Continuous rebooting of BIG-IP 4200 box

Here's a tip I go often to check the logs when these conditions happen.

Goto the log folder & see what action has caused the reboot to happen. Usually the HA-STATUS condition would be defined in settings, it would look something like below.

---------------------------------------------------------------------
Sys::HA Status
Feature               Key          Action                        Fail
---------------------------------------------------------------------
config-not-recvd      sod          go-offline                    no
crypto-failsafe       cn-crypto-0  none                          no
crypto-failsafe       cn-crypto-1  none                          no
crypto-failsafe       cn-crypto-2  none                          no
crypto-failsafe       cn-crypto-3  none                          no
crypto-failsafe       cn-crypto-4  none                          no
crypto-failsafe       cn-crypto-5  none                          no
crypto-failsafe       cn-crypto-6  none                          no
crypto-failsafe       cn-crypto-7  none                          no
daemon-heartbeat      bcm56xxd     restart                       no
daemon-heartbeat      bigd         restart                       no
daemon-heartbeat      cbrd         restart                       no
daemon-heartbeat      mcpd         restart-all                   no
daemon-heartbeat      scriptd      restart                       no
daemon-heartbeat      snmpd        restart                       no
daemon-heartbeat      sod          restart-all                   no
daemon-heartbeat      tmm          go-offline-downlinks-restart  no
daemon-heartbeat      tmm1         go-offline-downlinks-restart  no
daemon-heartbeat      tmm2         go-offline-downlinks-restart  no
daemon-heartbeat      tmm3         go-offline-downlinks-restart  no
daemon-heartbeat      tmm4         go-offline-downlinks-restart  no
daemon-heartbeat      tmm5         go-offline-downlinks-restart  no
daemon-heartbeat      tmm6         go-offline-downlinks-restart  no
daemon-heartbeat      tmm7         go-offline-downlinks-restart  no
daemon-heartbeat      tmrouted     restart                       no

Nevertheless, goto your log file & search for this keyword. Because when some action is triggered by setting, the same log will be captured with "action is to reboot"/ "action is to failover and reboot"

less /var/log/ltm | grep -i "action is"

or

less /var/log/ltm | grep -i boot

with that being said, you can know what is causing the reboot & you can update your setting accordingly. My guess, your vlan failsafe is enabled. So when traffic is not coming to your box, tmms gets restarted & links go down & reboot happens.