This article provides the cause for the vsrx ukern_ipc_msg_write: IPC message type: 1032, subtype: 18 exceeds MTU, mtu 1400, length 2208 log message to be reported on vSRX devices that are running Junos OS Release 18.2R2, 18.3R1, or 18.4R1.
vsrx ukern_ipc_msg_write: IPC message type: 1032, subtype: 18 exceeds MTU, mtu 1400, length 2208
It also indicates whether any action is required to resolve the message and lists the Junos OS releases in which this problem has been fixed.
The following message appears repeatedly in the messages file of the SRX/vSRX device that is running Junos OS Release 18.2R2, 18.3R1, or 18.4R1.
May 03 07:51:01 vsrx001 usp_ipc_client_send: failed to send message via ipc pipe May 03 07:51:02 vsrx001 ukern_ipc_msg_write: IPC message type: 1032, subtype: 18 exceeds MTU, mtu 1400, length 1664 May 03 07:51:02 vsrx001 usp_ipc_client_send: failed to send message via ipc pipe May 03 07:51:03 vsrx001 ukern_ipc_msg_write: IPC message type: 1032, subtype: 18 exceeds MTU, mtu 1400, length 1528 May 03 07:51:03 vsrx001 usp_ipc_client_send: failed to send message via ipc pipe May 03 07:51:04 vsrx001 ukern_ipc_msg_write: IPC message type: 1032, subtype: 18 exceeds MTU, mtu 1400, length 1936 May 03 07:51:04 vsrx001 usp_ipc_client_send: failed to send message via ipc pipe May 03 07:51:05 vsrx001 ukern_ipc_msg_write: IPC message type: 1032, subtype: 18 exceeds MTU, mtu 1400, length 1800 May 03 07:51:05 vsrx001 usp_ipc_client_send: failed to send message via ipc pipe May 03 07:51:06 vsrx001 ukern_ipc_msg_write: IPC message type: 1032, subtype: 18 exceeds MTU, mtu 1400, length 1664
Communication between the Routing Engine and the Packet Forwarding Engine takes place via Inter-Process Communication (IPC) messages. Typically, the size of these IPC messages is somewhere around 1300 bytes with 1400 bytes being the permissible upper limit.
However, due to a software modification in Junos OS Releases 18.2R2, 18.3R1, and 18.4R1, the IPC messages were being generated with a length greater than 1400 bytes, causing the above messages to be reported in the logs.
This behavior has been fixed in Junos OS Releases 18.2R3, 18.3R2, 18.4R2, 19.1R1, and 19.2R1.
Meanwhile, these messages can be ignored because they are purely informational and are not traffic disruptive.