1. Home
  2. Wireless Networking
  3. Wireless router losing Internet connection (DHCP problem)

Wireless router losing Internet connection (DHCP problem)

PROBLEM: Loss of Internet connection.

BACKGROUND:

Installed a wireless router (Hawking HWR54G) on Comcast Cable Internet service that was being used for a single PC. When the wireless router failed to get a DHCP lease, I cloned the MAC address of the single PC, which seemed to solve the DHCP problem. I did this because I had seen advice on the Internet that Comcast was registering the MAC address in a semi-permanent database.

However, when the DHCP lease ran out the wireless router was unable to renew it, resulting in loss of Internet connectivity (as seen from both wired and wireless client computers). I reconnected the original PC to the cable modem in order to renew the DHCP lease, then reconnected the wireless router, but the problem recurred when the DHCP lease again ran out.

THE FIX:

Comcast Support advised me that the MAC address *isn't* registered in a semi-permanent database -- it's only retained as part of the DHCP lease. So instead of cloning the MAC address for the old DHCP lease, I should have instead obtained a new DHCP lease for the router. Here's how to do that:

  1. Make sure the wireless router is configured correctly for DHCP on a cable modem, with the default (not cloned) MAC address (restored if necessary).

  1. (Not suggested by Comcast, but it can't hurt.) Disconnect the wireless router from the cable modem and hook the original PC back up to the cable modem. Wait until it is connected to the Internet. Then open a CMD window (Start -> Run -> CMD) and run "IPCONFIG /RELEASE" (to release any existing DHCP leases). When that completes, close the CMD window, and reconnect the wireless router to the cable modem.

  2. Unplug the power on both the cable modem and the wireless router. Wait 30 seconds or more.

  1. Plug in power to the cable modem, and wait at least 30 seconds for it to power up and go online (lights resuming their normal flashing pattern).

  2. Plug in power to the wireless router, and wait at least 30 seconds for it to power up and obtain a DHCP lease.

  1. Log in to the wireless router with an Internet browser (e.g., Internet Explorer) and verify that a DHCP lease was successfully obtained.

RESULT:

The first DHCP lease obtained by the wireless router after this procedure was for only one hour. At the end of that lease the wireless router successfully renewed it, this time for a period of four days. No further DHCP problems have occurred.

Reply to
John Navas
Loading thread data ...

SPOKE TOO SOON: That "fix" gets the Internet connection working, but

*doesn't* solve the > PROBLEM: Loss of Internet connection.
Reply to
JNspam1

DEAD END: Hawking support was a dead end -- there was nothing related to the problem in the scripted answers that had been provided to the telephone support person (who had poor English and was probably located in India).

Reply to
John Navas

John Navas hath wroth:

Sigh. Where to begin?

Instant bottom line: Possible defective DHCP client in the Hawking HWR54G.

Power cycling the hardware generates a new DHCP lease request. Leaving it disconnected for a while resets the ARP table in the CMTS. Comcast does NOT register the MAC addresses of the client and has an unusually short ARP table persistance of about 15 minutes to allow juggling hardware.

DOCSIS 1.1 CPE specs at: |

formatting link
in Sect 2.1: The cable modem MUST be capable of filtering all broadcast traffic from the local LAN, with the exception of DHCP (as identified by the destination port number in the UDP header) and ARP packets.

Translation: The cable modem should block broadcasts but pass directed DHCP requests (as found when using a DHCP relay agent). Hawking undoubtably gets it right for DHCP lease requests or it would not have an initial IP address, but probably screws it up for DHCP renewals.

The big question is whom to blame. It could be that the database on the CMTS is loading the cable modem with garbage. It could also be that the Hawking HWR54G has a problem with its DHCP client implimentation. Sniffing the traffic and waiting for the Hawking HWR54G to request a lease renewal does not sound like a productive exercise. Therefore, I suggest replacing the Hawking HWR54G with something else for a while and see if the problem magically goes away.

The 4 days is the typical Comcast DHCP lease interval.

