Layer-3 core: SVIs, HSRP, OSPF and deterministic spanning-tree root placement.
Higher wins. Use 110 on primary, 100 on secondary.
hostname core-01
!
ip routing
!
! Root placement is a decision, not something to let MAC addresses settle.
spanning-tree mode rapid-pvst
spanning-tree vlan 1-4094 priority 4096
!
vlan 10
name USERS
!
interface Vlan10
description Users gateway
ip address 10.0.10.2 255.255.255.0
standby version 2
standby 10 ip 10.0.10.1
standby 10 priority 110
standby 10 preempt delay minimum 60
standby 10 timers msec 250 msec 750
no shutdown
!
router ospf 1
router-id 10.255.0.1
auto-cost reference-bandwidth 100000
passive-interface default
no passive-interface Vlan10
network 10.0.10.2 0.0.0.255 area 0
!
! preempt delay gives the box time to converge before it takes the VIP back,
! otherwise it blackholes traffic while routing is still coming up.
!
end