Interface Speed and Bandwith

Hi all, hope all is well, I have a question, ig i change the speed and bandwidth on a 1 gigabit interface to speed of 100 and bandwidth 100, will this interface be equivalent to a Fast ethernet interface (100mb)?

Thank you for the help in advance.

Hello Sidney

The speed command will change the actual operational bandwidth of the interface. For Ethernet interfaces, the only options you have for speed are 10 Mbps, 100 Mbps, 1000 Mbps, and for interfaces capable of higher speeds, you may also have 10Gbps, 25Gbps, 40Gbps, 100Gbps, and so on. So the speed command will only allow you to configure specific speeds, those that the interface is capable of operating at.

The bandwidth command is different. Changing this value will not affect the actual bandwidth of the interface. It actually acts as a label on the interface and is used to determine the cost and metric of routes when using routing protocols such as EIGRP or OSPF. You are able to configure any bandwidth value with the given range of the command. This value should only be changed if you want to influence routing performed by a routing protocol, in some manner.

I hope this has been helpful!

Laz

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Hi @lagapides, thank you for your response, this answers and clarifies my question. Thank you.

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We have applied for 10 mb mpls link, provider has hard coded the negotiation and set to speed 10 full duplex, so at our end also we need to hard code to 10 full duplex. is it correct ? Ideally in my understanding, Speed should be 100 with full duplex. Provider can cap the speed at PE end with rate limit etc. please suggest if this is correct to set speed 10 and duplex full, will it impact when it come to production ? or should get it changed to speed 100 with full deuplex ? Expecting quick reply on this, thanks for your clarification as always.

Hello Ravi

It all depends on what layer 2 technology the service provider is delivering to your premises, and what they have configured on their end.

Is it an Ethernet connection, and they’re running MPLS over that? If so, and if they have configured 10 Mbps on their end, then yes, you must do the same on your end. That’s simply how Ethernet works. You would apply this independent of what technology is running on top of that. If there is a speed mismatch, the link will simply not come up. The speed must match on both ends regardless of all other parameters.

Now if the provider is delivering the 10 Mbps in a different manner, say using rate limiting, as you mention, then the speed on the interface has nothing to do with that. The provider may be giving you a GigabitEthernet interface, and rate limit it to 10Mbps, the result would be the same.

So on your end, you should set the speed and duplex to whatever is configured on the provider end. Otherwise, the link will not function.

I hope this has been helpful!

Laz