R7000 internet connection every 30 min - What controls WAN lease time - Router, cable modem, ISP?

[N6AC]

What controls WAN lease time - Router, cable modem, ISP ?

ISP recently changed all neighborhood IPs, apparently as part of some maintenance.

Now I see -

Lease Obtained     0 days,1 Hours,0 Minutes
Lease Expires     0 days,0 Hours,57 Minutes

... And in the R7000 logs, repeats of this every hour -

[Time synchronized with NTP server] Friday, Jul 15,2016 05:36:21
[Internet connected] IP address: 72.99.99.99, Friday, Jul 15,2016 05:36:20
[Time synchronized with NTP server] Friday, Jul 15,2016 05:06:21
[Internet connected] IP address: 72.99.99.99, Friday, Jul 15,2016 05:06:20

... which may explain why Netflix kept going black periodically last night.

NO related hourly entries in the cable modem log.

router = R7000, fw=V1.0.5.70_1.1.91  

cable modem = Motorola SB6120

P.S. this did not happen before Cox changed the WAN IP ...

Help please ...

[TheEther · Accepted solution]

In the WAN, the ISP controls the lease time.  The DHCP protocol mandates that a device must request an extension of the lease no later than halfway through the lease, so 30 minutes into a 1 hour lease is expected.  Lease extension is supposed to be seamless and should not cause any loss of service.  

It's not uncommon for ISPs to use a short lease.  IIRC, I once had an ISP that used 5 minute leases!  That's kinda short but in the grand scheme of things it's not a big deal.  It's only a few packets so it won't impact the speed of your service.

[TheEther · Accepted solution]

In the WAN, the ISP controls the lease time.  The DHCP protocol mandates that a device must request an extension of the lease no later than halfway through the lease, so 30 minutes into a 1 hour lease is expected.  Lease extension is supposed to be seamless and should not cause any loss of service.  

It's not uncommon for ISPs to use a short lease.  IIRC, I once had an ISP that used 5 minute leases!  That's kinda short but in the grand scheme of things it's not a big deal.  It's only a few packets so it won't impact the speed of your service.

[N6AC]

Thank you for the information!