2 to handle both BGP and Babel, and it
> barely breaks a sweat, but would like to use babeld for the Babel
> component so to be able to leverage some of the additional features
> that the Bird implementation lacks.

Which feature(s) are you missing in Bird? :)

> I've ran in to an issue though where babeld hits the ceiling with CPU
> usage the moment I start it and has some trouble maintaining reliable
> neighbor connections. This does not subside.
>
> Even if I disable the redistribution and installation of all routes
> using the following configuration options, and have the rest as a
> stock standard minimal configuration, I see this behavior remain:
>
> local-port 33123
> interface wg-1
> interface wg-2
> interface wg-3
> redistribute local deny
> install deny
>
> My routers are low-end VPSs, most having 1GB of RAM, with around half
> of this, and a single vCPU, and are all running Alpine Linux. In terms
> of IPv6 routes, a quick check reveals that the kernel routing table is
> holding about ~150,000 routes, though only a handful of those are ones
> that I have babel managing since it is only playing the role of an
> IGP.
>
> Any clues what sort of limit I may have reached or how to mitigate
> this? Is the CPU being eaten up constantly monitoring and filtering
> route changes in my kernel routing table due to the constant churn of
> the global IPv6 table?

Sounds like you could be hitting the same issue as described in this
thread?

https://alioth-lists.debian.net/pipermail/babel-users/2022-February/003884.html

-Toke