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mikecr
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09/23/2026 7:57 PM

IP address renews every hour on the hour

There's something amiss with DNS IP address renewals for the past three months with my connection.  What happens is that my firewall submits a DNS request, the Comcast DNS server does not renew my IP for a few seconds, and then gives me back the same IP address!   Today alone it's reliably happened every hour on the hour, which is the DNS refresh interval.  This means that there are regular, constant internet outages, and it interrupts streaming constantly.   How do we get this fixed?

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11 hours ago

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EG

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3 days ago

DNS servers do not renew IP addresses. DHCP servers do. Also, DNS servers are demand-based. They do not continuously ping or query domain names in the background like on a timer. That said, this sounds like the DHCP server settings are somehow set for issuing short-term leases. Can you clarify if you mean WAN/public IP addresses from the Comcast system, or LAN/private IP's from a home router's DHCP server ?

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mikecr

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@EG​ You're correct of course, it's DHCP and I'm talking about the Comcast-issued public IP address.   (I get DNS errors during these outages which is why I made that mistake when I posted).

I was told by an I-T person that there is a handshake between Comcast and my firewall, and that something is amiss causing Comcast to deny continued access to the exiting IP, then doling out a new one which usually is the same one I'd had before.  Hope that makes more sense.   And thanks!

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2 days ago

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EG

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2 days ago

No worries ! 😊Ok so this typically happens when they are doing routine maintenance or upgrades to their network. 1 hour leases get issued and many times result in a new / different IP being assigned. This should go back to longer-length leases (3-4 days) being issued when the work is completed.

What puzzles me is that renewals should be completely seamless and not result in any drops....

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mikecr

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@EG​ We agree on this.  However this behavior has been going on and off since July!  It went away for awhile, and I got an IP that was quite different from these "every hour renewal" ones.   That lasted perhaps two weeks, and now it's back to this hourly stuff.   Do we agree I should not be getting this type of behavior for weeks and weeks?  If so, what can be done?   Thanks again.

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1 day ago

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XfinityCliff

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Hello @mikecr, and thanks for sharing your experience and findings here on our Xfinity Community forums!  (And thanks @EG for offering valuable feedback and spotlighting this for us! ❤️)

I can definitely understand the concern, especially since you’ve been seeing this on and off for several months. The DNS errors seem like a symptom of the connection briefly dropping. Normally, a DHCP renewal should happen without interrupting your connection, even if you receive the same public IP address again.

Since you’re using a firewall, I’d take a look at the WAN/DHCP logs around the exact time this happens.  If your modem provides event logs, it would be helpful to see if any connection or synchronization errors line up with the same times.

Please note: if you post any log details here, you should scrub them for personalized data first. (Things like mac addresses and public IP's should be partially obfuscated - i.e. present the mac like **:**:**:**:AF:D3, and IP like *.0.241.12) 

It would also be helpful to know the make/model/firmware of the firewall appliance you're using and your top network configuration - Modem model, is it operating in bridge mode (assuming it is but never hurts to check), speed tier you're operating at on the service, etc. 

If possible, testing with another router/firewall could also help narrow down whether this is happening at the firewall or further upstream. The biggest clue will be what your firewall reports during that hourly renewal, since a normal DHCP renewal (regardless of  how long the lease may be) shouldn’t regularly interrupt your Internet connection.

Any additional details you can provide would help us to narrow this down. 

I am an Official Xfinity Employee.
Official Employees are from multiple teams within Xfinity: CARE, Product, Leadership.
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15 hours ago

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mikecr

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@XfinityCliff​   Thanks!  Understood, and I'll begin compiling this information to post once I have it all.   FYI the modem is indeed in Bridge Mode.

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14 hours ago

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mikecr

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@XfinityCliff​ 

Here is an example from the firewall logs.  Basically this happens over, and over, and over, well, you get the idea!   The firewall is a Sophos XGS-128.  Firmware is SFOS 22.0.2 MR-2-Build546.

