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Home » Kerio User Forums » Kerio Control » Cable Modem - Connectivity Problem (Cable Modem - Connectivity Problem)
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TheFirewallGuy

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I recently made the switch to the latest Control 8.2.2 Patch 1 (software appliance) coming from 7.4.2 (running on Windows). So I purchased a new computer and installed the software appliance version. Ever since I switched to the new version, I have a very difficult time obtaining an IP address from the cable modem. It appears that the cable modem first dishes out a local IP address (10.x.x.x) and then a few seconds later, it dishes out the real external IP address from the ISP. I always see the local IP address in Kerio and then usually it then switches to "Connectivity Problem". After 10 to 20 cable modem reboots and/or Kerio reboots (30-60 minutes of reboots), Kerio will eventually pick up the external IP address. If I connect the cable modem to any Windows machine or any crappy consumer-grade router, it too first sees the local IP and then it immediately switches to the external IP correctly every time without issue. I never had problems with the Windows version of Kerio. Has any one else seen this? Is this a bug in the software appliance version of Kerio? Any help would be appreciated as I am afraid to upgrade Kerio ever again because it is too difficult and time consuming to make it obtain an IP address.
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My IT Indy

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I've installed Control on multiple devices connecting to cable modems with DHCP and have seen nothing like this. Can you swap network cards?

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My IT Indy
Kerio Certified Reseller and Hosted Provider
http://www.myitindy.com
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silars

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Are you able to capture the DHCP responses?

This doesn't necessarily sound like a bug. However, this does appear to be an unusual situation. Getting multiple DHCP responses can be confusing. A client will only accept one of them. Some clients will only accept the first response, some will accept the last one. There is no specification on which one to accept.

One thing you could try is to issue a DHCP release and/or renew from Kerio, instead of rebooting.

Also, if the cable modem is issuing DHCP responses, you could look into disabling that. You really shouldn't have multiple DHCP servers, especially one serving private address space (10.x.x.x) and one serving routable address (real external IPs).
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TheFirewallGuy

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I don't have a way to capture the DHCP responses going to the Kerio PC. I can connect the cable modem to a Windows PC and Wireshark the DHCP communication.

How does one properly release/renew within the Kerio software appliance? There doesn't seem to be an obvious way to do this. I have disabled the Internet interface and re-enabled it with no effect.

The cable modem is a Motorola SB 6121 and appears to be completely locked down by the ISP. It has a "config" page but everything is disabled from user editing.
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silars

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Disabling/enabling the interface may not be enough. You could also SSH to the appliance and manage the interfaces from the CLI. The reason is most modern OSes will attempt to re-acquire the same IP they had previously been given. You would need to release the IP to try to acquire a new one. A renew doesn't do much either. It is really the release process.

Depending on your provider, you should be able to use any DOCSIS compliant cable modem, even your own.

I'm guessing on where that extra DHCP response is coming from. It may not be the cable modem. The only way to tell would be to get a capture of the DHCP frames/packets. A capture from a PC and Wireshark should show the same information. You just need some insight to what is going on.

[Updated on: Thu, 20 February 2014 19:23]

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