Refer to the exhibit. You designed an IPv6 migration plan, and now you need to determine the impact on the existing IPv4 network. Assume default IS-IS parameters. What is likely to happen when you…

R2 has no IPv6 enabled on the link so IPv6 reachability does not apply to R2, and the single-topology SPF disruption affects IPv4 paths across all routers, not just the R3-R2 pair.

IS-IS floods LSPs to all neighbors through its flooding mechanism and cannot selectively advertise to only a subset of routers such as R1, R4, and R5.

The topology disruption caused by the single-topology mismatch breaks paths both to and through R2, meaning reachability loss is not limited to R2 alone but affects all routers relying on that link.

IS-IS default behavior is single-topology mode, meaning IPv4 and IPv6 share a single SPF tree and link-state database. When R3 enables IPv6 on the R3-R2 link, it begins advertising IPv6 TLVs in its LSPs, but R2 has not enabled IPv6 on its side. This creates a topology inconsistency in the single SPF tree that IS-IS cannot resolve, causing the link to be removed from the topology and breaking IPv4 loopback reachability for all routers that depended on that path.

IS-IS does not automatically generate or redistribute IPv6 default routes when IPv6 is enabled on an interface; no default IPv6 route would be sent from R3 to R2.