There are also others with similar and recent DHCP lease renewal problems:

formatting link
(fixed with firmware update to Netgear router). Also, for fun, try this free DHCP query tool: |
formatting link
'm not sure if till show anything because it can't generate lease renewal requests, but it might be interesting to see what it returns anyway.

Reply to
Jeff Liebermann
[POSTED TO alt.internet.wireless - REPLY ON USENET PLEASE]

Buying a better router. :) But the Hawking can't be returned (packaging discarded), and I'm trying to do this for a friend without having to spend any more money. Oh well. I've now faxed a support request to Hawking (for whatever good that will do).

That's been my guess as well. But if that is the case, I'm surprised at not seeing more complaints on the Internet.

Don't think so. Here's why:

  • I'm pretty sure the router is using its hardware (MAC) address as the identifier when requesting a DHCP lease -- that's the easiest way to generate a unique identifier, and is why MAC address cloning can be used to take over an existing lease.
  • On basic cable modem service, Comcast will only hand out one client IP, so it won't hand out a second DHCP lease while a first lease is still active. It does this by comparing the identifier of a new DHCP request to the identifier of any existing lease.
  • Comcast will hand out a new DHCP lease if the cable modem (not the router) is unplugged for less than a minute (not 15 minutes). This is presumably because the CMTS triggers immediate expiration of any existing DHCP lease when the cable modem disappears or is re-registered.

Just means the cable modem will bridge/relay DHCP Discover requests by client(s).

That's been my guess as well.

Unlikely. That would probably cause a directly attacked PC to fail the same way, which isn't happening.

More likely. Or at least some sort of compatibility issue.

I agree.

If I don't get some help from Hawking, that's what I'll have to do.

Yep.

Yep.

formatting link
I'm not sure if till show anything because it can't generate lease

It would have to be run on a PC directly attached to the cable modem and configured with a fake static configuration (so any new DHCP lease request isn't rejected by Comcast), and I personally doubt it would show anything interesting with regard to the router lease renewal problem. Also, it fails to create a System Restore point when installing, and tries to remove a system DLL when uninstalling. Color me unimpressed.

Reply to
John Navas

SHOCK AND AWE: Hawking responded to my support email request in a matter of hours with new firmware for the router. I'll update this thread when I've had a chance to test it.

Reply to
John Navas

UPDATE: The emailed firmware is Version 1.1 Release 22, as compared to Version 1.0 Release 11 on the website, and is clearly a major revision. For example, the Web interface is totally different, and much snappier. I'm cautiously optimistic -- the router obtained a Comcast DHCP lease without difficulty, and manual Release-Renew works, but I won't know for 4 days if automatic lease renewal also works.

Reply to
John Navas

NOTE: For those following this in detail, this is the >> Rev M UPDATE: The emailed firmware is Version 1.1 Release 22, as compared to

Reply to
John Navas

I have the the exact same router (HWR54G rev.M) and am having the same problem with DHCP lease renewal. I'm curious to hear if the new firmware has fixed the problem and where/who did you get the new firmware from. I contacted hawking tech support to notify them of my problem and to ask if a newer firmware was available and was told there is no such firmware (version 1.1 release 22).

I either need to fix this router or send it back and get something else. Having a router that needs to be reset every hour is pretty annoying. I've gone back to using my old wired router until I get this worked out.

Thanks > NOTE: For those following this in detail, this is the >> Rev M of the Hawking HWR54G wireless router.

Reply to
Ralph Schaffner
[POSTED TO alt.internet.wireless - REPLY ON USENET PLEASE]

The new firmware, which I received by email >I have the the exact same router (HWR54G rev.M) and am having the same

Reply to
John Navas

Got told the same thing by tech support over the phone today... they said Version 1.0 release 11 was the newest.

I've emailed support ( snipped-for-privacy@hawkingtech.com), referencing this thread, hoping to get a better answer.

Curiously enough, this site:

formatting link
references an even higher firmware version number: Version 1.6 Release

  1. Anyone heard anything about that?
Reply to
weston

Cabling-Design.com Forums website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.