on 3845
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ip address 55.55.55.2 x.x.x.x (X = subnet mask)
standby 10 ip x.x.x.x - X is the gateway IP should be same on both the Router
standby 10 preempt
on VXR
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ip address 55.55.55.1 x.x.x.x (X = subnet mask)
standby 10 ip x.x.x.x - X is the gateway IP should be same on both the Router
standby 10 priority 105 ( makes VXR as active )
standby 10 preempt
If you have 55.55.55.3 IP free have that configured on VXR interfaceand have 55.55.55.1 has gateway