EIGRP(bandwidth / clockrate )?

arsalan921arsalan921 Member Posts: 56 ■■□□□□□□□□
Hello All,

I have a question regarding EIGRP WAN connections.

EIGRP can support point-to-point and NBMA ( multipoint and point-to-point )...

now i am studying self-study guide of bsci, and in one example where there is a hub and spoke design used.

1 central site and 10 remote sites.

bandwidth available on central site link = 256 kbps.

CIR in each of the remote sites = 56kbps and BW in each of remote site= 25kbps

now in example he has made 10 point-to-point connections on the central site router, on every subinterface he has set the bandwidth to 25kbps and ip bandwidth-percent eigrp 63 110 and eactly same configuration is done on ever remote router.

1st question is why this bandwidth percentage is set to 110 ? default it is 50%. how can eigrp use more than the actual bandwidth available ( for its routing purpose ). what i understand is that if you set this to 100, then all the bandwidth will be used for eigrp routing ( not left with any data communication ) and he has set to 110 ? so how will other data be transferred ?

2nd question. cir at remote site is shown 56 kbps but bandwidth is 25kbps. and the clock rate would also be set to 25 kbps , so how can we say that cir is 56 , because cir means that this is the least you get,

last question is a confirmation ? i just want to make sure that we have to use the clock rate command here to ? setting the bandwidth equal to 25 doesnt make any difference until clock rate is also set ? because setting the bandwidth to 25 will be used for eigrp metric calculation and for other documentation purposes but the router will not be clocking at this speed until the clock rate is also set to 25000 (bps) ? am i right ?

thank you


  • WRKNonCCNPWRKNonCCNP Member Posts: 38 ■■□□□□□□□□
    When using EIGRP, the bandwidth command is used for metric calculations, but does not have any effect on the actual speed of the interface. In conjunction with the 'bandwidth 25' on an interface, the 'ip bandwidth-percent eigrp 63 110' would allow eigrp to use 27.5 kbps of the interface bandwidth. The bandwidth-percent command percentage is based on the bandwidth defined by the 'bandwidth' command.

    CIR = committed information rate, which defines how much you can send on that link given a certain timeframe, but it doesn't necessarily go with the line rate. You could have a t1 link with a cir of 56kbps. The bandwidth command specifying 25kbps only tells EIGRP what to use for metric calculation, but doesn't control the actual available bandwidth of the link. You are not required to set the clock rate on an interface to match the value used in the bandwidth command.
  • arsalan921arsalan921 Member Posts: 56 ■■□□□□□□□□
    thank you man,
    it has cleared my concept
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