Sunday, 7 August 2016

Gateway Load Balancing Protocol (GLBP)

1 Gateway load balancing protocol (GLBP)

è       It also cisco proprietary protocol. Same like as HSRP but the terminology is different and the behaviour is much more dynamic.

è      Instead of having just one active performing forwarding for the virtual router address, all routers in the group can participate and offer load balancing by forwarding a portion of overall traffic.
è    One router is elected the active virtual gateway (AVG). it have highest priority value or Highest ip address in the group.
Priority : 1 to 255 and default 100
Group: 0 to 1023
GLBP priority:
Switch(Config)#glbp <group> priority <level>

è       AVG also assigns the necessary virtual MAC addresses to each of the routers participate in the GLBP group. Up to four virtual mac address can be used in group. Each of these routers is referred as an active virtual forwarder (AVF) and other router in the group serve as backup or secondary virtual forwarders, in case the AVF fails. The AVG also assign secondary roles.

è     In HSRP, another router cannot take over an active role until the current active router fails. GLBP does allow a router to preempt and become the AVG if it has a highest priority than the current AVG. Use the following command to enable pre-empting and to set a time delay before pre-empting begins:
Switch(Config-if)#glbp <group> preempt <delay minimum second>

è      Hello message are sent at hello time intervals, with a default 3 second and hold-down timer is 10 second. We can adjust the GLBP timers:
Switch(Config-if)#glbp <group> timers msec <hellotime> msec <holdtime>
Hello timer: 1 to 60 second means 50 to 60000 millisecond
Hold timer:  up to 180 second means 180000 millisecond

è        Each router participating in the GLBP group can become an AVF, if the AVG assigns it that role, along with a virtual MAC address. The virtual MAC address always have the form 0007.b4xx.xxyy. The xx.xx represents six 0 bits followed by a 10 bit GLBP group number and the 8 – bit yy value is the virtual forwarder number.

è         Enable GLBP
To enable GLBP, to assign a virtual IP address to the group by using the following to define the method:
Switch(config-if)# glbp <group> ip <ip-address>

è      GLBP Load balancing
The AVG establishes load balancing by handling out virtual router MAC addresses to clients in a deterministic fashion. Naturally, the AVG first must inform the AVFs  in the group of the virtual MAC address that each should use.
Load-balancing method:
1.       Round-Robin
2.       Weighted
3.       Host dependent
Switch(config-fi)#glbp <group> load-balancing <round-robin/weighted/host-dependent>

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