Should Bandwidth match between Routers?

JoshGarmonCiscoCCNA · ‎10-07-2015

Should bandwidth match between every two router interfaces connected to each other?

And BANDWIDTH is NOT the same as the "fastEthernet, GigabitEthernet, etc..." funtionality correct?

Mark Malone · ‎10-07-2015

the bandwidth statement is for IGP protocols such as eigrp or ospf , they use them to calculate the metric of the best path for your traffic so yes your right it is irrespective of the physical speed of the interface but is highly recommended due to the fact it calculates metrics and as well you may have issue with tcp packets if its not set to the line speed that you actually have i.e 20mb ISP circuit so you set your bandwidth to 20000 , if the links are the links are point to point then the statements would match but in the real world they hardly ever are , so could be different at either end

JoshGarmonCiscoCCNA · ‎10-07-2015

thanks Mark!

trfinkenstadt · ‎10-07-2015

To add on to Mark's answer, QoS also relies on the bandwidth statements, especially if you are using the "bandwidth percent" and/or the "bandwidth remaining percent" structures.

saif musa · ‎10-07-2015

Addition to mark and trifink valuable posts, the value you configure with the bandwidth command is not what is displayed by the show interface command. The value you configure is that to be used in IGRP updates and also used in computing load.

Dan Lukes · ‎10-08-2015

You are asking in community with no relationship to the topic. You are lucky as other CSC member has answered despite of it. Unfortunately, their time will be wasted if future users with same question will not find the answer.

So please use blue [ EDIT ] button to move this thread to Network Infrastructure -> Other Network Infrastructure Subjects

Also, consider rating of valuable answers. It's way to say "thank you for your valuable response". And it will help others to find valuable answers.

Thank you.

Masoud Pourshabanian · ‎10-08-2015

Hello,

Cisco switches and routers and many other devices use auto-negotiation on each interface. When you connect two devices, both devices on each link send auto negotiation messages to each other to match their speeds. They finally work with the highest speed that both match. For example, if you connect a 10/100 interface to a 10/100/1000 interface, they will agree on100.

Bandwidth command does not have anything to do with interface speed. It is used by routing protocols to find the best path.

Hope it helps,

Masoud

JoshGarmonCiscoCCNA · ‎10-08-2015

thanks Masoud!

Masoud Pourshabanian · ‎10-08-2015

You are most welcome.