If you are not sure about HSRP, please read our HSRP tutorial.
The “standby track” command allows you to specify another interface on the router for the HSRP process to monitor in order to alter the HSRP priority for a given group. If the line protocol of the specified interface goes down, the HSRP priority is reduced. This means that another HSRP router with higher priority can become the active router if that router has standby preempt enabled.An example of using this command is shown below:
ip address 220.127.116.11 255.255.255.0
standby 1 ip 18.104.22.168
standby 1 priority 105
standby 1 preempt
standby 1 track Serial0
The default decrement priority value of HSRP is 10 so 1,5,20 are wrong values -> B, C and D are not correct.
In “standby 1 track 100” command, “100” is the tracked object number, not the decrement value. Here we don’t specify a decrement value so the default value will be used -> Answer A is correct. An example of configuring tracked object number with HSRP is shown below:
|Switch(config)# track 100 interface GigabitEthernet 0/0/0 line-protocol
Switch(config)#interface GigabitEthernet 0/0/0
Switch(config-if)# standby 1 track 100
If you want to specify a decrement value, we can use the “standby 1 track 100 decrement ” command instead.
The configuration of many hundreds of subinterfaces on the same physical interface, with each subinterface having its own HSRP group, can cause the processes of negotiation and maintenance of multiple HSRP groups to have a detrimental impact on network traffic and CPU utilization.
Only one HSRP group is required on a physical interface for the purposes of electing active and standby devices. This group is known as the master group. Other HSRP groups may be created on each subinterface and linked to the master group via the group name. These linked HSRP groups are known as client or slave groups.
The HSRP group state of the client groups follows that of the master group. Client groups do not participate in any sort of device election mechanism.
Client groups send periodic messages in order to refresh their virtual MAC addresses in switches and learning bridges. The refresh message may be sent at a much lower frequency compared with the protocol election messages sent by the master group.
The standby follow command configures an HSRP group to become an IP redundancy client of another HSRP group.
Client or slave groups must be on the same physical interface as the master group.
A client group takes its state from the master group it is following. Therefore, the client group does not use its timer, priority, or preemption settings. A warning is displayed if these settings are configured on a client group.
The following example shows how to configure HSRP group 2 as a client to the HSRP1 master group:
Router(config-if)# standby 2 follow HSRP1
From the output, we learn that the “Standby router is unknown” so we can conclude R2 cannot see other HSRP routers in this group. The problem can be a spanning-tree loop or a HSRP misconfiguration (for example another router is configured with virtual IP address of 10.10.1.1 but in different HSRP group). But from the error message we see R2 can still communicate via its Fa1/0 so the problem may not be a spanning-tree loop.