GLBP example with interface tracking
This document provide you the detail steps to configure GLBP between two locations. As we know that we can use GLBP for load balancing between two links or locations, so that there is no dependency on the single link.
If we have two links we can simply configure GLBP and load balancing works. But, if other location also have two links then how we will configure GLBP to achieve the same?
Refer the diagram above, In Core switch there is only one default route towards the router and the gateway will be the glbp ip. Now assume, if p2p link of router 1 of site A goes down then traffic will go through the router 2, but from site B they don't know that router 1 of site A is down and they will send traffic through both the router due to the default behavior (round robin) of GLBP and hence some systems from site B will not be able to access site A resources.
To resolve this issue we need to do IP SLA from both the side and need to track its gateway so that if any of the link goes down both the router connected through that link will know that there is no reachability let the traffic to go from other link.
So below is the configuration example
Configuration Details
Configuration on router 1
This document provide you the detail steps to configure GLBP between two locations. As we know that we can use GLBP for load balancing between two links or locations, so that there is no dependency on the single link.
If we have two links we can simply configure GLBP and load balancing works. But, if other location also have two links then how we will configure GLBP to achieve the same?
Refer the diagram above, In Core switch there is only one default route towards the router and the gateway will be the glbp ip. Now assume, if p2p link of router 1 of site A goes down then traffic will go through the router 2, but from site B they don't know that router 1 of site A is down and they will send traffic through both the router due to the default behavior (round robin) of GLBP and hence some systems from site B will not be able to access site A resources.
To resolve this issue we need to do IP SLA from both the side and need to track its gateway so that if any of the link goes down both the router connected through that link will know that there is no reachability let the traffic to go from other link.
So below is the configuration example
Configuration Details
Detailed Steps
Configuration on router 1
Enabling IP SLA
Steps
|
Command or Action
|
Step 1
|
Ssh or telnet to router
|
Step 2
|
Router> enable
|
Step 3
|
Router# configure terminal
|
Step 4
|
Router(config)# ip sla 1
|
Step 5
|
icmp-echo 10.10.1.2 source-interface GigabitEthernet0/1
|
Step 6
|
Router(config)# ip sla schedule 1 life forever start-time now
|
Track ip sla
To track the state of a Cisco IOS IP SLA operation and to enter tracking configuration mode, use the below command on configuration mode
Step 7
|
router(config)#track 1 ip sla 1
reachability
|
GLBP Configuration
Command or Action
| |
Step 1
|
Ssh or telnet to router
|
Step 2
|
Router> enable
|
Step 3
|
Router# configure terminal
|
Step 4
|
Router(config)# interface Gi 0/0
|
Step 5
|
Router(config)#ip address 10.10.10.9 255.255.255.0
|
Step 6
|
Router(config-if)# glbp 10 preempt
|
Step 7
|
Router(config-if)# glbp 10 ip 10.10.10.11
|
Step 8
|
Router(config-if)# glbp 10 weighting track 1 decrement 100
|
Step 9
|
Router(config-if)# exit
|
Configuration on router 2
Steps
|
Command
or Action
|
Step 1
|
Ssh or telnet to router
|
Step 2
|
Router> enable
|
Step 3
|
Router# configure terminal
|
Step 4
|
Router(config)# ip sla 1
|
Step 5
|
icmp-echo 10.10.1.1 source-interface
GigabitEthernet0/1
|
Step 6
|
Router(config)# ip sla schedule
1 life forever start-time now
|
Step 7
|
router(config)#track 1 ip sla 1
reachability
|
GLBP
Configuration
Command
or Action
|
|
Step 1
|
Ssh or telnet to router
|
Step 2
|
Router> enable
|
Step 3
|
Router# configure terminal
|
Step 4
|
Router(config)# interface Gi
0/0
|
Step 5
|
Router(config)#ip address 10.5.10.9
255.255.255.0
|
Step 6
|
Router(config-if)# glbp 10 preempt
|
Step 7
|
Router(config-if)# glbp 10 ip
10.5.10.11
|
Step 8
|
Router(config-if)# glbp 10 weighting
track 1 decrement 100
|
Step 9
|
Router(config-if)# exit
|
Configuration on router 3
Steps
|
Command or Action
|
Step 1
|
Ssh or telnet to router
|
Step 2
|
Router> enable
|
Step 3
|
Router# configure terminal
|
Step 4
|
Router(config)# ip sla 1
|
Step 5
|
icmp-echo 10.10.2.1 source-interface GigabitEthernet0/1
|
Step 6
|
Router(config)# ip sla schedule 1 life forever start-time now
|
Step 7
|
router(config)#track 1 ip sla 1 reachability
|
GLBP Configuration
Command or Action
| |
Step 1
|
Ssh or telnet to router
|
Step 2
|
Router> enable
|
Step 3
|
Router# configure terminal
|
Step 4
|
Router(config)# interface Gi 0/0
|
Step 5
|
Router(config)#ip address 10.10.10.10 255.255.255.0
|
Step 6
|
Router(config-if)# glbp 10 preempt
|
Step 7
|
Router(config-if)# glbp 10 ip 10.10.10.11
|
Step 8
|
Router(config-if)# glbp 10 weighting track 1 decrement 100
|
Step 9
|
Router(config-if)# exit
|
Configuration on router 4
Steps
|
Command or Action
|
Step 1
|
Ssh or telnet to router
|
Step 2
|
Router> enable
|
Step 3
|
Router# configure terminal
|
Step 4
|
Router(config)# ip sla 1
|
Step 5
|
icmp-echo 10.10.2.1 source-interface GigabitEthernet0/1
|
Step 6
|
Router(config)# ip sla schedule 1 life forever start-time now
|
Step 7
|
router(config)#track 1 ip sla 1 reachability
|
GLBP Configuration
Command or Action
| |
Step 1
|
Ssh or telnet to router
|
Step 2
|
Router> enable
|
Step 3
|
Router# configure terminal
|
Step 4
|
Router(config)# interface Gi 0/0
|
Step 5
|
Router(config)#ip address 10.5.10.10 255.255.255.0
|
Step 6
|
Router(config-if)# glbp 10 preempt
|
Step 7
|
Router(config-if)# glbp 10 ip 10.5.10.11
|
Step 8
|
Router(config-if)# glbp 10 weighting track 1 decrement 100
|
Step 9
|
Router(config-if)# exit
|
