[j-nsp] 6PE without family inet6 labeled-unicast

[Pavel Lunin]

On Sun, Jul 22, 2018 at 9:45 PM, Andrey Kostin <ankost at podolsk.ru> wrote:

> Hi Pavel,
>
> Thanks for replying. I understand how it works as soon as proper next-hop
> is present in a route. My attention was attracted by implicit next-hop
> conversion from pure IPv4 address to IPv4-mapped IPv6 next-hop from
> "Nexthop: YYY.YYY.155.141" in the advertised route to "Protocol next hop:
> ::ffff:YYY.YYY.155.141" in the received route.
>

This is normal. In order to announce AFI/SAFI 2/1 update, you must have an
IPv6 next-hop. This is why it gets automatically converted. If you enable
BGP-LU, nothing will change in this terms, your next-hop address will still
be an IPv4-mapped IPv6 address. It will just be labeled.

Same thing happens when you perform next-hop-self (or it's eBGP) for an
IPv6 route, announced via an MP-BGP session over IPv4.

And ipv6-tunneling under mpls stanza is what makes your LDP/RSVP routes be
leaked from inet.3 to inet6.3 with automatic v4-to-v6 mapping. It's a
syntactic sugar, you can do the same with policies, explicitly leaking
inet.3 to inet6.3.

I'm also wondering what could happen is there are no LSP available, which
> is rather unreal situation because everything will be broken anyway in this
> case.
>
If no LSP/FEC is available for the v4-mapped IPv6 next-hop, you won't have
an LDP/RSVP route in inet.3, thus it won't be leaked to inet6.3. So your
BGP route will not be inactive because of the unreachable next-hop. And
not, it's not so unusual. You can easily have your IGP up and running, but
someone forgot to add MPLS on one of the core interfaces. So your BGP
session and routes are up, IGP works but there is no labeled next-hop in
inet.3.

--
Pavel