What protocol specified by RFC 1256 will allow an enabled IP host a new router when a
router becomes unavailable?

A.
IRDP

B.
SNMP

C.
HSRP

D.
VRRP

Explanation:
Some newer IP hosts use ICMP Router Discovery Protocol (IRDP) (RFC 1256) to find a new
router when a route becomes unavailable. A host that runs IRDP listens for hello multicast
messages from its configured router and uses an alternate router when it no longer receives
those hello messages. The default timer values of IRDP mean that it’s not suitable for
detection of failure of the first hop. The default advertisement rate is once every 7 to 10
minutes, and the default lifetime is 30 minutes.