EIGRP aggregate traffic

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Sep 18th, 2008
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Hi,

BSCI Exam Certification Guide,4th Ed. mentions "EIGRP aggregate traffic..." (see bottom of page 103). What does it mean by that? Does it mean EIGRP traffic that goes through an interface from/to all configured VCs?

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Giuseppe Larosa Fri, 09/19/2008 - 02:28
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Hello Wassim,

may you report the whole sentence so that can help to understand the meaning.


In NBMA you can have scenarios where the access link is oversubscribed at the hub site and so it is important to control the amount of traffic EIGRP will send out in case of a topology change.

Control of traffic is important because EIGRP relies on a diffusive algorithm and a query is sent out to each neighbor when the best route fails and no feasible successor is available. the router that sends the query waits for an answer from each EIGRP neighbor until the expiration of timer: neighbors that don't answer timely are resetted.


Hope to help

Giuseppe



ccnpninja Fri, 09/19/2008 - 12:43
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Here's the excerpt from the aforementioned book:

"Cisco identifies three rules that you should follow when configuring EIGRP over an NBMA cloud:

■ EIGRP traffic should not exceed the committed information rate (CIR) capacity of the virtual

circuit (VC).

■ EIGRP aggregated traffic over all the VCs should not exceed the access line speed of the

interface.

■ The bandwidth allocated to EIGRP on each VC must be the same in both directions."

Giuseppe Larosa Fri, 09/19/2008 - 13:06
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Hello Wassim,

here EIGRP aggregated traffic over all the VCs has to be less then the access line speed otherwise some packet can be lost, causing at least the need for retransmission of it, and suboptimal EIGRP performance, and in case of heavy oversubscription EIGRP instability after a topology change as I tried to explain in the previus post.


Actually a query packet is acknowledged by the receiver if no EIGRP ACk is received the router will transmit the query again, I'm not sure that the SIA timer is reset in this case.



Hope to help

Giuseppe


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