Worth reading this on choosing MTU on transit link. http://blog.apnic.net/2014/12/15/ip-mtu-and-tcp-mss-missmatch-an-evil-for-network-performance/
-Sad >> >> On Fri, Jul 22, 2016 at 10:01 PM, Baldur Norddahl < >> baldur.nordd...@gmail.com> wrote: >> >>> Hi >>> >>> What is best practice regarding choosing MTU on transit links? >>> >>> Until now we have used the default of 1500 bytes. I now have a project >>> were >>> we peer directly with another small ISP. However we need a backup so we >>> figured a GRE tunnel on a common IP transit carrier would work. We want >>> to >>> avoid the troubles you get by having an effective MTU smaller than 1500 >>> inside the tunnel, so the IP transit carrier agreed to configure a MTU of >>> 9216. >>> >>> Obviously I only need to increase my MTU by the size of the GRE header. >>> But >>> I am thinking is there any reason not to go all in and ask every peer to >>> go >>> to whatever max MTU they can support? My own equipment will do MTU of >>> 9600 >>> bytes. >>> >>> On the other hand, none of my customers will see any actual difference >>> because they are end users with CPE equipment that expects a 1500 byte >>> MTU. >>> Trying to deliver jumbo frames to the end users is probably going to end >>> badly. >>> >>> Regards, >>> >>> Baldur >>> >> >> >