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MPLS L3VPN IPv6 address-family over IPv4 MPLS backbone
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Description

Tested on VyOS VyOS 1.4-rolling-202110180513
When testing the MPLS L3VPN it turns out that IPv6 routes are not added to PE routers. IPv4 works as it should.

Research has shown that VyOS behavior is not consistent with the RFC rfc4798
The first problem is related to BGP Next hop. According to the RFC:

the 6PE routers convey their IPv4 address as the BGP Next Hop for the advertised IPv6 prefixes.
The IPv4 address of the egress 6PE router MUST be encoded as an IPv4-mapped IPv6 address in the BGP Next Hop field.

In VyOS instead of IPv4-mapped IPv6 address we see IPv6 Link-Local address:

   Network          Next Hop            Metric LocPrf Weight Path
Route Distinguisher: 65003:3003
*>ifc:3::/64        fe80::200:ff:fe00:0

Second
When trying to fix IPv6 Next hop via route-map on RFC, the route is installed in IPv6 routing table and looks better:

   Network          Next Hop            Metric LocPrf Weight Path
Route Distinguisher: 65003:3003
*>ifc:3::/64        ::ffff:a00:3             0    100      0 i

IPv6 routes even get into the routing table of the desired VRF (but as "r - rejected"):

K>* ::/0 [255/8192] unreachable (ICMP unreachable), 1d00h03m
B>r fc:3::/64 [200/0] via ::ffff:a00:3 (vrf default) (recursive), label 81, weight 1, 00:08:50
  r                     via 2.2.2.10, eth2 (vrf default), label 16/81, weight 1, 00:08:50

There are no routes in the kernel:

vyos@VyOS-PE2:~$ ip -6 -a route show vrf INET
::1 dev INET proto kernel metric 256 pref medium
unreachable default dev lo metric 4278198272 pref medium

Zebra logs:

Nov 01 08:24:59 VyOS-PE2 zebra[813]: Extended Error: IPv6 routes can not use an IPv4 nexthop
Nov 01 08:24:59 VyOS-PE2 zebra[813]: [EC 4043309093] netlink-dp (NS 0) error: Invalid argument, type=RTM_NEWROUTE(24), seq=214, pid=3971021444
Nov 01 08:24:59 VyOS-PE2 zebra[813]: INET(9:800):fc:3::/64: Route install failed

Similar problem in FRRouting:
BGPv6 LU can't install routes into Zebra/Kernel and then crashes #7035

Details

Difficulty level
Unknown (require assessment)
Version
1.4-rolling-202110180513
Why the issue appeared?
Will be filled on close
Is it a breaking change?
Unspecified (possibly destroys the router)
Issue type
Unspecified (please specify)

Event Timeline

Unknown Object (User) created this task.Nov 2 2021, 8:07 AM
Unknown Object (User) created this object in space S1 VyOS Public.

Yes, It seems that rfc doesn't work , also I found this issues :
https://github.com/FRRouting/frr/issues/5824

I'm going to ask to FRRounting , if they found any solution about it.

Viacheslav triaged this task as Wishlist priority.Jan 20 2024, 2:56 AM