General Discussion
Related: Editorials & Other Articles, Issue Forums, Alliance Forums, Region ForumsWhen someone says that the modem was setting the DHCP, instead
of the router, what, exactly, does that mean?
SoCalDem
(103,856 posts)Baitball Blogger
(46,573 posts)DisgustipatedinCA
(12,530 posts)...that you were being assigned an IP address for your computer, but instead of the router providing that address, your DSL or cable "modem" is providing that address. Not sure what problem you're having, but if the wrong device is trying to give your computer an IP address, it's likely going to give you one that won't work with your setup. Therefore, it's best to have only one device providing DHCP.
Baitball Blogger
(46,573 posts)It just doesn't make sense that they would provide an IP Address without "the bridge" because my Iphone didn't recognize my IpAddress until they fixed it.
DisgustipatedinCA
(12,530 posts)Many cable modems and the like can either be set up as a "router" or a "bridge". When they're set in router mode, they have a front door and a back door, if you'll allow. The front door (WAN) is in one IP network, and talks to the first device it reaches that belongs to your Internet service provider. That piece of equipment is also in the same network that your outside interface (WAN) is in. The router has another interface, AKA "back door", in my poor analogy. It's also called the LAN interface, or sometimes the inside interface. It is on a completely different IP network than your WAN interface. It shares network address space with all your devices--pc's, printers, DVR, whatever is network-connected. That's where the name comes in: the router routes data packets from one network to another.
A bridge, on the other hand, has inside and outside interfaces that are in the same IP network. It has an IP address, but don't think of it as an address on its "inside" or "outside" interfaces, since those concepts don't apply in a bridge. In the case of a bridge, the IP address is in place so that technicians can reach it remotely to fix it or monitor it.
So my guess is that the ISP tech couldn't find your WAN address to save his life, and therefore could not get into the device to make whatever changes he needed to make. So he sent a command that reprovisioned your modem as a bridge, and used some automated tool that spits out the IP address of newly-provisioned equipment, and at that point, he was able to get in.
I realize none of this matters, that your issue is fixed, etc. Just thought I'd throw it out there for general interest.
Baitball Blogger
(46,573 posts)Can the bridge access settings in my router? Can it figure out which ports I'm using for port forwarding?
DisgustipatedinCA
(12,530 posts)The device is set to either one mode or the other.
The port forwarding is interesting additional information. Port forwarding requires a router, not a bridge. So maybe the tech changed the mode to a bridge so he could get into the device, and then set it up as a router again. Or maybe I'm all wet with my previous guess. But port forwarding requires something called network address translation, or NAT. NAT, in turn, requires a router (a "layer 3 boundary" . Port forwarding is normally set up so that you can get to various devices behind your router from the outside. Since you only have a single IP address out on the open Internet, your iPad and DVR and laptop are all seen as the same IP address out on the Internet (browse to www.whatismyip.com from 2 different pc's in your house, and you'll see both share the same address out on the Internet). But if you're out there somewhere--at a hotel or coffee shop or work--and you need to get to 2 different devices at home, that's hard to do when both of those devices are using the same IP Address on the open Internet. That's where port forwarding comes in. The solution is to create a table running in the memory of your router that contains translations at the IP and port level--kind of the same as saying 'make sure to put the street address AND the ZIP code on the envelope. So if your public IP address is 50.50.50.25, for example, someone on the outside might put into a web browser 50.50.50.25 : 9500, or 50.50.50.25 : 9501. The browser is going to the same IP address in either case, but on the first connection, it's going to Port 9500, while on the second connection, it's going to Port 9501. The table in the router knows that when it receives something on port 9500, it should send the data to PC1, and when it receives something on port 9501, it's going to PC2.
So, yes, that's a longwinded way of saying that however the ISP technician got into your router/bridge, and whatever original problem he had accessing it, once inside he would be able to see your port forwarding settings. A final example, assuming the outside (shared) address of 50.50.50.25, PC1 has the address 192.168.1.100 and PC2 has the address 192.168.1.101, and both are "listening" on port 80 (i.e., they're both web servers), then the port forwarding table would look something like this:
50.50.50.25 : 9500 <---> 192.168.1.100 : 80
50.50.50.25 : 9501 <---> 192.168.1.101 : 80
In your particular case, I think you said you were dealing with a DVR. I don't know the ins and outs of network-connected DVR, or how this is set up by cable providers, but maybe the port forwarding is so that your ISP can get to both your DVR and to your router? Sometimes, port forwarding is used not for two machines on the inside as I described, but for the router itself, and for some device behind the router. So the actual IP address is configured on the router itself, but a certain port or ports is configured, using port forwarding, so that they can get to your DVR.
(edited to remove accidental and spontaneous emoticons)
Baitball Blogger
(46,573 posts)Creepy to think they can figure out the port. But they still have to know the passwords to get to the devices.
Response to DisgustipatedinCA (Reply #2)
markpkessinger This message was self-deleted by its author.
Drew Richards
(1,558 posts)If its working ok with no problem then the wan interface on the router is in bridged mode and passing what ever dhcp addresses and little subnet that the modem is pushing forward..not the best way to do things...but it can work.
Preferably you want the wan to dynamically pick up the address from the modem or even better a static assignment...and you let your router do dhcp for your internal network.
Otherwise it is causing you to loose network connectivity and ticking you off...make your router do your dhcp for internal and you will be fine.
Baitball Blogger
(46,573 posts)I just can't imagine why they didn't bridge it from the start.
idwiyo
(5,113 posts)It looks like your computer is trying to establish a network connection through modem. In theory.
Really would need a bit more info about your actual setup, which cables connected where, etc.
Baitball Blogger
(46,573 posts)It's all working good now--until the IPAddress changes, I suppose.