I'm running an undercloud in OVB which requires that we set the system mtu to 1400. It appears that the br-int, ovs-system and docker0 interfaces get created with MTU's greater than 1400. I noticed a series of entries in the log about dropped packets:
[240767.446990] br-ctlplane: dropped over-mtu packet: 1500 > 1400
[241367.431466] br-ctlplane: dropped over-mtu packet: 1500 > 1400
[241967.415423] br-ctlplane: dropped over-mtu packet: 1500 > 1400
[242567.500707] br-ctlplane: dropped over-mtu packet: 1500 > 1400
[243167.513946] br-ctlplane: dropped over-mtu packet: 1500 > 1400
[243767.411584] br-ctlplane: dropped over-mtu packet: 1500 > 1400
[244367.402542] br-ctlplane: dropped over-mtu packet: 1500 > 1400
[244967.433133] br-ctlplane: dropped over-mtu packet: 1500 > 1400
Here's my interface list:
[centos@undercloud ~]$ ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN qlen 1
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1400 qdisc pfifo_fast state UP qlen 1000
link/ether fa:16:3e:76:99:aa brd ff:ff:ff:ff:ff:ff
inet 192.168.103.231/22 brd 192.168.103.255 scope global dynamic eth0
valid_lft 55460sec preferred_lft 55460sec
inet6 fe80::f816:3eff:fe76:99aa/64 scope link
valid_lft forever preferred_lft forever
3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1400 qdisc pfifo_fast master ovs-system state UP qlen 1000
link/ether fa:16:3e:6c:9c:99 brd ff:ff:ff:ff:ff:ff
inet6 fe80::f816:3eff:fe6c:9c99/64 scope link
valid_lft forever preferred_lft forever
4: ovs-system: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN qlen 1000
link/ether 72:a1:03:9c:92:14 brd ff:ff:ff:ff:ff:ff
5: br-ctlplane: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1400 qdisc noqueue state UNKNOWN qlen 1000
link/ether fa:16:3e:6c:9c:99 brd ff:ff:ff:ff:ff:ff
inet 192.168.24.1/24 brd 192.168.24.255 scope global br-ctlplane
valid_lft forever preferred_lft forever
inet6 fe80::f816:3eff:fe6c:9c99/64 scope link
valid_lft forever preferred_lft forever
6: docker0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN
link/ether 02:42:a1:61:6e:84 brd ff:ff:ff:ff:ff:ff
inet 172.17.0.1/16 scope global docker0
valid_lft forever preferred_lft forever
7: br-int: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN qlen 1000
link/ether 56:41:ee:3e:e9:4a brd ff:ff:ff:ff:ff:ff
This is an automated cleanup. This bug report has been closed because it
is older than 18 months and there is no open code change to fix this.
After this time it is unlikely that the circumstances which lead to
the observed issue can be reproduced.
If you can reproduce the bug, please:
* reopen the bug report (set to status "New")
* AND add the detailed steps to reproduce the issue (if applicable)
* AND leave a comment "CONFIRMED FOR: <RELEASE_NAME>"
Only still supported release names are valid (FUTURE, PIKE, QUEENS, ROCKY, STEIN).
Valid example: CONFIRMED FOR: FUTURE