MTU Increase

[JosephPhilip1]

I am Planning to configure jumbo frames on the external router connecting with our ISP. The ISP will also set 9000 MTU on their end But If I make an MTU increase on the external router will it affect the firewall connected to the router. The firewall is set to 1500 MTU.

[nazimkha]

Whats the use of having MTU as 9000 on WAN when your internal network (firewall) is set to 1500

[JosephPhilip1]

We are doing a network upgrade in next 3 months which requires jumbo frames

[Patrick.Williams]

The key concept about jumbo frames or "Baby Giants" as i often call it, is to keep in mind that all the network devices along the communication path must support jumbo frames. Jumbo frames is required  to be configured to work on the ingress and egress interfaces of each device along the end-to-end transmission path.

Also all of your devices within your  topology must also agree on the maximum jumbo frame size it will handle. If there are devices within the network path that for some reason has  varying frame sizes( One Side 1500 the other 9000), in most cases you will end up with fragmentation problems.

If your firewall remains at 1500MTU within the  path and receives a jumbo frame, it will simply drop it.

So implement your Jumbo Frames similar to the diagram listed.

Cheers

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