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Message #39948
[Bug 1443607] Re: Linux Bridge: can't change the VM's bridge and tap interface MTU at Compute node.
** Also affects: neutron/kilo
Importance: Undecided
Status: New
** Changed in: neutron/kilo
Status: New => Fix Committed
** Changed in: neutron/kilo
Milestone: None => 2015.1.2
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https://bugs.launchpad.net/bugs/1443607
Title:
Linux Bridge: can't change the VM's bridge and tap interface MTU at
Compute node.
Status in networking-cisco:
New
Status in neutron:
Fix Released
Status in neutron kilo series:
Fix Committed
Bug description:
I use DevStack to deploy OpenStack with Linux Bridge instead of OVS in
a multi-node set up.
I¹m testing jumbo frames and want to set MTU to 9000.
At the Network node, the bridges and tap interfaces are created with
MTU = 9000:
localadmin@qa4:~/devstack$ brctl show
bridge name bridge id STP enabled interfaces
brq09047ecb-1c 8000.7c69f62c4f2f no eth1
tapedbcd5b1-a6
brq319688ab-93 8000.3234d6ee3a18 no bond0.300
tap4e230a86-cb
tapfddaf12e-85
virbr0 8000.000000000000 yes
localadmin@qa4:~/devstack$ ifconfig brq09047ecb-1c
brq09047ecb-1c Link encap:Ethernet HWaddr 7c:69:f6:2c:4f:2f
inet6 addr: fe80::3c79:c8ff:fe23:2fe7/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:9000 Metric:1
RX packets:696 errors:0 dropped:0 overruns:0 frame:0
TX packets:8 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:30617 (30.6 KB) TX bytes:648 (648.0 B)
localadmin@qa4:~/devstack$ ifconfig brq319688ab-93
brq319688ab-93 Link encap:Ethernet HWaddr 32:34:d6:ee:3a:18
inet6 addr: fe80::e0ec:3bff:fe09:4318/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:9000 Metric:1
RX packets:30 errors:0 dropped:0 overruns:0 frame:0
TX packets:8 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:4236 (4.2 KB) TX bytes:648 (648.0 B)
localadmin@qa4:~/devstack$ ifconfig tapedbcd5b1-a6
tapedbcd5b1-a6 Link encap:Ethernet HWaddr ae:fb:64:53:f7:2d
inet6 addr: fe80::acfb:64ff:fe53:f72d/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:9000 Metric:1
RX packets:65 errors:0 dropped:0 overruns:0 frame:0
TX packets:947 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:10223 (10.2 KB) TX bytes:80510 (80.5 KB)
localadmin@qa4:~/devstack$ ifconfig tap4e230a86-cb
tap4e230a86-cb Link encap:Ethernet HWaddr 32:34:d6:ee:3a:18
inet6 addr: fe80::3034:d6ff:feee:3a18/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:9000 Metric:1
RX packets:2073 errors:0 dropped:0 overruns:0 frame:0
TX packets:2229 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:8878139 (8.8 MB) TX bytes:8914532 (8.9 MB)
localadmin@qa4:~/devstack$ ifconfig tapfddaf12e-85
tapfddaf12e-85 Link encap:Ethernet HWaddr d2:33:29:9b:2c:e8
inet6 addr: fe80::d033:29ff:fe9b:2ce8/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:9000 Metric:1
RX packets:152 errors:0 dropped:0 overruns:0 frame:0
TX packets:295 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:15237 (15.2 KB) TX bytes:51849 (51.8 KB)
The instance launched at the Compute node has interface eth0 MTU =
9000:
ubuntu@qa5-vm2:~$ ifconfig
eth0 Link encap:Ethernet HWaddr fa:16:3e:05:36:58
inet addr:10.0.0.4 Bcast:10.0.0.255 Mask:255.255.255.0
inet6 addr: fe80::f816:3eff:fe05:3658/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:9000 Metric:1
RX packets:1169 errors:0 dropped:0 overruns:0 frame:0
TX packets:384 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:1408206 (1.4 MB) TX bytes:1336535 (1.3 MB)
However, the associated bridge and tap interface MTU is set to default 1500:
localadmin@qa5:~/devstack$ brctl show
bridge name bridge id STP enabled interfaces
brq319688ab-93 8000.6805ca302558 no bond0.300
tapa7acee8a-54
virbr08000.000000000000 yes
localadmin@qa5:~/devstack$ ifconfig brq319688ab-93
brq319688ab-93 Link encap:Ethernet HWaddr 68:05:ca:30:25:58
inet6 addr: fe80::a8ef:dfff:feb1:8eec/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:162 errors:0 dropped:0 overruns:0 frame:0
TX packets:8 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:910353 (910.3 KB) TX bytes:648 (648.0 B)
localadmin@qa5:~/devstack$ ifconfig tapa7acee8a-54
tapa7acee8a-54 Link encap:Ethernet HWaddr fe:16:3e:05:36:58
inet6 addr: fe80::fc16:3eff:fe05:3658/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:395 errors:0 dropped:0 overruns:0 frame:0
TX packets:1180 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:500
RX bytes:1338757 (1.3 MB) TX bytes:1408932 (1.4 MB)
localadmin@qa5:~/devstack$ ifconfig bond0.300
bond0.300 Link encap:Ethernet HWaddr 68:05:ca:30:25:58
inet6 addr: fe80::6a05:caff:fe30:2558/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:9000 Metric:1
RX packets:11507 errors:0 dropped:0 overruns:0 frame:0
TX packets:11590 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:14831272 (14.8 MB) TX bytes:14943870 (14.9 MB)
As a result, jumbo frames are fragmented coming out from the Compute node.
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