Configuring WAN Links with EIGRP

EIGRP Support different WAN Links :
- Point to point links
- NBMA
o Multipoint Links
o Point to point links
EIGRP Uses up to 50 % of bandwith by default ;this bandwith utilization can be changed


Point to Point Links



Point to multipoint Links ( Hub & Spoke )





Bandwith utilization over point to point sub interfaces using Frame Relay :
Treats bandwith T1 as by default
Should Manually Configure bandwith as the CIR of the PVC

Bandwith utilization over multipoint frame relay,ATM and ISDN PRI
EIGRP used the physcal bandwith on the interface divided by the number of neighbors on that interface to calculate the bandwith attributed per neighbor
Each PVC can have different CIR,creating an EIGRP packet pacing problem
Multipoint interfaces :
Convert these to point to point configuration or manually configure bandwith by multiplying the lowest CIR by the number of PVC


Configuring EIGRP Bandwith use Across WAN Links




NB : From this picture we assumed there are 10 router which running EIGRP protocol in WAN Connections
So the bandwith calculated with this case is 1/10 of link capacity ( T1 interface as the default )
As described earlier ,the IP bandwith percent eigrp as number-percent commands allow the maximum percentage of bandwith of an interface that the EIGPR will be use
The circuits are provisioned 56 kbps links,but there is insufficient bandwith at the interface to support this allocation

For example if router C trying to communicate with all remote sites it will be need bandwith as 56 * 10 = 560 kbps,it exceed from the available bandwith 256 kbps
On each interface and subinterface,the EIGRP allocation percentage is raised to 110 percent of specified bandwith in an attempt to ensure that eigrp packet are delivered through the frame relay network
This adjustment cause EIGRP packet to receive approximately 28 kbps of the provisioned bandwith 56 Kbps on each circuit
This extra configuration restore 50:50 ration of delivery bandwith

EIGRP WAN Configuration : Hybrid Multipoint




This figure show us that there is link with a lower and higher connection
In point to point (router C) has a lower connection than other because it’s point to point connection
And the other ( point to multipoint ) the bandwith is shared equally among all circuits.
In this case the bandwith is set to 768 kbps,which is the sum of 3 CIR (256*3) = 768
Each link will be allocated one third of this bandwith,resulting 256 kbps each interface