To monitor HSRP settings, you can use the show standby command. The show standby command displays a router's state and which router is active. Listing 5.4 displays the output from the show standby command.
Listing 5.4 The show standby command.
Ethernet0 - Group 0
Local state is Active, priority 120, may preempt
Hellotime 3 holdtime 10
Next hello sent in 00:00:01.108
Hot standby IP address is 22.214.171.124 configured
Active router is local
Standby router is 126.96.36.199 expires in 00:00:08 Tracking interface states for 1 interface, 1 up: Up Serial0
Listing 5.4 is taken from Router R1, and it displays R1's local state as active. This means that Router R1 has assumed the role of the default gateway. Other valid router states are speak (negotiating who will become the default gateway, highest priority will win) and standby (backup router).
Theoretically, end users will not see any significant network outage if one of the routers or interfaces becomes unreachable. The ARP protocol will resolve the new Virtual MAC address and hosts will start to use R2 as the default gateway.
HSRP is supported over Token Ring and ATM LANE (IOS 11.2+) networks.
Now that we've reviewed some of the functions of the IP layers and how you can provide a resilient network, let's look at a typical Transport Control Program session running over the IP layer, including how a typical TCP session is started and terminated.
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