To protect against first-hop router failure, four protocols were developed to ensure IP routing
redundancy. Which of the following are they? (Select four)

A.
HSRP

B.
IRDP

C.
ICMP

D.
VRRP

E.
MSTP

F.
GLBP

Explanation:
A: HSRP is the Hot Standby Routing Protocol, which is the Cisco proprietary method for
automatic failover and provides for redundant default gateways for hosts.
B: Some newer IP hosts use the 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.
D: VRRP is the Virtual Router Redundancy Protocol, which is similar in many ways to HSRP.
One key difference is that VRRP is standards based, where HSRP is Cisco developed.
F: Gateway Load Balancing Protocol (GLBP) protects data traffic from a failed router or
circuit, like Hot Standby Router Protocol (HSRP) and Virtual Router Redundancy Protocol
(VRRP), while allowing packet load sharing between a group of redundant routers.