[VRF] Install IPv6 link local route for new VRF

[iMasaruOki]

Signed-off-by: Masaru OKI [email protected]

What I did Fix for issue: Azure/sonic-buildimage#8831

Why I did it When created new VRF, IPv6 link local route is not installed for the VRF. It causes BGP unnumbered (ipv4 route via ipv6 nexthop) is not working.

How I verified it

Ethernet0 of DUT is connected to another switch speaking BGP (ASN 100).

Setting:

sudo config vrf add Vrf1
sudo config interface vrf bind Ethernet0 Vrf1
sudo config ipv6 enable link-local
vtysh \
-c "conf t" \
-c "router bgp 100 vrf Vrf1" \
-c "  router-id 1.1.1.1" \
-c "  neighbor Ethernet0 interface remote-as internal"

Wait for minutes, and run vtysh -c 'show bgp vrf all summary'

Details if related

[prsunny]

@AkhileshSamineni, please review