On the right side you can see 2 multilayer switches. With those two switches I want to enable HSRP for each WAN router.
What has to be done in order to accomplish this? and why?
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The picture clearly shows a routing protocol between the routers and the 3560 switches, but for clarification, HSRP is configured as follows:
The standby ip interface configuration command activates HSRP on the configured interface. If an IP address is specified, that address is used as the designated address for the Hot Standby group. If no IP address is specified, the address is learned through the standby function. You must configure at least one Layer 3 port on the LAN with the designated address. Configuring an IP address always overrides another designated address currently in use.
When the standby ip command is enabled on an interface and proxy ARP is enabled, if the interface’s Hot Standby state is active, proxy ARP requests are answered using the Hot Standby group MAC address. If the interface is in a different state, proxy ARP responses are suppressed.
The above shows a segment of a network configured for HSRP. Each router is configured with the MAC address and IP network address of the virtual router. Instead of configuring hosts on the network with the IP address of Router A, you configure them with the IP address of the virtual router as their default router. When Host C sends packets to Host B, it sends them to the MAC address of the virtual router.
If for any reason, Router A stops transferring packets, Router B responds to the virtual IP address and virtual MAC address and becomes the active router, assuming the active router duties. Host C continues to use the IP address of the virtual router to address packets destined for Host B, which Router B now receives and sends to Host B.
Until Router A resumes operation, HSRP allows Router B to provide uninterrupted service to users on Host C’s segment that need to communicate with users on Host B’s segment and also continues to perform its normal function of handling packets between the Host A segment and Host B.
Configuration for example:
RouterA# configure terminal RouterA(config)# interface Vlan2 RouterA(config-if)# ip address 172.20.128.1 255.255.255.0 RouterA(config-if)# standby 1 ip 172.20.128.3 RouterA(config-if)# standby 1 priority 105 RouterA(config-if)# standby 1 preempt RouterA(config-if)# end RouterB# configure terminal RouterB(config)# interface Vlan2 RouterB(config-if)# ip address 172.20.128.2 255.255.255.0 RouterB(config-if)# standby 1 ip 172.20.128.3 RouterB(config-if)# standby 1 preempt RouterB(config-if)# end HostC: IP: 172.20.128.32 Subnet: 255.255.255.0 Gateway: 172.20.128.3