Troubleshooting Gateway Redundancy Protocols
HSRP configuration and verification

The steps to configure HSRP are listed In figures .

Configure HSRP Group on an Interface
While running HSRP, it is important that the end-user stations do not discover the actual MAC addresses of the routers in the standby group. Any protocol that informs a host of the router actual address must be disabled. To ensure that the actual addresses of the participating HSRP routers are not discovered, enabling HSRP on a Cisco router interface automatically disables ICMP redirects on that interface.

After the standby ip command is issued, the interface changes to the appropriate state. When the router successfully executes the command, the router issues an HSRP message.

To remove an interface from an HSRP group, enter the no standbygroup ip command .

Verifying HSRP Configuration
The following example states that interface VLAN10 is a member of the HSRP standby group 47, the virtual router IP address for that group is 172.16.10.110, and that ICMP redirects are disabled:

Switch#show running-config
Building configuration...
Current configuration:
!
(text deleted)
interface Vlan10
ip address 172.16.10.82 255.255.255.0
no ip redirects
standby 47 ip 172.16.10.110
!

Another means of verifying the HSRP configuration is with the command :

Switch#show standby brief

This command displays abbreviated information about the current state of all HSRP operations on this device.

Establish HSRP Priorities
Each standby group has its own active and standby routers. The network administrator can assign a priority value to each router in a standby group, allowing the administrator to control the order in which active routers for that group are selected .

To set the priority value of a router, enter this command in interface configuration mode :

Switch(config-if)#standby group-number priority priority-value

During the election process, the router in an HSRP group with the highest priority becomes the forwarding router. In the case of a tie, the router with the highest configured IP address will become active.

To reinstate the default standby priority value, enter the no standby priority command.

Verify the HSRP Standby Priority
The following example states that interface VLAN10 has a priority value of 150 in HSRP standby group 47. If this priority value is the highest number in that HSRP standby group, the routing device on which this interface resides is the active router for that group.

Switch#show running-config
Building configuration...
Current configuration:
!
(text deleted)
interface Vlan10
ip address 172.16.10.32 255.255.255.0
no ip redirects
standby 47 priority 150
standby 47 ip 172.16.10.110

To display the status of the HSRP router, enter one of these commands:

Switch#show standby [interface [group]] [active | init | listen | standby][brief]
Switch#show standby delay [type-number]

If the optional interface parameters are not indicated, the show standby command displays HSRP information for all interfaces.

Verify all HSRP Operations
This example shows the output of the show standby command:

Switch#show standby Vlan10 47
Vlan11 - Group 47
Local state is Active, priority 150, may preempt
Hellotime 3 holdtime 10
Next hello sent in 00:00:02.944
Hot standby IP address is 172.16.10.110 configured
Active router is local
Standby router is 172.16.10.82 expires in 00:00:08
Standby virtual mac address is 0000.0c07.ac2f
Tracking interface states for 1 interface, 1 up:
Up Vlan51 Priority decrement: 40

This is an example of the output resulting when you specify the brief parameter:

Switch#show standby brief
Interface Grp Prio P State Active addr Standby addr Group addr
Vl10 47 150 P Active local 172.16.10.82 172.16.11.10
Vl12 12 100 Standby 172.16.102.82 local 172.16.12.10

HSRP Standby Preempt
The standby router automatically assumes the active router role when the active router fails or is removed from service. This new active router remains the forwarding router even when the former active router with the higher priority regains service in the network.

The former active router can be configured to resume the forwarding router role from a router with a lower priority . To enable a router to resume the forwarding router role, enter the following command in interface configuration mode:

Switch(config-if)#standby [group-number] preempt [{delay} [minimum delay] [sync delay]]

When the standby preempt command is issued, the interface changes to the appropriate state.

To remove the interface from preemptive status, enter the no standbygroup preempt command.

Example: Displaying HSRP Preempt
The following example states that interface VLAN10 is configured to resume its role as the active router in HSRP group 47, assuming that interface VLAN10 on this router has the highest priority in that standby group.

Switch#show running-config
Building configuration...
Current configuration:
!
(text deleted)
interface Vlan10
ip address 172.16.10.82 255.255.255.0
no ip redirects
standby 47 priority 150
standby 47 preempt
standby 47 ip 172.16.10.110