On corner / extreme cases hardware might experience difficulties reading optics or even MIC/PIC cards.
On MX Series routers, these logs can be found over >show log messages and they should be repetitive if there's a problematic state with the hardware.
Mar 1 13:01:00 2024 MXlab05 afeb0 PQ3_IIC(WR): no target ack on byte 0 (wait spins 3)Mar 1 13:01:00 2024 MXlab05 afeb0 PQ3_IIC(WR): I/O error (i2c_stat=0xa3, i2c_ctl[1]=0xb0, bus_addr=0x41) Mar 1 13:01:00 2024 MXlab05 afeb0 MAX6956(grp=162,dev=65): Failed write of 51 Mar 1 13:01:00 2024 MXlab05 afeb0 mic_sfp_present : MIC(1/0) - Error to get the input port for link 7
In Case of other MX where there is no afeb, below logs can came:Mar 23 21:13:57 MX_TEST : %PFE-3: fpc10 PQ3_IIC(WR): no target ack on byte 0 (wait spins 2) Mar 23 21:13:57 MX_TEST : %PFE-5: fpc10 MIC(10/0)(1): SFP+ unplugged Mar 23 21:14:00 MX_TEST : %PFE-3: fpc10 PQ3_IIC(WR): no target ack on byte 0 (wait spins 2) Mar 23 21:14:00 MX_TEST : %PFE-3: fpc10 PQ3_IIC(WR): I/O error (i2c_stat=0xa3, i2c_ctl[1]=0xb0, bus_addr=0x51) Mar 23 21:14:00 MX_TEST : %PFE-5: fpc10 MIC(10/2)(1): SFP+ unplugged Mar 23 21:14:04 MX_TEST : %PFE-5: fpc10 MIC(10/2)(1): SFP+ plugged in
All described logs about chassis not able to read or write information internally (I/O messages, error to get input, no ack obtained) it will have unexpected behaviors on chassis like interfaces not going UP, quick loss on read of FRU units(fpc, pic).
If logs are spotted on MX104 routers then the Forwarding Engine might be experiencing this problematic state.
afeb0 PQ3_IIC(WR): no target ack on byte 0 logs point to transient failure happening on the AFEB (Forwarding Engine).
Be sure first that this chassis don't have installed any NON-JUNIPER SFP that are known cause of these messages (See KB31238 [juniper.net]).
Solution: Plan Maintenance Window time and restart Forwarding Engine. It can be afeb restart or a fpc line card restart depending on the source of the log (afeb0 on this example).
request chassis afeb restart
If logs are spotted for other MXs routers then corresponding FRU needs to be restart.
request chassis fpc slot <fpc-slot-number> restart If the issue is seen repeatedly even after restarting the FPC/AFEB, contact Support for further investigation and assistance.