Arista BGP Peering Options (2) - IPv4 NRLI over IPv6 Peering

Here is the TOI link

On the top of regular IPv6 BGP configuration, you need to configure 2 things:

1) Enable IPv4 NLRI over v6 peering and 2 ways to do it:

1. Under ipv4 address-family, activate it on ipv6 peering, which is shown in R1's configuration
2. Global configuration of "bgp default ipv4-unicast transport ipv6" in R2's show run

2) Specify the IPv4 NH of IPv4 prefixes, and we can do it 3 ways:

1. Global automatic NH address - "bgp auto-local-addr" in R'2 configuration. But this is a global knob, so if you have IPv6 prefixes over IPv4 NH, it will break peering silently. 
2. Neighbor-base automatic NH address - "neighbor 12:12:101::1 auto-local-addr"
3. Neighbor-base manual NH address in R1's configuration - "neighbor 12:12:101::2 local-v4-addr 12.12.101.1"

Here is the output of "sh ip bgp 101.2.2.0" (I enable "routing-context vrf v1", so no need vrf)

R1.lp231.16:28:58(config)#sh ip bgp 101.2.2.0

BGP routing table information for VRF v1

Router identifier 101.1.1.1, local AS number 1

BGP routing table entry for 101.2.2.0/24

 Paths: 1 available

  2

    12.12.101.2 from 12:12:101::2 (101.2.2.2)

      Origin IGP, metric 0, localpref 100, IGP metric 1, weight 0, received 00:02:03 ago, valid, external, best

      Rx SAFI: Unicast

And both ipv4/ipv6 ping work as expected. 

R1.lp231.16:29:11(config)#ping 101.2.2.2

PING 101.2.2.2 (101.2.2.2) 72(100) bytes of data.

80 bytes from 101.2.2.2: icmp_seq=1 ttl=64 time=0.242 ms

80 bytes from 101.2.2.2: icmp_seq=2 ttl=64 time=0.100 ms

80 bytes from 101.2.2.2: icmp_seq=3 ttl=64 time=0.093 ms

80 bytes from 101.2.2.2: icmp_seq=4 ttl=64 time=0.091 ms

80 bytes from 101.2.2.2: icmp_seq=5 ttl=64 time=0.093 ms

--- 101.2.2.2 ping statistics ---

5 packets transmitted, 5 received, 0% packet loss, time 0ms

rtt min/avg/max/mdev = 0.091/0.123/0.242/0.060 ms, ipg/ewma 0.174/0.180 ms

R1.lp231.16:31:39(config)#ping ipv6 101:2:2::2

PING 101:2:2::2(101:2:2::2) 72 data bytes

80 bytes from 101:2:2::2: icmp_seq=1 ttl=64 time=0.262 ms

80 bytes from 101:2:2::2: icmp_seq=2 ttl=64 time=0.106 ms

80 bytes from 101:2:2::2: icmp_seq=3 ttl=64 time=0.103 ms

80 bytes from 101:2:2::2: icmp_seq=4 ttl=64 time=0.099 ms

80 bytes from 101:2:2::2: icmp_seq=5 ttl=64 time=0.103 ms

--- 101:2:2::2 ping statistics ---

5 packets transmitted, 5 received, 0% packet loss, time 0ms

rtt min/avg/max/mdev = 0.099/0.134/0.262/0.064 ms, ipg/ewma 0.184/0.196 ms