IS-IS, IPv4, and IPv6 in Service Provider Environments
Refer to the IS-IS configuration exhibit.
router isis 1
net 49.0001.0100.0100.1001.00
address-family ipv4 unicast
!
address-family ipv6 unicast
single-topology
!
interface gi0/0/0/0
address-family ipv4 unicast
!
address-family ipv6 unicast
This is the typical IS-IS configuration of the routers in an AS using IS-IS as the IGP. This AS is in the transition phase of integrating IPv6 into the network. During this transition phase, some of the routers within the AS might be running IPv4 only, some might be running IPv6 only, and others might be running both IPv4 and IPv6. To avoid any black holes for the IPv6 traffic, which configuration change can be made?
A.
Disable IS-IS adjacency checks.
B.
Enable IPv6 adjacency over IPv4 IS-IS peering.
C.
Enable multi-topology IS-IS.
D.
Disable the IPv4 unicast address-family.
E.
Enable IS-IS wide metric to support the single-topology mode.