ISP Connection Lost

Recently I have had problems with my router. From time to time I lose the connection with my ISP provider. The WAN interface says that has an IP assigned by the DHCP server but for some reason there is no connection. I have launch a tracert to and it shows that the connection is lost when trying to reach outside my private network (the only way to fix it is to reset my ISP bridge router). So I decided to create a crontab job that checks every 15 min if I am able to reach the dns server and it reports the output to the system log. This is the output that I seen in the log:

Fri Jan  7 08:15:00 2022 cron.err crond[1712]: USER root pid 4602 cmd /root/
Fri Jan  7 08:15:00 2022 user.notice root: IPv4 is Up

I have also noticed that that the DHCP lease is 7200 seconds (1.5 hours) but the WAN interface is asking to renew it after 1 hour. Why is not waiting 1.5h before the IP expires?

Tue Jan  4 23:51:25 2022 daemon.notice netifd: wan (545): udhcpc: lease of XX.XXX.XXX.216 obtained, lease time 7200
Wed Jan  5 00:51:24 2022 daemon.notice netifd: wan (545): udhcpc: sending renew to XXX.XXX.XXX.1
Wed Jan  5 00:51:24 2022 daemon.notice netifd: wan (545): udhcpc: lease of XXX.XXX.XXX.216 obtained, lease time 7200
Wed Jan  5 01:51:24 2022 daemon.notice netifd: wan (545): udhcpc: sending renew to XXX.XXX.XX.1

So this morning when I woke up I tried to connect to the wifi hostpot of my router and it connected but I could not surf on the internet. So I decided to reset again the bridge and the router and I did inmediatelly have internet after that.

Immediatelly after that, I decided to check at what moment it lost the connectivity with the internet but to my suprise there is no report of my IPv4 connectivity between 15:21 and 7:42. Why is that?

Thu Jan  6 15:21:50 2022 daemon.notice netifd: Network device 'wlan0' link is up
Fri Jan  7 07:42:40 2022 dnsmasq-dhcp[2872]: DHCPREQUEST(br-lan) 48:d7:05:d8:ed:e3

I just notice that around the time syslog shows the last recorded event (15:21) I set a new peer to my VPN wireguard server.

This is the release that I have installed on my TP-Link router: OpenWrt 21.02.1 r16325-88151b8303

fwiw, it is perfectly normal for DHCP protocol to request lease renewal, before lease expires. It usually happens at 50% of lease time. eg. after 3600 seconds? If it can't renew due to no response from the DHCP server, it tries again at 75% and so forth.

However, I'm not sure if the system log normally reports above 'normal' activity with fully working ISP connection. Someone else may be able to clarify.

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Lease renewals on WAN and from LAN clients are reported to the log by default, aside from wireless join/ leaves messages, these usually make up the bulk of the normal 'background chatter' of the log.

E.g., after 12 days of uptime (I've extended my logging buffer, so the logs above cover the whole 12 days):

# logread | grep udhcp.*renew | wc -l

# logread | grep dnsmasq-dhcp.*DHCPACK | wc -l

(My ISP has a lease time of one hour, so half-hourly lease renewals).

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