Last Modified: Nov 07, 2022
See more info
Known Affected Versions:
12.1.0, 12.1.0 HF1, 12.1.0 HF2, 12.1.1, 12.1.1 HF1, 12.1.1 HF2, 12.1.2, 12.1.2 HF1, 12.1.2 HF2, 12.1.3, 184.108.40.206, 220.127.116.11, 18.104.22.168, 22.214.171.124, 126.96.36.199, 188.8.131.52, 184.108.40.206, 12.1.4, 220.127.116.11, 12.1.5, 18.104.22.168, 22.214.171.124, 126.96.36.199, 12.1.6, 13.0.0, 13.0.0 HF1, 13.0.0 HF2, 13.0.0 HF3, 13.0.1, 13.1.0, 188.8.131.52, 184.108.40.206, 220.127.116.11, 18.104.22.168, 22.214.171.124, 126.96.36.199, 188.8.131.52, 184.108.40.206, 13.1.1, 220.127.116.11, 18.104.22.168, 22.214.171.124, 126.96.36.199, 13.1.3, 188.8.131.52, 184.108.40.206, 220.127.116.11, 14.0.0, 18.104.22.168, 22.214.171.124, 126.96.36.199, 188.8.131.52, 184.108.40.206, 14.0.1, 220.127.116.11, 14.1.0, 18.104.22.168
15.0.0, 22.214.171.124, 126.96.36.199
Opened: Apr 20, 2018
The MTU of the tmm_bp kernel interface may be out-of-sync with the value of sys db vlan.backplane.mtu as well as out-of-sync with the MTU displayed by the following command: tmsh show /net vlan all-properties -hidden.
From the data plane perspective, this issue can cause excessive IP fragmentation on tmm_bp VLAN and high CPU usage. In some cases it also causes packet loss. From the config perspective, this issue has a few smaller impacts: -- Fragmented packets on the tmm_bp interface for those packets greater in length than the actual MTU of this interface as given by the kernel in response to the command: ip address list dev tmm_bp | egrep -i mtu or $ifconfig tmm_bp. Note: This has no impact to the running system. Fragmented packets are reassembled in order for TCP clients of the tmm_bp interface. -- The sys db variable vlan.backplane.mtu may be out-of-sync with the value of the MTU of the kernel interface tmm_bp as given by either of the following commands: ip address list dev tmm_bp ifconfig tmm_bp -- Similarly, the sys db variable vlan.backplane.mtu may be out-of-sync with the value of the MTU of the Net::Vlan tmm_bp as returned by the command: tmsh show net vlan -hidden tmm_bp Paraphrasing: The value of VLAN tmm_bp MTU (as found in vlan.backplane.MTU) is not applied to the corresponding kernel interface.
This issue occurs on first-boot after upgrading to versions later than v12.1.1 HF1.
A series of subsequent restarts rolls the correct setting by issuing the following commands, in sequence: tmsh stop sys service all tmsh start sys service all To verify the setting is correct, issue the command: ip addr show dev tmm_bp ; tmsh show net vlan -hidden tmm_bp \; list sys db vlan.backplane.mtu