What command can be used on a Cisco switch to display the virtual MAC address for the HSRP groups of which the switch is a member?
switch# show standby mac
switch# show hsrp mac
switch# show standby
switch# show standby brief
The command show standby can be used to display the virtual MAC address for HSRP groups of which a switch is a member. This command displays information about HSRP on all configured interfaces and for all HSRP groups. It also displays hello timer information and the expiration timer for the standby switch. The standby switch will take over as the active switch if the timer expires before it hears a heartbeat from the active switch. Below is an example of the show standby command for the HSRP group 1:
In the above output, the following can be determined:
- The router is currently active for the group, as can be seen in line 2. The Active Virtual MAC address is 0006.6b45.5801, which includes the group number (1) in the last two positions, which is why the address is different from the routers actual MAC address shown on the next line. Special Note: Some router models (Cisco 2500, 4000 and 4500) WILL NOT use this altered MAC address format, but will instead use the real MAC address for the virtual MAC address and will display that MAC address as the virtual MAC address in the output of the show standby command. An example of the output of the show standby command on an older router such as the 2500 would be as follows:
These routers have Ethernet hardware that only recognize a single MAC address. In either case, if for some reason this router becomes the standby router, such as due to loss of interfaces, then when the interfaces come back up it will be able to recover the active role because it is set for preemption, as shown on line 10.
- The router is tracking two of its own interfaces. Because both interfaces are down, the router’s priority has been reduced by 25 (15 for Fastethernet0/2 and 10 for Fastethernet0/3), from the configured value of 120 to 95. This data is shown on lines 13-16. The default is 10 if not otherwise specified, as is the case for Fastethernet0/3.
- If either of the two interfaces comes back up, the priority will be increased by the amount assigned to the interface. For example, if Fastethernet0/3 comes back up, the priority will become 105 (95 + 10).
- The standby router is unreachable, which can be determined because it is marked unknown expired in line 12. This could be due to either a physical layer issue or an HSRP misconfiguration.
The command show standby brief can be used to view summary information about HSRP groups of which the switch is a member. This information includes the group number, priority, state, active device address, standby address, and group address. It does not include the virtual MAC address.
The commands show standby mac and show hsrp mac are invalid due to incorrect syntax.
Configure and verify first-hop redundancy protocols