Router & Modem WAN IP address questions

[videobruce]

Trying to understand the events involved for a Router to get recognized with a WAN IP address thru a Modem. This is with a CATV ISP (Spectrum/TWC if that matters)

Flashing the firmware, or any activity that requires disconnection of the link between the Modem & the Router.
Modem & Router on line,
WAN cable disconnected from Modem to flash Router,
After flash, WAN cable reconnected, connectyion to Modem shows active via LED indicators on both devices,
PC can access Routers web interface ok, and clinest get populated ok also (they have static IP address set within the devices),
Router does not have a WAN address, any Gateway or any DNS address from the ISP yet.

The "DHCP Release & Renew" function in the Router isn't that suppose to solve this without rebooting the Modem?

 

[XavierMace]

It's supposed to, yes. Some modems do an extremely crappy job of handing out DHCP leases.

 

[videobruce]

Why wouldn't the existing "lease" still be in effect? It was less than 10 minutes that the cable was disconnected, same Router, same MAC address.
That DHCP Release/Renew, is for the Router or is it for the Clients??

I didn't mention, I couldn't access the Modem either until it was power cycled.

 

[mv2devnull]

That DHCP Release/Renew, is for the Router or is it for the Clients??

Consumer GUI's tend to have separate sections for "WAN" and "LAN" options. Where is your "Release/Renew" button?

The WAN-port of your router is a DHCP-client that contacts a DHCP-server. That DHCP server is either in the modem, if that modem acts as a router too, or on ISP's server behind the modem-cable-modem link. If the modem does not route, then it does not need any IP (except for management needs, which there should be next to nothing).

Yes, the DHCP client should request address on startup and the server should serve. The modem, unless the server itself, ought be totally transparent.

Take any device and hotplug a wire. The NIC does react to the appearance of the link, propagates event to OS, and interface is activated with negotiation of MDIx, speed, duplex, etc. All that is not instant (although it is closer instant on some devices).

 

[Malogeek]

Make sure the modem is in bridge mode if it has that option anywhere.

 

[videobruce]

Consumer GUI's tend to have separate sections for "WAN" and "LAN" options. Where is your "Release/Renew" button?

The WAN section.

The WAN-port of your router is a DHCP-client that contacts a DHCP-server. That DHCP server is either in the modem, if that modem acts as a router too, or on ISP's server behind the modem-cable-modem link.

I have run into this before, actually too many times this confusing misuse of the term "Modem" to mean what it says it is AND to mean a combo Modem/Router. Don't take this personally, but that is wrong, leading to more confusion! Things are confusing enough with Networking starting with way to many abbreviations & acronyms that one needs a photographic memory to remember. 😡

Haven said that, I have just a "Modem". But thanks for the description of the exact differences between the two. I initially thought a Modem needed a IP address being in the "chain".

 

[videobruce]

To put this in a separate post, the reasons for the initial questions are;
Various problems with Internet access either dropping completely or it slowing down to a crawl (almost literally).

One issue that I wasn't aware of was ingress due to a less than ideal shielded run of RG6 that was replaced. Another is a what I feel is a jitter and huge variation in latency issues with their (Spectrum/TWC) 1st aggregated router that I have provided numerous TraceRoute graphs/charts (from different programs) to them that apparently causing intermittent VoIP issues. They don't seem to think these are issues, but my VoIP provider says differently.

The above isn't the concern now. What is is the need to reboot the Modem (power cycle) to get the CMTS to reissue the lease (or whatever is the correct terminology) to my Router since anytime I update/change the F/W for the Router or disconnect the WAN cable to the Router, the WAN credentials are empty and don't get renewed. (I never just let it go and waited to see if they would on their own more than a couple of minutes since I have no intention to wait for who knows how long).

Is the problem the CMTS, the Modem (doubtful according to what has been posted), the Router, the Routers firmware, or a combination of the above.