EIGRP

Answered Question
May 19th, 2007

EIGRP is hybrid routing protocol that uses characteristics of distance vector and link state technolgies.

I am not clear what distance vector technologies it use.

Can anyone help me to understand it?

Thanks,

Amolak

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Correct Answer by Richard Burts about 9 years 6 months ago

Amolak

Scott and Mohammed have provided interesting explanations of the distance vector concept. I would like to suggest an explanation from a slightly different perspective. In link state protocols a router originates advertisement of its links that are directly connected and passes along advertisements (LSAs) originated by other routers. So each link stat router knows exactly which router originated each advertisement (LSA). In diatance vector each router receives advertisements from its neighbors, applies the local metric, and then advertises to its neighbors all the routes in its own routing table. So a distance vector router sees all advertisements as being originated from its neighbors and does not know what router really originated the advertisement. And that is the operation of EIGRP, each router sees all advertisements as being originated from its neighbors.

HTH

Rick

Correct Answer by scottmac about 9 years 6 months ago

Distance Vector = "Hops"

EIGRP looks at the overall distace by generating a metric for the segment it sees added to the segment behind the next hop(s), if one exists.

The metrics are things like bandwidth & delay (primarily).

Here is a link to the onine version of Cisco's Internetworking Guide; it has some excellent explanations on the basics.

http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/index.htm

Good Luck

Scott

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Correct Answer
scottmac Sat, 05/19/2007 - 06:15

Distance Vector = "Hops"

EIGRP looks at the overall distace by generating a metric for the segment it sees added to the segment behind the next hop(s), if one exists.

The metrics are things like bandwidth & delay (primarily).

Here is a link to the onine version of Cisco's Internetworking Guide; it has some excellent explanations on the basics.

http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/index.htm

Good Luck

Scott

mohammedmahmoud Sat, 05/19/2007 - 07:03

Hi,

The name distance vector is derived from the fact that routes are advertised as vectors of (distance, direction), where distance is defined in terms of a metric and direction is defined in terms of the next-hop router.

Distance = Metric

Vector = Next-hop

While the name link state is derived from the fact that each router advertises the states of its links (plus information about itself and the directly connected neighbors).

And its obvious that EIGRP uses the distance vector technology when advertising routes to its neighbors.

HTH, please do rate all helpful replies,

Mohammed Mahmoud.

Correct Answer
Richard Burts Sat, 05/19/2007 - 17:39

Amolak

Scott and Mohammed have provided interesting explanations of the distance vector concept. I would like to suggest an explanation from a slightly different perspective. In link state protocols a router originates advertisement of its links that are directly connected and passes along advertisements (LSAs) originated by other routers. So each link stat router knows exactly which router originated each advertisement (LSA). In diatance vector each router receives advertisements from its neighbors, applies the local metric, and then advertises to its neighbors all the routes in its own routing table. So a distance vector router sees all advertisements as being originated from its neighbors and does not know what router really originated the advertisement. And that is the operation of EIGRP, each router sees all advertisements as being originated from its neighbors.

HTH

Rick

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