[SOLVED] Jumbo Frames for an UCS Guest?

[pixel24]

Hi@all,

i want to enable jumbo frames (MTU=9000) on a PVE guest (Univention UCS 5.0.3).the guest is "hanging" on vmbr0:

vmbr0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether a0:36:9f:4c:3b:ee brd ff:ff:ff:ff:ff:ff
inet 192.168.xx.1/24 brd 192.168.83.255 scope global vmbr0
valid_lft forever preferred_lft forever
inet6 fe80::a236:9fff:fe4c:3bee/64 scope link 
valid_lft forever preferred_lft forever

This is the bridge for the LAN. The physical interface (NIC) that is bound to the vmbr0:

ens1f1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq master vmbr0 state UP group default qlen 1000
    link/ether a0:36:9f:4c:3b:ee brd ff:ff:ff:ff:ff:f

In the VM (UCS) I see:

ens18: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
    link/ether 5a:65:eb:28:35:be brd ff:ff:ff:ff:ff:ff
    inet 192.168.xx.5/24 brd 192.168.83.255 scope global ens18
       valid_lft forever preferred_lft forever
    inet6 fe80::5865:ebff:fe28:35be/64 scope link
       valid_lft forever preferred_lft forever

Where do I have to set "mtu=9000" everywhere? In the physical PVE device?, at the vmbr0?, in the UCS? or at all?

with best
pixel24

 

[aaron]

On the PVE host, try to set the MTU at the vmbr0, then check the ip a output again after applying the config. The MTU should be pushed down to the phyiscal device.

You will also have to set it within the guest AND on your whole network, switches, routers, other clients and so on.

 

[pixel24]

Worked. Thanks a lot!