Two great IPv6 Goodies
If you are not familiar with IPv6 it works slightly differently then IPv4 when it comes to troubleshooting. One of the issues I ran into is that I depend on ARP often when dealing with Layer 2/3 issues. ARP as we know it in IPv4 doesn’t exist in IPv6. Instead it uses a part of ICMPv6 which is incorporated into the protocol called Neighbor Discovery (ND). The command to see directly connected IPv6 neighbors is:
show ipv6 neighbor ethernet 0/0
R1#show ipv6 neigh eth 0/0
IPv6 Address Age Link-layer Addr State Interface
FC00:192:1:12::2 22 aabb.cc00.0200 STALE Et0/0
FE80::A8BB:CCFF:FE00:200 9 aabb.cc00.0200 STALE Et0/0
R1#
Another command that is useful in IPv4 that I was not aware of and also works in IPv6 is the show ipv6 cef exact-route. In the example below FC00:1:1:1::1 is the loopback 0 interface. FC00:2:2:2::2 is the Loopback 0 interface of the connected neighbor R2 connected on Interface Ethernet 0/0.
R1#show ipv6 cef exact-route fc00:1:1:1::1 fc00:2:2:2::2
FC00:1:1:1::1 -> FC00:2:2:2::2 =>IPV6 adj out of Ethernet0/0, addr FE80::A8BB:CCFF:FE00:200
R1#show ipv6 neigh eth 0/0
IPv6 Address Age Link-layer Addr State Interface
FC00:192:1:12::2 22 aabb.cc00.0200 STALE Et0/0
FE80::A8BB:CCFF:FE00:200 9 aabb.cc00.0200 STALE Et0/0
