GLBP loadbalancing & IPT

Unanswered Question
Aug 28th, 2007
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Is there a preferred glbp load balancing algorithm (round-robin, host-dependant,..) to use with IP Telephony (where GLBP is providing the default gateway for the IP phone).



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GLBP works by making use of a single virtual IP address, which is configured as the default gateway on the hosts. The different routers that assume the forwarding role use different virtual MAC addresses for the same virtual IP address to which packets are forwarded by the hosts.

There are two types of routers in a GLBP group which make redundancy and load balancing work. From the group of routers configured in a GLBP group, there is one router elected as the Active Virtual Gateway (AVG) which assigns a virtual MAC address to each member of the GLBP group. The members which assume responsibility for forwarding packets sent to the virtual MAC address assigned to it by the AVG are known as Active Virtual Forwarders (AVFs) for the group. The AVG responds to Address Resolution Protocol (ARP) requests generated by the hosts for the virtual IP address. Load sharing is achieved by the AVG replying to the ARP requests with different virtual MAC addresses for the same virtual IP address. There are mechanisms built in GLBP for other routers in the group to take over if the AVG or AVFs for a group fail.


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