Bandwidth Command on Interface

[rdotson]

I have several routers connected to an ISP.  The physical connection speed in one instance is 1gb/s, but ISP rate limits the bandwidth to 200 mb/s.  I have another that is physically connect at 10gb/s but is rate limited to 4gb/s.

Should the bandwidth statements be changed to match the rate limited bandwidth for EIGRP to function properly?

Also if the command is kb/s should a 1 gb/s circuit be set to 1000000 or 1048576?

[Joseph W. Doherty · Accepted solution]

As a general rule, I suggest setting the bandwidth statement to reflect available bandwidth, but cannot recall whether EIGRP uses it as part of its normal path metric calculation.  (I recall EIGRP "likes" to use delay.  Likely someone will post the answer.)

As to your second question, for gig, I would suggest just using 1000000.

[actciscocco]

I'm assuming this is a multipoint configuration. According to what I've experienced lately with ISR44xx and from what I'm reading, setting different bandwidth values for each link on a multipoint WAN connection causes timing issues. Most of my links are 250 Mbps, except for two that are 100 Mbps. The two that are 100 Mb are timing out in their relationships with the ones that are 250 Mb, and the ones that are 250 sometimes time out with the ones that are 100 but not with others that are 250 Mb.

Reading revealed that it's most likely due to difference in timers due to different CIRs at each site. It looks like in order to get the most stable configuration of all I need to set each site to the lowest common CIR for all sites, which would be 100,000.

Can anyone confirm or deny that such a situation (different link speeds across a WAN) causes these problems, and whether lowering the bandwidth to be the same for all sites will fix it?

Thanks.

[lpassmore · Accepted solution]

Using the default configuration, EIGRP will use bandwidth and delay as the metrics.  in my mind, you should always use the true throughput for the bandwidth values, but as long as you get the ratio correct it won't really matter too much.  Unless you use such small values that delay starts to figure into the equation.  I would use 200000 as the bandwidth on the ISP link and 4000000 for the physical link.  

[rdotson]

Thanks all for your responses.

[mithun_raam]

EIGRP uses Bandwidth and Delay For Accurate cost calculation and efficient route selection. you must use 200,000 kbps for ISP1 and 4,000,000.

Just in curious, why do you want to run EIGRP on Untrust networks ?