eigrp bandwidth

[carl_townshend]

Hi all, what will happen if I dont configure this command under my interfaces when using eigrp, and do any of the other protocols need this command ?

[asanemeterio]

Hi Carl,

Bandwidth is an important parameter to route path calculation. See these documents for more

http://www.cisco.com/en/US/partner/tech/tk1330/tsd_technology_support_technical_reference_chapter09186a008075970b.html

and

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

Good luck

[ruwhite]

EIGRP will pull the bandwidth from the default bandwidth for the interface type. There's no good list of these that I know of. :-(

OSPF bases it's default metric on the bandwidth of the interface, as well. IS-IS and RIP use fixed metrics no matter what the link type is, or the bandwidth.

:-)

Russ

[m-haddad]

Hello,

Not adding the bandwidth command would let the EIGRP use the default interface bandwidth. However, this is not a problem is usually you have one link to same site. When you have multiple routes to certain sites you usually use the bandwidth to affect the routing decision of the EIGRP.

For example if you have a main site connected to a branch site using to Serial links will lead the EIGRP to load-balance over the two links. However, your serial maybe of different bandwidth for example one with 64Kbps and the other is 2Mbps. To affect the EIGRP routing decision you can issue the command bandiwdth 2000 on the Serial and then EIGRP will install one route to the branch office.

All other protocols behave the same however, OSPF also base it's metric on other values like delay and reliability etc...

Hope this explains your question,

Appreciate your rating,

Regards,

[ruwhite]

"To affect the EIGRP routing decision you can issue the command bandiwdth 2000 on the Serial and then EIGRP will install one route to the branch office."

In general, we prefer that you set the bandwidth to what the bandwidth really is, as much as possible, and use delay to traffic engineer. This is because EIGRP also determines how fast to send packets on links under T1 in speed.

"All other protocols behave the same however, OSPF also base it's metric on other values like delay and reliability etc... "

OSPF only uses the bandwidth, not the delay, etc.

:-)

Russ

[m-haddad]

Russ,

Totally agree with you on point 1. As for point 2 I got confused between EIGRP and OSPF because yesterday was doing some reading on "metric weights" of EIGRP. ;-)

Thanks for the correction,

Regards,

[ruwhite]

I am perpetually confused by OSPF, so don't worry. :-)

:-)

Russ