PT LAB: Bringing up Nours small network – Layer 3 High Availability (HSRP)

I want to make some adjustments to my network so I can add Layer 3 high availability.

  1. The changes I am having, separate DHCP servers, instead of using layer 3 router.
  2. Set the GW for router 1 to 192.168.VLAN.2  (Router on a stick – native vlan is 1)
  3. Add new router with GW to 192.168.VLAN.3  (Router on a stick)
  4. Confirm both IPs are reachable from my PCs

L3-HA

 

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

HSRP-reload-active

 

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

HSRP-kill-link

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

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