The MIB module provides a means to monitor and configure the Cisco IOS proprietary Hot Standby Router Protocol (HSRP). Cisco HSRP protocol is defined in RFC2281.
HSRP is a protocol used amoung a group of routers for the purpose of selecting an ‘active router’ and a ‘standby router’.
An ‘active router’ is the router of choice for routing packets.
A ‘standby router’ is a router that takes over the routing duties when an active router fails, or when preset conditions have been met.
An ‘HSRP group’ or a ‘standby group’ is a set of routers which communicate using HSRP. An HSRP group has a group MAC address and a group Virtual IP address. These are the designated addresses. The active router assumes (i.e. inherits) these group addresses.
‘Hello’ messages are sent to indicate that a router is running and is capable of becoming the active or standby router.
‘Hellotime’ is the interval between successive HSRP Hello messages from a given router.
‘Holdtime’ is the interval between the receipt of a Hello message and the presumption that the sending router has failed.