When configuring IPv4 and IPv6 IS-IS routing on Cisco IOS XR routers, which three statements
are correct? (Choose three.)

A.
By default, a single SPF is used for both IPv4 and IPv6, so the IPv4 and IPv6 topology should
be the same.

B.
By default, the IS-IS router type is Level 1 and Level 2.

C.
All IS-IS routers within the same IS-IS area must be configured with the same IS-IS routing
process instance ID.

D.
By default, metric-style narrow is used.

E.
By default, the IS-IS interface circuit type is Level 1 and Level 2.

F.
The area IS-IS address-family configuration command is used to specify the IS-IS area
address.

Explanation:

The default metric style for single topology is narrow metrics. However, you can use either wide
metrics or narrow metrics. How to configure them depends upon how single-topology is
configured. If both IPv4 and IPv6 are enabled and single-topology is configured, the metric style is
configured in the address-family ipv4 stanza. You may configure the metric style in the addressfamily ipv6 stanza, but it will be ignored in this case. If IPv6 only is enabled and single topology is
configured, then the metric style is configured in the address-family ipv6 stanza.