Do I need to change MTU from 1500 to 9000 on my 10Gb switch?

[ratha chum]

Hi,

I am using 10G switch to Server with 10G interface card. Do I need to change default MTU from 1500 to 9000 to support max bandwidth like iSCSI?

Thanks.

[marce1000 · Accepted solution]

 - Only if  you effectively have iscsi ; here are some threads to review on the subject :

      https://community.cisco.com/t5/switching/switch-uplink-port-mtu/td-p/3081201

      https://community.cisco.com/t5/switching/ramifications-of-setting-mtu-9000/td-p/2594745

      https://community.cisco.com/t5/switching/10gb-port-jumbo-frames/td-p/2880146

 M.

[Edward Clear]

Short Answer: It will help, but be careful.

It will help, because your are improving the ratio of overhead to payload in each packet.  So more of your 10G B/W is used for payload.  In ye olden days, this would also be more efficient at the receiving hosts as you'd get less interrupts for a given amount of data.   But interrupt coalescing and TCP Offload have muted that point.

The "be careful" is that you should make sure that all hosts and routers on any jumbo frame subnet support and are configured (both L2 and L3) for the same jumbo MTU.  Otherwise you can have packets dropped.    If your servers and clients are on different subnets, you need to make sure the Path MTU supports it, otherwise the change will be ineffective.