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Cannot change br-int and br-tun MTU to >1500

we have a server setup where openstack components are KVM-VMs: 1. icehouse-controller. 2. icehouse-network. 3. icehouse-cinder.

All these components are attached to a bridge br-main-vm over subinterface (vlan 112) --> em2.112 of the main giga-ethernet interface em2. Thus, VM --> br-main-vm --> em2.112 --> em2. - All interfaces have mtu=9000 configured in the interfaces file. - Further each VM has its interface configures to mtu=9000. - Pinging and passing data can be performed with packet > 1500.

However, br-int and br-tun (GRE) MTUs cannot be configured. They have by default 1500. I tried the veth_mtu = 9000 in the [agent] section of ml2_conf.ini but in vain.

I do not want to reduce the guest VM MTU; thus, how to proceed.

Hint: I tried to change the MTU in: nano /sys/devices/virtual/net/br-tun/mtu and nano /sys/class/net/br-tun/mtu but it did not work, ovs rewrite them.

Regards Marwan

Cannot change br-int and br-tun MTU to >1500

we have a server setup where openstack components are KVM-VMs: 1. icehouse-controller. 2. icehouse-network. 3. KVM-VMs:

  1. icehouse-controller.

  2. icehouse-network.

  3. icehouse-cinder.

All these components are attached to a bridge br-main-vm over subinterface (vlan 112) --> em2.112 of the main giga-ethernet interface em2. em2.

Thus, VM --> br-main-vm --> em2.112 --> em2. em2.

 - All interfaces have mtu=9000 configured in the interfaces file.
   - Further each VM has its interface configures to mtu=9000.
   - Pinging and passing data can be performed with packet > 1500.

1500.

However, br-int and br-tun (GRE) MTUs cannot be configured. They have by default 1500. I tried the veth_mtu = 9000 in the [agent] section of ml2_conf.ini but in vain.

I do not want to reduce the guest VM MTU; thus, how to proceed.

Hint: I tried to change the MTU in: nano /sys/devices/virtual/net/br-tun/mtu and nano /sys/class/net/br-tun/mtu but it did not work, ovs rewrite them.

Regards Marwan