My RUT240 (running in bridge mode) was reconnecting every hour and interrupted internet access for 15-20 seconds. After a few months i fixed it by installing an external antenna (wtf?).
Yesterday i made a big mistake, i installed the latest firmware and now the interrupts are back:
Tue Jan 19 03:49:32 2021 daemon.notice netifd: ppp_4 (8626): udhcpc: sending renew to xx.xx.xx.xx
Tue Jan 19 03:49:32 2021 daemon.notice netifd: ppp_4 (8626): udhcpc: bind(UDP): Cannot assign requested address
Tue Jan 19 03:49:32 2021 daemon.notice netifd: ppp_4 (8626): udhcpc: sending renew to 0.0.0.0
Tue Jan 19 03:49:32 2021 daemon.notice netifd: ppp_4 (8626): udhcpc: lease of xx.xx.xx.xx obtained, lease time 7200
Tue Jan 19 03:49:32 2021 local1.info hotplug-gsmstate[26751]: envACT: ifupdate
Tue Jan 19 03:49:32 2021 local1.info hotplug-gsmstate[26751]: envDEV: wwan0
Tue Jan 19 03:49:39 2021 local1.notice fwblock[27192]: Started fwblock
Tue Jan 19 03:49:39 2021 local1.notice fwblock[27192]: Applying SSH blocks
Tue Jan 19 03:49:39 2021 local1.notice fwblock[27192]: Applying WebUI blocks
Tue Jan 19 03:49:40 2021 user.notice firewall: Reloading firewall due to ifupdate of ppp_4 (wwan0)
Tue Jan 19 03:49:41 2021 local1.notice fwblock[27292]: Started fwblock
Tue Jan 19 03:49:41 2021 local1.notice fwblock[27292]: Applying SSH blocks
Tue Jan 19 03:49:41 2021 local1.notice fwblock[27292]: Applying WebUI blocks
Tue Jan 19 03:49:42 2021 local1.info hotplug-gsmstate[27357]: envACT: ifupdate
Tue Jan 19 03:49:42 2021 local1.info hotplug-gsmstate[27357]: envDEV: wwan0
Tue Jan 19 03:49:44 2021 user.notice firewall: Reloading firewall due to ifupdate of ppp_4 (wwan0)
Tue Jan 19 03:49:45 2021 local1.notice fwblock[27565]: Started fwblock
Tue Jan 19 03:49:45 2021 local1.notice fwblock[27565]: Applying SSH blocks
Tue Jan 19 03:49:45 2021 local1.notice fwblock[27565]: Applying WebUI blocks
I think i found a temporary solution: login as root and type: killall netifd && chmod 0 /lib/netifd
This problem exists at least one year. Can you please finally fix it? The only "fix" you provided was to remove the "LAN cable is unplugged" log message, this isn't a real fix. In NAT Mode the problem doesn't exists.