[Users] oVirt 3.4 - MTU Override not honoured by virtual NICs

[Jonas Israelsson]

I have a SAN Network defined in oVirt where I have enabled Jumbo frames 
(by setting the MTU to 9000).
Still I see now VM Nic;s attached to this network get MTU 1500 and are 
therefore basically not working.

I have created several VMs before all (still) have Jumbo Frames on the 
their san-interface, but newly created VMs get 1500.
Currently on 3.4 Beta2 (upgraded from alpha --> beta1 --->) and this 
behaviour have started somewhere along the way..

The host physical interface

em2       Link encap:Ethernet  HWaddr D0:67:E5:F9:2E:1C
           inet6 addr: fe80::d267:e5ff:fef9:2e1c/64 Scope:Link
           UP BROADCAST RUNNING MULTICAST  MTU:9000  Metric:1
           RX packets:503209263 errors:0 dropped:0 overruns:0 frame:0
           TX packets:483040537 errors:0 dropped:0 overruns:0 carrier:0
           collisions:0 txqueuelen:1000
           RX bytes:2395173035170 (2.1 TiB)  TX bytes:408352341106 
(380.3 GiB)


And on a VM

vnet25    Link encap:Ethernet  HWaddr FE:1A:4A:2F:D2:A3
           inet6 addr: fe80::fc1a:4aff:fe2f:d2a8/64 Scope:Link
           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
           RX packets:167 errors:0 dropped:0 overruns:0 frame:0
           TX packets:137 errors:0 dropped:0 overruns:0 carrier:0
           collisions:0 txqueuelen:500
           RX bytes:17662 (17.2 KiB)  TX bytes:26684 (26.0 KiB)

If manully setting the MTU everything work as expected.. (Until you 
reboot the machine)

Anyone else seen this ?

Rgds Jonas
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