# HSRP, VRRP, and GLBP

> Markdown source of <https://docs.calebsargeant.com/networking/cisco/switching/redundancy-in-the-campus/>.

## Redundancy Considerations

- How fast can this happen?
- How does the client know?
- What about ARP cache issues?
- What if just the WAN link fails?

## HSRP vs VRRP vs GLBP

- Cisco Hot-Standby Router Protocol (HSRP):
  - Created by Cisco, for Cisco in 1994
  - Uses a default hello timer of 3 seconds with a hold timer of 10 seconds
- Virtual Router Redundancy Protocol (VRRP):
  - Created by the IETF in 1999
  - Works between multiple vendors
  - Has faster timers than HSRP by default - hello of 1 second, hold timer of 3 seconds
- Gateway Load Balancing Protocol (GLBP):
  - Created by Cisco, for Cisco in 2005
  - Identical features to HSRP, but allows active-active connection that adds load balancing

## HSRP

- Gateways organised into standby groups
- One gateway active, others in standby state
- Phantom (virtual) router IP and MAC address generated
- Hello messages sent once every 3 seconds, dead after 10 sec

Mac Address Structure:

- 0000.0C07.ACXX
- 0000.0C - Cisco Vendor ID
- 07.AC - HSRP ID
- XX - Standby group number

### HSRP Base Configuration

- Step 1: Create standby group
- Step 2: Reassign IP Addresses
- Step 3: Verify
- Step 4: optimize and tune

``` text
# Switch A
int vlan 70
standby 1 ip 172.30.70.1
standby 1 priority 150
# Switch B (default priority of 100)
int vlan 70
standby 1 ip 172.30.70.1
standby 1 priority 100

# Verify
show standby
```

### Tuning and Optimizing HSRP

- Priority
- Preempt
- Tracking
- Timers

``` text
standby group 1 preempt
standby 1 track f0/23 60
standby 1 preempt delay reload 180
standby 1 timers msec 150 msec 700
```

## VRRP

- Active/standby becomes master/backup
- Standby group becomes VRRP group
- master router can share virtual IP
- One second hello timer, three times hello = down time (+ skew timer)

### VRRP Configuration

- Step 1: Configure VRRP Group
- Step 2: Optimize settings
- Step 3: Verify

``` text
# Master
int f0/0
vrrp 20 ip 172.30.4.90
vrrp 20 preempt
vrrp 20 timers advertise msec 100
# Backup
# same, except instead of advertise, learn

# Verify
show vrrp
```

## GLBP

- Single VIP with Multiple MACs
- Active Virtual gateway (AVG) acts as the 'point man'
- Other routers act as active virtual forwarders (AVF)

### GLBP Configuration

``` 
# AVG
int f0/0
glbp 1 ip 172.30.4.70
glbp 1 priority 150

# AVF
# get priority 100

# other options
glbp 1 load-balancing
glbp 1 timers
glbp 1 weighting

# Verify
show glbp
```