Why would use MTU??

[Tigerjoe]

Why would someone want to use MTU over an interface? What is the reason for limiting packet size? Wouldnt this put more overhead on the router and cause network traffic to slow down or even drop packets that cant be fragmented?




T J

To PING or not to PING?

 

[hexn]

Ideally, you want the MTU to be the same as the smallest MTU of all the networks between your machine and a message's final destination. Otherwise, if your messages are larger than one of the intervening MTUs, they will get broken up (fragmented), which slows down transmission speeds.

Trial and error is the only sure way of finding the optimal MTU, but there are some guidelines that can help. For example, the MTU of many PPP connections is 576, so if you connect to the Internet via PPP, you might want to set your machine's MTU to 576 too. Most Ethernet networks, on the other hand, have an MTU of 1500, which is the default MTU setting for Windows 95.

 

[Tigerjoe]

Makes sense. I was thinking 1500 was default for ethernet and wan networks.

Thanks T J

To PING or not to PING?

 

[NewbieGirl]

How do you configure the MTU on a cisco router?
Thanks,
Danielle

 

[Tigerjoe]

Router(config)#in s1
Router(config-if)#mtu ?
<64-18000> MTU size in bytes

or to set mtu per protocol,

Router(config-if)#ip mtu ?
<68-1000000> MTU (bytes)




T J

To PING or not to PING?