Ceph + MTU 9000

[MateuszK]

Hello,

I am experiencing an issue with configuring the MTU for the interface used by Ceph. When I set the MTU to 9000 on both the server interface and the physical switch, I can successfully ping with a maximum packet size of 8958. However, I am unable to access resources in the Ceph cluster.

On the other hand, when I set the MTU to 8000 on the server, the maximum ping size is 7972, and the Ceph cluster works correctly.

What could be causing Ceph to fail when using MTU 9000?

 

[aaron]

I can successfully ping with a maximum packet size of 8958

Well, it should be 8972 bytes of payload that should work. Seems like something else in the network might not be able to handle larger payloads. Are you in a VLAN? Maybe some other layers in the infrastructure that you don't control or know about that might add additional headers, pushing the packets to a size too large to be transported?