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Chapter 8
Hot Standby Routing Protocol (HSRP)
Local state is Standby, priority 100
Hellotime 3 holdtime 10
Next hello sent in 00:00:01.628
Hot standby IP address is 10.1.0.200 configured
Active router is 10.1.0.1 expires in 00:00:09
Standby router is local
Standby virtual mac address is 0000.0c07.ac01
RouterB#
You can also see the virtual router address by looking at the ARP table on
a router. Remember that the Address Resolution Protocol (ARP) is used to
find a hardware (MAC) address from a known IP address. Once the ARP
protocol has resolved an IP address to a hardware address, the hardware
address is placed in the ARP cache for four hours. The next time the router
needs to communicate to a device connected on a LAN that is connected to
a router interface, the router will look in the ARP cache for the hardware
address. This makes the resolution faster than it would be if a broadcast were
sent every time. The command to see the ARP table is show ip arp. Here
is an example:
Router#sh ip arp
Protocol Address Age (min) Hardware Addr Type Interface
Internet 10.1.0.200 - 0000.0c07.ac01 ARPA FastEthernet0/0
Router#
Notice that the address 10.1.0.200 is in the ARP table and is resolved to
a hardware address. The router's F0/0 interface is configured with the IP
address, hence the dash (-) in the minute column. The 0000.0c is the Cisco
vendor code. The 07.ac is the HSRP Well-Known Virtual MAC Address.
The 01 is the HSRP group number.
After both routers have been configured, they begin transmitting hello
packets every three seconds to the multicast address 224.0.0.2. This is shown
in the output below:
SB1:Ethernet0 Hello out 10.1.0.2 Standby pri 100 hel 3 hol
10 ip 10.1.0.200
SB1:Ethernet0 Hello in 10.1.0.1 Active pri 100 hel 3 hol
10 ip 10.1.0.200
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