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An example of GLBP:

I have a simple example of GLBP:

R1:

interface FastEthernet0/1

description Link to LAN

ip address 172.16.9.6 255.255.255.0

duplex auto

speed auto

glbp 10 ip 172.16.9.1

glbp 10 priority 200

glbp 10 preempt delay minimum 60

glbp 10 weighting 110 lower 95 upper 105

glbp 10 weighting track 1 decrement 20

glbp 10 forwarder preempt delay minimum 10

glbp 20 ip 172.16.9.4

glbp 20 priority 254

glbp 20 preempt delay minimum 60

glbp 20 weighting 110 lower 95 upper 105

glbp 20 weighting track 1 decrement 20

glbp 20 forwarder preempt delay minimum 10

r2:

interface FastEthernet0/1

description Link to LAN

ip address 172.16.9.5 255.255.255.0

duplex auto

speed auto

glbp 10 ip 172.16.9.1

glbp 10 priority 254

glbp 10 preempt delay minimum 60

glbp 10 weighting 110 lower 95 upper 105

glbp 10 weighting track 1 decrement 20

glbp 10 forwarder preempt delay minimum 20

glbp 20 ip 172.16.9.4

glbp 20 priority 200

glbp 20 preempt delay minimum 60

glbp 20 weighting 110 lower 95 upper 105

glbp 20 weighting track 1 decrement 20

glbp 20 forwarder preempt delay minimum 20

Can I say that R1 is thg active Gataway for GLBP 20, while R2 is the active Gateway for GLBP 10?

and, how to assign the default gateway of the LAN PC? 172.16.9.4 or 172.16.9.1?

Can I say that the best pratise is assign half PC to 172.16.9.1 and the other half is 172.16.9.4?

1 REPLY

Re: An example of GLBP:

Hello,

the idea of GLBP is to assigne one default gateway IP to all the hosts in a subnet and do the load balancing through GLBP. Hence the name is Gateway Load Balancing Protocol.

This is achieved by answering the ARPs for the gateway IP of PCs with different MAC addresses of the different participating routers - the active virtual forwarders.

Thus the config above can be simplified:

R1:

interface FastEthernet0/1

description Link to LAN

ip address 172.16.9.6 255.255.255.0

duplex auto

speed auto

glbp 10 ip 172.16.9.1

glbp 10 priority 200

glbp 10 preempt delay minimum 60

glbp 10 weighting 110 lower 95 upper 105

glbp 10 weighting track 1 decrement 20

glbp 10 forwarder preempt delay minimum 10

r2:

interface FastEthernet0/1

description Link to LAN

ip address 172.16.9.5 255.255.255.0

duplex auto

speed auto

glbp 10 ip 172.16.9.1

glbp 10 priority 254

glbp 10 preempt delay minimum 60

glbp 10 weighting 110 lower 95 upper 105

glbp 10 weighting track 1 decrement 20

glbp 10 forwarder preempt delay minimum 20

All the PCs should be configured with 172.16.9.1 as the default gateway.

For futher reading refer to "Configuring GLBP"

http://www.cisco.com/en/US/products/ps6350/products_configuration_guide_chapter09186a008042fb97.html

Hope this helps! PLease use the rating system.

Regards, Martin

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