ssh root@192.168.1.1 "grep -F 'ubios-udapi-server: ubios-udapi-server: wanFailover: eth8 is' /var/log/messages* | cut -d':' -f 2- | sort | tail" 2>/dev/null
example output:
Jun 14 20:08:19 UDM-Pro user.info ubios-udapi-server: ubios-udapi-server: wanFailover: eth8 is down: {"alarm":true,"dns_alarm":0,"id":"eth8","lat_avg":14933,"loss_pct":21.052600860595703,"std_dev":1399,"type":"wanFailover"}
Jun 14 20:08:19 UDM-Pro user.info ubios-udapi-server: ubios-udapi-server: wanFailover: no change (eth8: down, eth9: down+off)