The IOS-XR routers negotiate IPv6 unicast capability, but the generated
exabgp.conf declared only ipv4 unicast — producing repeated "route family
(ipv6/unicast) is not configured" errors that crashed ExaBGP. Declaring
ipv6 unicast on the neighbor matches the routers' capabilities and stops
the crash-restart cycle.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>