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AVG and VF in GLBP...

hello,,,

In GLBP...AVG router will have both role of AVG and VF??? and i am having some confusion with Redirect time in GLBP so please help me to clear that fundamental....

regards

Devang

3 REPLIES

Re: AVG and VF in GLBP...

Hi Devang,

AVG: this router i having functionlike redundancy and also provide the virtual MAC address right

Members of a GLBP group elect one gateway to be the active virtual gateway (AVG) for that group. Other group members provide backup for the AVG in the event that the AVG becomes unavailable. The AVG assigns a virtual MAC address to each member of the GLBP group

VF: in GLBP group all router with the virtual MAC address is known as the VF..right...

Each gateway assumes responsibility for forwarding packets sent to the virtual MAC address assigned to it by the AVG. These gateways are known as active virtual forwarders (AVFs) for their virtual MAC address

Redirect Timer & Timeout Interval & Secondary Holdtime

A virtual forwarder that is assigned a virtual MAC address by the AVG is known as a primary virtual forwarder. If the virtual forwarder has learned the virtual MAC address from hello messages, it is referred to as a secondary virtual forwarder.

The redirect timer sets the time delay between a forwarder failing on the network and the AVG assuming that the forwarder will not return. The virtual MAC address that the forwarder was responsible for replying to is still given out in Address Resolution Protocol (ARP) replies, but the forwarding task is handled by another router in the GLBP group. You can also take it as the redirect time is the interval during which the AVG continues to redirect hosts to the old virtual forwarder MAC address. When the redirect time expires, the AVG stops redirecting hosts to the virtual forwarder, although the virtual forwarder will continue to forward packets that were sent to the old virtual forwarder MAC address

The timeout interval is the time delay between a forwarder failing on the network and the MAC address for which the forwarder was responsible becoming inactive on all of the routers in the GLBP group. After the timeout interval, packets sent to this virtual MAC address will be lost. The timeout interval must be long enough to allow all hosts to refresh their ARP cache entry that contained the virtual MAC address.

The secondary holdtime is the interval during which the virtual forwarder is valid. When the secondary holdtime expires, the virtual forwarder is removed from all gateways in the GLBP group. The expired virtual forwarder number becomes eligible for reassignment by the AVG.

HTH, if yes please rate the post.

Ankur

Re: AVG and VF in GLBP...

thanks Mr. Ankur,,,

it means redirect time tell AVG, the VF which is courrently down will not be return...so assume it is as down...right...

regards

Devang

Re: AVG and VF in GLBP...

Hi Devang,

For the time period of redirect timer AVG will redirect hosts to the virtual forwarder but as and when redirect timer expire the AVG stops redirecting hosts to the virtual forwarder.

It will come to know that VF is currently down and will not return and this will happen because AVG already waited for the expiration of redirect timer.

HTH, if yes please rate all post.

Ankur

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