The modem has a part # on the  My plan is the 1G plan.   The code says "XFSETUP-4F34"

udhcpc: lease of 24.63.*.* obtained, lease time 7200
udhcpc: sending renew to 69.241.109.140
udhcpc: lease of 24.63.*.* obtained, lease time 3599
udhcpc: sending renew to 69.241.109.140
udhcpc: lease of 24.63.*.* obtained, lease time 7200
udhcpc: sending renew to 69.241.109.140
udhcpc: lease of 24.63.*.* obtained, lease time 3601
udhcpc: sending renew to 69.241.109.140
udhcpc: lease of 24.63.*.* obtained, lease time 7200
udhcpc: sending renew to 69.241.109.140
udhcpc: lease of 24.63.*.* obtained, lease time 3599
udhcpc: sending renew to 69.241.109.140
udhcpc: lease of 24.63.*.* obtained, lease time 7200
udhcpc: sending renew to 69.241.109.140
udhcpc: lease of 24.63.*.* obtained, lease time 3600
udhcpc: sending renew to 69.241.109.140
udhcpc: lease of 24.63.*.* obtained, lease time 7200
udhcpc: sending renew to 69.241.109.140
udhcpc: lease of 24.63.*.* obtained, lease time 3599
udhcpc: sending renew to 69.241.109.140
udhcpc: received DHCP NAK
udhcpc: sending select for 24.63.*.*
udhcpc: lease of 24.63.*.* obtained, lease time 7200
INFO    ; Sep 20 09:52:11Z  ; SYSTEM ; ND_MAIN        ; command string: dhcp {"if_config":[{"interface":"Port2", "ip":[{"ipfamily":"0","ipaddress":"24.63.*.*","netmask":"255.255.252.0","action":"dhcpdown"}]}]};
WARNING ; Sep 20 09:52:11Z  ; SYSTEM ; JSON_PARSOR    ; Unable to find handler for key: if_config;
INFO    ; Sep 20 09:52:11Z  ; SYSTEM ; LINK           ; ;
INFO    ; Sep 20 09:52:11Z  ; SYSTEM ; IP             ; Total Interface = 1;
INFO    ; Sep 20 09:52:11Z  ; SYSTEM ; IP             ; interface = Port2;
INFO    ; Sep 20 09:52:11Z  ; SYSTEM ; IP             ;    Total IP addresses = 1;
INFO    ; Sep 20 09:52:11Z  ; SYSTEM ; IP             ;        address[0] = 24.63.*.*;
INFO    ; Sep 20 09:52:11Z  ; SYSTEM ; IP             ;        peeraddr[0] = (null);
INFO    ; Sep 20 09:52:11Z  ; SYSTEM ; IP             ;        netmask[0] = 22;
INFO    ; Sep 20 09:52:11Z  ; SYSTEM ; IP             ;        family[0] = 0;
INFO    ; Sep 20 09:52:11Z  ; SYSTEM ; IP             ;        ip_assignment[0] = 0;
INFO    ; Sep 20 09:52:11Z  ; SYSTEM ; IP             ;        scope[0] = 0;
INFO    ; Sep 20 09:52:11Z  ; SYSTEM ; IP             ;        sequence[0] = -1;
INFO    ; Sep 20 09:52:11Z  ; SYSTEM ; IP             ;        mtu[0] = 0;
INFO    ; Sep 20 09:52:11Z  ; SYSTEM ; IP             ;        ismbim[0] = 0;
INFO    ; Sep 20 09:52:11Z  ; SYSTEM ; NEIGH          ; Total Interface = 0;
WARNING ; Sep 20 09:52:11Z  ; SYSTEM ; LINK           ; Not Found any data for LINK.;
INFO    ; Sep 20 09:52:11Z  ; SYSTEM ; IP             ; IP Command; ip -4 address delete 24.63.*.*/22 broadcast + dev Port2 scope global
INFO    ; Sep 20 09:52:11Z  ; SYSTEM ; IP             ; Reply = '0';
INFO    ; Sep 20 09:52:11Z  ; SYSTEM ; ND_MAIN        ; time taken for do_nd_action is 0.000000.;
INFO    ; Sep 20 09:52:11Z  ; SYSTEM ; ND_MAIN        ; sending reply: 0;
INFO    ; Sep 20 09:52:34Z  ; SYSTEM ; ND_MAIN        ; command string: DHCP { "if_config": [ { "interface": "Port2", "ip": [ { "ipfamily": "0", "ipassigntype": 2, "ipaddress": "24.63.*.*", "netmask": "255.255.252.0", "ipsequence": -1, "mtu": 1500, "action": "dhcpup" } ] } ] };
WARNING ; Sep 20 09:52:34Z  ; SYSTEM ; JSON_PARSOR    ; Unable to find handler for key: if_config;
