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Author Topic: Weird routing / DHCP problem  (Read 4615 times)

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Offline Mishakim

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Weird routing / DHCP problem
« on: April 25, 2015, 03:26:06 pm »
My network started having all sorts of problems lately, and I ultimately got it fixed, but it raised a question about the Almond+'s routing function. On my network, my cable modem / gateway is set to bridged mode, and the Almond+ handles dhcp and routing. I also had a pair of TiVos on the coax using MoCa, one of them also connected to the almond by Ethernet and acting as a bridge for the other. I had reconfigured the almond to assign IP addresses in the 192 range, but my devices were all taking addresses in the 10.0.0.x range, and thus not talking to the things with fixed addresses. I connected to 10.0.0.1 and found my neighbor's Comcast modem, which said all my devices were connected to it through MoCa. I turned off MoCa on the bridging TiVo, and everything retuned to normal, after some reboots.

So the question (aside from why Comcast isn't properly isolating customers and why TiVo doesn't let you secure the MoCa network) is, why did the Almond let the neighbor's router take over? Is it normal that a rouge router on a LAN port takes precedence over the built-in router? Can I block that?  I now know the MoCa is a security risk unless I put my own filter on it, so I won't go back to that setup, but would like to know for the future

Offline Zimmie

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Re: Weird routing / DHCP problem
« Reply #1 on: April 29, 2015, 07:12:32 pm »
I suspect the issue is that cable, as used in MoCA is a shared bus. Your MoCA bridge was connecting your ethernet network to your neighbor's MoCA bridge. Either his DHCP server responded more quickly and your clients ignored the second DHCP reply, or his DHCP server responded more slowly and your clients take the last DHCP reply they get. I don't actually know how clients should behave; ARP works the latter way, but I think DHCP should work like the former.

Assuming I'm right, the fix, as you discovered, is to disable the MoCA bridging. There isn't really anything Securifi could do about this. You would see the same issue if you powered up another home router and connected a cable between their LAN ports. Disabling the bridging unplugs the cable to the other router.

 

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