to be fair i did get upwards of 1gig when i had the service. this was with both a cm1000 and a sb8200 (because they said my cm1000 was the problem). unfortunately, the modem stops providing a valid IP every week or two and after months of that bs and calls/hours wasted with comcast i rolled back to 400mbps service and the problem went away. i work from home most of the week and can't have 6 hour outages every week or two.
is your host (laptop, workstation, whatever) connected straight into your modem or to a firewall then into your hosts?
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If you do upgrade please post back results after a few weeks. I upgraded from 400Mbps to 1Gbps some months back. Once on gig service every week or two my firewall (connected to my modem) would lose it's IP address. It would revert back to the temporary modem privately supplied address of 192.168.100.x. I've had Comcast at this address since 2005 and this was never a problem until I moved to gig offering. I've had both business internet and residential service from Comcast at this address.
I've chatted with some coworkers of mine that have Comcast as well as read random posts that appear to show the same behavior when on Comcast's gig service. I tried two different modems (CM1000 & SB8200), various firewalls behind the modem, and tested removing firewall and connecting modem straight to a laptop. When connected to a laptop the boot procedure is the same. Laptop intially receives a 192.168.100.x IP from my modem. Sometimes after a minute or minutes the IP would update to a "real" 24.x.x.x or 73.x.x.x IP. Other times my laptop wouldn't pull a new IP even after a long wait, but forcing a DHCP renew would pull a usable IP.
Comcast tech came onsite and tested cable plant. He replaced some things stating it wasn't as clean as it should be. Again, never had this issue since 2005 here. None of his work resulted in any change in behavior. In fact it was in this broken state when the field tech left.
I decided to switch back to 400Mbps service on 7/24/19. Since then not a single hiccup. I will let it run this way for another month or so to validate. But this indicates to me there is something different when moving to gig service that causes obtaining an IP to be a problem. It would be awesome if someone at Comcast that knows the inner workings/difference when moving to gig service could explain the issue or better yet fix it. Neither the field tech nor the Comcast first level Support folks have the visibility or ability to help resolve this problem.
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bump to gig service was done online. it was at 400 Mbps level prior. i've tried both a netgear cm1000 and sb8200.
service tech came out last week and replaced some cabling saying noise was high on line. he checked out all other cabling from street to my wall plate. when ge left my house internet was not working, but he said he did all he could.
i've verified my eth cabling is good. i have cable testers.
modem connects to a meraki mx100. problem follows when connected to other meraki firewalls and a cisco 891 router. heck the issue even happens when modem connects straight to my macbook. upon boot up modem hands laptop (or the firewall) the 192 IP. on the laptop it will sometimes pull a public IP in a few minutes. other times i have to force a dhcp renew.
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around the time i upgraded my service to 1gig a few months back i cannot go more than a few days without my modem dropping my public IP. i've tried 2 different modems and numerous firewalls (which is what my modem connects to).
i see the modem loses its public IP and hands me a 192.168.100.11 address. same happens if i connect a laptop to the modem directly. in the case of the laptop i can keep clicking dhcp renew and it will eventually pull a proper IP. in the case of a firewall connected to the modem i can't do much other than power cycle over and over and pray.
when i call comcast they blame the modem. well i've tried 2 different modems that are both on their approved list. so then they blame my firewall. i've tried multiple firewalls and all have the same problem. for years my comcast internet as worked at this address without a problem and nothing has changed in my network. so, clearly the issue is on the comcast end yet they refuse to acknowledge it or put forth any effort to resolve it.
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