Red Hat Bugzilla – Bug 873745
3.2 when removing a non bridged network from an interface the MTU is not updated to reflect the correct MTU
Last modified: 2016-02-10 14:53:14 EST
Created attachment 639417 [details]
Description of problem:
When there is interface with high MTU like 9000 and from webadmin we attach VLAN network to that interface with lower MTU like 5000 the physical interface MTU will stay at 9000. Only the VLAN will be at 5000 MTU.
Version-Release number of selected component (if applicable):
Steps to Reproduce:
1.Create nonvm (bridgeless) network with MTU 9000 and attach it to the eth1 host
2.create vm-vlan network with MTU 5000
3.Open SetupNetworks > detach nonvm-mtu9000 from the interface and attach vm-vlan-mtu5000 to eth1.
eth1 have MTU 9000
eth1 should have MTU 5000
The bug is that when removing a non-bridged network we need to update the MTU on the interface to be the new maximum between all networks left attached to the interface.
This logic also applies for bridged network.
If no network is attached to the interface we need to remove the MTU property from the device.
Found another scenario:
1. Create network vm-mtu-5000 and attache it to eth1 on the host > apply.
2. Create network vm-mtu-1500.
3. Detach network vm-mtu-5000 from eth1 on the host and attach network vm-mtu-1500 to eth1 on the host > apply.
The MTU on eth1 still have MTU 5000 and should be 1500
grep MTU /etc/sysconfig/network-scripts/ifcfg-*
Created attachment 669568 [details]
vdsm.log - for scenario from comment 4
Verified on vdsm-4.10.2-3.0.el6ev.x86_64.
test both scenarios.
MTU was update as it should.
3.2 has been released