What appropriate MTU size should be used in datacenter switches and routers? is there any standard or pros and cons?

Default is 1500 but that isn't enough to push data.

should we used 9000 MTU on all datacenter switches?

  • personally I think this is too broad because it will depend on so many specs and business needs. Personally I have seen that to avoid any bottlenecks admins do tend to max the MTU to avoid troubleshooting down the road this type of issues whether they are correlated or not. – DRP Feb 4 '18 at 1:46
  • What are the speeds on your server and switch interfaces? If they’re 10gb you should use jumbo frames. – Ron Trunk Feb 4 '18 at 1:46
  • we have mix network, 1G nic and 10G nic, we never/ever configured any server to use jumbo frame. our all server run on standard 1500 MTU. I raise this question because we are deploying new Datacenter so want to see what is the best practice for datacenter switches? we have all Cisco switches (99% nexus switches) – Satish Feb 4 '18 at 2:37

Jumbo frames are non-standard, so you are at the mercy of what your devices can do. For instance, some Cisco switches can do 9000 on some interfaces, but only 3000 on others. You need to make sure that you can use the same MTU all the way through, and that any hosts can use jumbo frames. Any traffic headed toward the Internet probably shouldn't use jumbo frames.

  • We have all Cisco switches and lets say my all switches support 9000 then should i configured all switch at MTU 9000 ? – Satish Feb 4 '18 at 2:34
  • Assuming all the traffic is local to your data center, and your servers can use 9000, then that should work just fine. Differing MTUs at layer-2 will break, and large packets will not work on the Internet. – Ron Maupin Feb 4 '18 at 2:37
  • I can understand L3 should be on 1500 MTU because its for outside world, but i here i am talking about L2 switches. – Satish Feb 4 '18 at 2:38
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    @Satish even though you change the mtu for network devices there wont be any effect if you dont change the hosts. – user36472 Feb 4 '18 at 3:35
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    @Satish you need to have all the links set to the same MTU. L2 will not fragment, and you don't want L3 to fragment because that puts a burden on the routers and the hosts. – Ron Maupin Feb 5 '18 at 15:27

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