Modem admin address while in bridge mode

After unplugging your cable modem and router for a few minutes, booting up the modem first, then plugging back in your router you still cannot login? As well as shutting down and rebooting all the devices you are using to connect? Also try connecting the modem directly to a pc or laptop.

I have an XB7 in bridge mode and can access the modem admin page no problem. And I'm on a WiFI network. You could always do a factory reset on the modem. Hopefully someone here on forums with more knowledge will have a solution.

I didn't have to power-cycle the modem after turning on bridge mode, the Linux router detected the momentary interface down and immediately did a DHCP_DISCOVER and got a new (routable) IP address.

Are you saying that a power-cycle is required in order to be able to access the admin site?

As to factory reset, I had to do that yesterday after my Internet access dropped for some unknown reason.  The symptom then was no response from the modem to DHCP request packets, which forced the adapter on the Linux router to discard its address.  At that point, after some troubleshooting, I did a factory reset, got back in to the admin page and re-enabled Bridge mode.  I had to do that twice because the first time, after setting up bridge mode AND power-cycling, the router again lost contact with the DHCP server.

I guess right now my experience says that if I power-cycle the modem I'll lose the connection again.

I'll go ahead and try it, and post the results.

I'm not saying that a power cycle is required, however when something is not working properly, then yes. I always find when something goes wonky, I unplug my cable modem and router, and shut down all my connected devices.

Plug cable modem in first and wait for it to be back fully online.

Plug in the router and wait for it to be fully online.

Then turn back on devices.

OK, now this is getting weird.  I think I may have discovered a bug.

• As you suggested, I power-cycled the modem.
• Prior to power-cycling, the Linux router/firewall's WAN interface had a valid, routable, external address (73.96.x.x).
• After power-cycling, the modem ignored all DHCP traffic, replicating the failure mode I had yesterday.

However, after the Network Manager failed to establish the connection, I ran dhclient in foreground mode to see the debug log.  Here's what I got

$ sudo dhclient -4 -d enp3s0
Internet Systems Consortium DHCP Client 4.3.6
Copyright 2004-2017 Internet Systems Consortium.
All rights reserved.
For info, please visit https://www.isc.org/software/dhcp/

Listening on LPF/enp3s0/00:01:2e:70:3b:ff
Sending on   LPF/enp3s0/00:01:2e:70:3b:ff
Sending on   Socket/fallback
DHCPREQUEST on enp3s0 to 255.255.255.255 port 67 (xid=0x4d920d0c)
DHCPREQUEST on enp3s0 to 255.255.255.255 port 67 (xid=0x4d920d0c)
DHCPDISCOVER on enp3s0 to 255.255.255.255 port 67 interval 3 (xid=0x788b750b)
DHCPDISCOVER on enp3s0 to 255.255.255.255 port 67 interval 7 (xid=0x788b750b)
DHCPDISCOVER on enp3s0 to 255.255.255.255 port 67 interval 8 (xid=0x788b750b)
DHCPDISCOVER on enp3s0 to 255.255.255.255 port 67 interval 15 (xid=0x788b750b)
DHCPDISCOVER on enp3s0 to 255.255.255.255 port 67 interval 20 (xid=0x788b750b)
DHCPDISCOVER on enp3s0 to 255.255.255.255 port 67 interval 8 (xid=0x788b750b)
No DHCPOFFERS received.
Trying recorded lease 10.0.0.101
PING 10.0.0.1 (10.0.0.1) from 10.0.0.101 enp3s0: 56(84) bytes of data.

--- 10.0.0.1 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 4.491/4.491/4.491/0.000 ms
bound: renewal in 68372 seconds.

dhclient "remembered" its previous lease from when the modem was NOT in bridge mode, pinged it, got a response, and bound the old lease to the interface.

I now have full connectivity again, but the modem is in a weird state.

• The modem's admin status page says it's in bridge mode
  
  
• The modem is actually behaving as if it's NOT in bridge mode.  With a bound address of 10.0.0.101 the modem is forwarding and NATting traffic to the Internet.
• My external IP address is back to the one I had while not in bridge mode (24.22.x.x)
• The modem is not responding to DHCP requests at all

So it appears that in order to get into bridge mode I have to

1. Factory reset the modem
2. Establish a DHCP-mediated connection to the modem (i.e. the Linux box gets a 10.0.0.x address)
3. Login to the admin page
4. Enable bridge mode; the Linux box automatically gets a new routable IP address
5. DO NOT power-cycle the modem

The modem is an Arris TG3482G (provided by Comcast, black mini-tower with only 1 status light), which I believe is obsolete and being replaced with a newer model.

Is it possible/likely that it is no longer fully compatible with Comcast's network?  Time to replace?

@jhg6308 

http://192.168.100.1 is the IP addy that is used to access the U.I. pages in the Comcast rented gateway devices when they are placed into bridge mode. The page will only have a limited function because it is now a plain vanilla cable modem. Some WAN and RF signal status items will be passively viewable.

So you're telling me a DIFFERENT address, 192.168.100.1 is used now? This is definitely a change from before, as I've always been able to use 10.0.0.1 in bridge mode.

Unfortunately, this is contradicted by my current status.  From the state described in my previous email I did the following

• Disabled "bridge mode" in the admin UI - "bridge mode" is in quotes because the modem was in a weird state
• Verified connectivity
• Re-enabled bridge mode (for real) - IP changed back to 73.96.x.x netblock
• Verified connectivity

I then noticed the router admin page refreshed itself, at 10.0.0.1

So I'm now back to where I was last month:

• Bridge mode is enabled and working correctly - DHCP requests are being passed on to Comcast's DHCP server
• The admin page is reachable at 10.0.0.1
• Attempting to connect to 192.168.100.1 times out

Clearly there are software issues in the modem. 

I will be trading in my modem for a newer model.  Is there a way to accomplish this without having to call in, navigate VR trees, and wait forever on hold?

@EG, I'm considering that option.  Since I have phone as well I'd have to price in the cost of a voice-capable EMTA, or a non-EMTA modem plus VOIP (i.e. OOMA).  There's some savings but not enough to justify the added complexity.

Which specific device is Comcast shipping to replace the Arris TG3482?

I went ahead and ordered the XB7 upgrade.  I'll post an update on its bridge-mode behavior after I get it installed.

Good luck.........

The replacement XB7 modem shipped immediately and arrived the next day.

It did not work on plugging in.  It came up (admin pages OK) but was not able to acquire an IP address (blinking white)

It was stuck in DNS-capture mode (where all DNS queries, regardless of site name, return "A 10.0.0.1"

Spent 3 hours troubleshooting with various Comcast people.  Finally someone looked up the replacement order and noted it hadn't been closed, so even though the modem showed as registered to my account, it hadn't been provisioned in DHCP. As soon as she closed the order it started working. Sigh...

So far it seems to be working fine in bridge mode, and I can get to the admin pages at 10.0.0.1.