I want to make some adjustments to my network so I can add Layer 3 high availability.
- The changes I am having, separate DHCP servers, instead of using layer 3 router.
- Set the GW for router 1 to 192.168.VLAN.2 (Router on a stick – native vlan is 1)
- Add new router with GW to 192.168.VLAN.3 (Router on a stick)
- Confirm both IPs are reachable from my PCs

HSRP
- I want to use HSRP (Hot Standby Routing Protocol) between the two routers for high availability
- I am going to use the old router the active for VLAN 10, 20 and standby for VLAN 30, 40
- While I will use the new router as active for vlan 30, 40 and standby for 10.20
- If the WAN link goes down, I want to enable preempt to force the switch-over
- The priority will be set to 105 for the one I want to be active in the group and will keep the default for the standby (100) and for the link tracking the default of 10
Here we go:
For the old router, using this ocnfigurations for VLAN 10 & 20
HSRP-10-20(config)#int gig0/0.10
HSRP-10-20(config-subif)#standby 10 ip 192.168.10.1
%HSRP-6-STATECHANGE: GigabitEthernet0/0.10 Grp 10 state Speak -> Standby
%HSRP-6-STATECHANGE: GigabitEthernet0/0.10 Grp 10 state Standby -> Active
HSRP-10-20(config-subif)#standby 10 priority 105
HSRP-10-20(config-subif)#standby 10 preempt
HSRP-10-20(config-subif)#standby 10 track gigabitEthernet 0/2
HSRP-10-20#show standby
GigabitEthernet0/0.10 – Group 10 (version 2)
State is Active
4 state changes, last state change 02:14:02
Virtual IP address is 192.168.10.1
Active virtual MAC address is 0000.0C9F.F00A
Local virtual MAC address is 0000.0C9F.F00A (v2 default)
Hello time 3 sec, hold time 10 sec
Next hello sent in 0.426 secs
Preemption enabled
Active router is local
Standby router is unknown
Priority 105 (configured 105)
Track interface GigabitEthernet0/2 state Up decrement 10
Group name is hsrp–10 (default)
Using this configurations for VLAN 30 and 40 (standby)
HSRP-10-20(config)#int gig0/0.30
HSRP-10-20(config-subif)#standby 30 ip 192.168.30.1
HSRP-10-20(config-subif)#standby 30 preempt
HSRP-10-20(config-subif)#standby 30 track gigabitEthernet 0/2
Moving to the new router and making the configurations (same logic)
I found these lines so adorable not to share, while applying the preempt on this router:
%HSRP-6-STATECHANGE: GigabitEthernet0/0.40 Grp 40 state Speak -> Standby
HSRP-30-40(config-subif)#standby 40 preempt
HSRP-30-40(config-subif)#
HSRP-30-40(config-subif)#
%HSRP-6-STATECHANGE: GigabitEthernet0/0.40 Grp 40 state Standby -> Active
HSRP-30-40#show standby
GigabitEthernet0/0.10 – Group 10 (version 2)
State is Standby
3 state changes, last state change 02:26:25
Virtual IP address is 192.168.10.1
Active virtual MAC address is 0000.0C9F.F00A
Local virtual MAC address is 0000.0C9F.F00A (v2 default)
Hello time 3 sec, hold time 10 sec
Next hello sent in 2.327 secs
Preemption enabled
Active router is 192.168.10.2
Standby router is local
Priority 100 (default 100)
Track interface GigabitEthernet0/2 state Up decrement 10
Group name is hsrp–10 (default)
GigabitEthernet0/0.20 – Group 20 (version 2)
State is Standby
3 state changes, last state change 02:20:25
Virtual IP address is 192.168.20.1
Active virtual MAC address is 0000.0C9F.F014
Local virtual MAC address is 0000.0C9F.F014 (v2 default)
Hello time 3 sec, hold time 10 sec
Next hello sent in 1.533 secs
Preemption disabled
Active router is 192.168.20.2
Standby router is local
Priority 100 (default 100)
Track interface GigabitEthernet0/2 state Up decrement 10
Group name is hsrp–20 (default)
GigabitEthernet0/0.30 – Group 30 (version 2)
State is Active
15 state changes, last state change 02:27:04
Virtual IP address is 192.168.30.1
Active virtual MAC address is 0000.0C9F.F01E
Local virtual MAC address is 0000.0C9F.F01E (v2 default)
Hello time 3 sec, hold time 10 sec
Next hello sent in 2.481 secs
Preemption enabled
Active router is local
Standby router is 192.168.30.3, priority 105 (expires in 1 sec)
Priority 105 (configured 105)
Track interface GigabitEthernet0/2 state Up decrement 10
Group name is hsrp–30 (default)
GigabitEthernet0/0.40 – Group 40 (version 2)
State is Active
5 state changes, last state change 02:18:41
Virtual IP address is 192.168.40.1
Active virtual MAC address is 0000.0C9F.F028
Local virtual MAC address is 0000.0C9F.F028 (v2 default)
Hello time 3 sec, hold time 10 sec
Next hello sent in 2.24 secs
Preemption enabled
Active router is local
Standby router is 192.168.40.2, priority 105 (expires in 8 sec)
Priority 105 (configured 105)
Track interface GigabitEthernet0/2 state Up decrement 10
Group name is hsrp–40 (default)
Now, we reached the fun part of each lab .. the verifying 🙂
First thing I will reload one router and see how it goes

Second thing, I will kill the WAN link in the active router and see how it goes

The reason behind this, when the router is dead/ unreachable we will relay in the timers to figure this out, while when the link goes down the track command lower the priority immediately