INFO    ; Sep 20 09:52:34Z  ; SYSTEM ; LINK           ; ;
INFO    ; Sep 20 09:52:34Z  ; SYSTEM ; IP             ; Total Interface = 1;
INFO    ; Sep 20 09:52:34Z  ; SYSTEM ; IP             ; interface = Port2;
INFO    ; Sep 20 09:52:34Z  ; SYSTEM ; IP             ;    Total IP addresses = 1;
INFO    ; Sep 20 09:52:34Z  ; SYSTEM ; IP             ;        address[0] = 24.63.*.*;
INFO    ; Sep 20 09:52:34Z  ; SYSTEM ; IP             ;        peeraddr[0] = (null);
INFO    ; Sep 20 09:52:34Z  ; SYSTEM ; IP             ;        netmask[0] = 22;
INFO    ; Sep 20 09:52:34Z  ; SYSTEM ; IP             ;        family[0] = 0;
INFO    ; Sep 20 09:52:34Z  ; SYSTEM ; IP             ;        ip_assignment[0] = 2;
INFO    ; Sep 20 09:52:34Z  ; SYSTEM ; IP             ;        scope[0] = 0;
INFO    ; Sep 20 09:52:34Z  ; SYSTEM ; IP             ;        sequence[0] = -1;
INFO    ; Sep 20 09:52:34Z  ; SYSTEM ; IP             ;        mtu[0] = 1500;
INFO    ; Sep 20 09:52:34Z  ; SYSTEM ; IP             ;        ismbim[0] = 0;
INFO    ; Sep 20 09:52:34Z  ; SYSTEM ; IP             ;        dhcpmode[0] = ;
INFO    ; Sep 20 09:52:34Z  ; SYSTEM ; IP             ;        isdhcponly[0] = No;
INFO    ; Sep 20 09:52:34Z  ; SYSTEM ; IP             ;        rapidcommit[0] = No;
INFO    ; Sep 20 09:52:34Z  ; SYSTEM ; IP             ;        release[0] = No;
INFO    ; Sep 20 09:52:34Z  ; SYSTEM ; IP             ;        renew[0] = No;
INFO    ; Sep 20 09:52:34Z  ; SYSTEM ; IP             ;        managedflag[0] = No;
INFO    ; Sep 20 09:52:34Z  ; SYSTEM ; IP             ;        otherflag[0] = No;
INFO    ; Sep 20 09:52:34Z  ; SYSTEM ; IP             ;        prefixdelegation[0] = No;
INFO    ; Sep 20 09:52:34Z  ; SYSTEM ; IP             ;        preferredprefix[0] = (null);
INFO    ; Sep 20 09:52:34Z  ; SYSTEM ; IP             ;        preferredprefixnetmask[0] = 0;
INFO    ; Sep 20 09:52:34Z  ; SYSTEM ; NEIGH          ; Total Interface = 0;
WARNING ; Sep 20 09:52:34Z  ; SYSTEM ; LINK           ; Not Found any data for LINK.;
INFO    ; Sep 20 09:52:34Z  ; SYSTEM ; IP             ; IP Command; ip -4 address flush dev Port2
INFO    ; Sep 20 09:52:34Z  ; SYSTEM ; IP             ; IP Command; ip -4 address add 24.63.*.*/22 broadcast + dev Port2 scope global
INFO    ; Sep 20 09:52:34Z  ; SYSTEM ; IP             ; Reply = '0';
INFO    ; Sep 20 09:52:34Z  ; SYSTEM ; ND_MAIN        ; time taken for do_nd_action is 0.000000.;
INFO    ; Sep 20 09:52:34Z  ; SYSTEM ; ND_MAIN        ; sending reply: 0;

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12 hours ago

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mikecr

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Note in the logs that the DHCP NAK (negative acknowledgement) is where the trouble starts each time it tries to renew.

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12 hours ago

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EG

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16 hours ago

@mikecr Weeks seems like a long time. I can't help directly as I am not a CC employee. I can however, escalate your issue to the Comcast corporate employees (The Digital Care Team) who are available to these boards. You should get a reply here in your topic. Good luck !

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