Information Technology Reference
In-Depth Information
To verify HSRP, use the show standby command.
The local state is active for the active router, as shown in Example 6-4. From the router output,
you can determine that Router A is the active HSRP router with a priority of 105 and that it can
preempt. Router A also tracks serial 0.
show standby Command on Router A
Example 6-4
routerA#show standby
Ethernet0 - Group 1
Local state is Active, priority 105, may preempt
Hellotime 3 holdtime 10 configured hellotime 3 sec holdtime 10 sec
Next hello sent in 00:00:02.500
Hot standby IP address is 192.168.1.1 configured
Active router is local
Standby router is 192.168.1.3 expires in 00:00:11
Standby virtual mac address is 0000.0c07.ac01
1 state changes, last state change 00:13:10
Tracking interface states for 1 interface, 1 up:
Up Serial0
The second router has a local state of standby, as shown in Example 6-5. From the router output,
you can determine that Router B is the HSRP standby router with a priority of 100. Router B
also tracks its interface serial 0. The output also shows that the default hellotime is 3 seconds
and the holdtime is 10 seconds.
show standby Command on Router B
Example 6-5
routerB6#show standby
Ethernet0 - Group 1
Local state is Standby, priority 100, may preempt
Hellotime 3 holdtime 10 configured hellotime 3 sec holdtime 10 sec
Next hello sent in 00:00:00.028
Hot standby IP address is 192.168.1.1 configured
Active router is 192.168.1.2 expires in 00:00:12, priority 105
Standby router is local
4 state changes, last state change 00:13:32
Tracking interface states for 1 interface, 1 up:
Up Serial0
ICMP
ICMP is defined by RFC 792. ICMP operates in the network layer and communicates error
messages between hosts and routers. ICMP uses several messages for different situations, for
example, when a packet cannot reach a destination, when the router cannot forward the packet,
or when the destination host cannot be reached. ICMP uses IP protocol number 1. ICMP returns
several message types, each with particular codes. The different message types are described in
Table 6-16.
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