Router Gateway issu

recently found a problem, such as when the IP address is 192.168.96.190 and the gateway is 192.168.8.1, there is no default route. When the IP address is 192.168.96.190 and the gateway is 192.168.96.1, there is a default route.
what is this phenomenon?

Sep.19,2021
MySQL Query : SELECT * FROM `codeshelper`.`v9_news` WHERE status=99 AND catid='6' ORDER BY rand() LIMIT 5
MySQL Error : Disk full (/tmp/#sql-temptable-64f5-1b318e9-4d441.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1b318e9-4d441.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
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