RBR 750 dropping internet after lease expires, every 2-ish hours

I would ask your ISP why they are changing the WAN IP so much. Two hours seems to often for WAN IP address change. My ISP goes for days or months unless I reboot my modem. 

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osmall wrote:

After the firmware update, it seems like it survived one lease transition.  Here's the log.

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Great work, thanks.  This give the impression that the Orbi is following RFC2131 (DHCP) to the letter:

 DHCP clients are allocated leases that last for some period of time. Clients begin to attempt to renew their leases once half the lease interval has expired.[11]: Section 4.4.5 Paragraph 3  They do this by sending a unicast DHCPREQUEST message to the DHCP server that granted the original lease. If that server is down or unreachable, it will fail to respond to the DHCPREQUEST. However, in that case the client repeats the DHCPREQUEST from time to time,[11]: Section 4.4.5 Paragraph 8 [b] so if the DHCP server comes back up or becomes reachable again, the DHCP client will succeed in contacting it and renew the lease.

If the DHCP server is unreachable for an extended period of time,[11]: Section 4.4.5 Paragraph 5  the DHCP client will attempt to rebind, by broadcasting its DHCPREQUEST rather than unicasting it. Because it is broadcast, the DHCPREQUEST message will reach all available DHCP servers. If some other DHCP server is able to renew the lease, it will do so at this time. 

This is from the Wikipedia section under Reliability.

If you do happen to call Xfinity support (for entertainment, perhaps), in addition to asking how long the 2-hour IP lease is going to continue (and why), it would be fun to offer to send this Wireshark log to their "Tier 2" support to illustrate how Xfininity is not following internet standards.

DHCP requests are UDP packets, which means there is no guaranteed delivery (as with a TCP session that has been opened). It is entirely possible for a DHCP request to "go missing", or for a DHCP server to get overloaded and fail to respond.  That is why the standard is to make multiple attempts.  If the log had covered the full two hours, I would expect to see a request at 12 hours, 18 hours, 21 hours, etc. down to the point where they were just seconds apart as in the capture.

I'm also having the same issue.   Any updates?

For me, it was fixed by updating to a slightly newer firmware.  However, even though it's currently working, I am still only getting 1-2 hour DHCP leases.  The DHCP server does not respond unless the router broadcasts the request.  It doesn't respond to direct requests apparently?  Maybe Xfinity is misconfiguring it's packets and it's telling me to contact the wrong DHCP server or it's on another subnet? 

Contacted Xfinity. Got redirected to Netgear...didnt get much help. But I changed my router settings from Dynamic to Static.. seems to have worked. No more lease time.