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?

 

[Solaris17]

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?

No the modem has its own lease time. Generally this is 24 hours. Be fore flashing you can release the IP and most of the time it will fix it. In this case you can try rebooting the modem. Or just call them and have them reset the link on your modem.

Though this is usually based off of MAC address and you shouldn’t really be experiencing this (your situation generally happens when physically changing routers)

 

[Bill_Bright]

What is it you are trying to do? Does your network work properly?

It is not uncommon to require a full network reset (or at least local network) after flashing the router's firmware. That is, unplug power from router and connected computers. Don't just power down PCs as that just puts them in standby mode and the NIC is still alive.

I would also unplug power for the modem for a full network reset.

Wait 30 to 60 seconds then power up the modem. Wait for lights to settle down, then power up the router and wait for those lights to settle down. Then power up the main computer. I suspect you will be good to go.

Since most ISP techs have a troubleshooting checklist they cannot deviate from, and since resetting the network is always at the top of that list (because it often does fix networking issues), this is something you most likely will have to do anyway when you call them. So I recommend you reset your network. It likely will fix any IP assignment issues. But if you still have problems, you can then tell tech support you already did it - though they will likely have you do it again because it is on their checklist and the don't have the authority to deviate from it.

 

[videobruce]

Everything is ok now, I did power cycle the Modem, but I wanted to avoid doing that.

Let me ask this, what exactly does the "DHCP Release & Renew" function in the Router do?

 

[FordGT90Concept]

DHCP Release & Renew basically tells the router above yours (at the gateway address) "give me new IP." If that router is not running a DHCP server, it has no effect (because static addresses).

 

[OneMoar]

the modem handles the WAN DHCP from the MDD/CMTS it just forwards that to the router
all release/new does is reset the routers lease for that ip

if you want to change the ip on spectrum you need to change the routers MAC, hit apply and then reboot the modem

 

[videobruce]

DHCP Release & Renew basically tells the router above yours (at the gateway address) "give me new IP." If that router is not running a DHCP server, it has no effect (because static addresses).

When you say "that router" not running DHCP, are you meaning my Router or theirs at the HE?

the modem handles the WAN DHCP from the MDD/CMTS it just forwards that to the router
all release/new does is reset the routers lease for that ip
if you want to change the ip on spectrum you need to change the routers MAC, hit apply and then reboot the modem

The initial problem was, that address was not passed along to the Router, not until I rebooted the Modem. I don't/didn't want to change the address, I wanted the Router to get it again preferably w/o rebooting the Modem.

If I did nothing, would the Router eventually get recognized again? And how long?
Also, in that state, I could not access the Modem.

 

[FordGT90Concept]

Theirs. Routers assign IPs to their subordinates either statically (manual assignment) or dynamically (DHCP server). Their router/DHCP server is assigning your router the WAN address you see. Your router's DHCP server is assigning addresses to your computer and devices.

If I did nothing, would the Router eventually get recognized again? And how long?
Also, in that state, I could not access the Modem.

What model is this modem? If there is a modem, it looks like your router is using PPPoE or similar to control the modem. In which case, you should be able to look at the router logs to see what error the modem is giving. Most likely it will say something down the lines of being unable to obtain an IP from the provider. In other words, there's too much noise in the line to get connected. A lot of ISP provided modems will only try once before they give up. This is why you have to power cycle the modem (forces it to try again). High end/non ISP modems will try again every few seconds until it gets connected so power cycling them usually doesn't accomplish anything.

If there is a physical modem and you couldn't access it via your intranet, either the modem is dead/dying or the cable connecting the router to the modem is garbage.

 

[Bill_Bright]

I did power cycle the Modem, but I wanted to avoid doing that.

Why? It does no harm and in fact, often restores performance as it forces the ISP servers to refresh all the settings on their side too - a good thing.

DHCP Release & Renew basically tells the router above yours (at the gateway address) "give me new IP."

True - well, kinda sorta. "Renew" does not automatically imply a "new" (IE, "different") IP address. The fact is, it is almost certain the same addresses from the ISP will be reassigned back to the same MAC address. ISPs typically use a semi-static type assignment system. Their network will "dynamically" assign a "new" IP when you first subscribe to their service, but then that IP becomes tied to the MAC address of the gateway device (typically the modem). So even if you disconnect for a week or even longer, when you connect again, it is not uncommon for the same IP address to be assigned to your modem again.

In fact, I recently purchased a new modem which of course, required me to contact my ISP to get it authenticated on their network. It was assigned the same IP address as my old modem - they just linked it to the new MAC address of the new modem.

About the only way I can get a different IP assignment from my ISP is if hackers and bad guys have spoofed my IP and suddenly my IP gets blacklisted because of the bad guys activities. But this is a pain because I would almost have to prove my innocence (that I was not the bad guy). Proving innocence if often much harder than proving guilt.

Of course that was my ISP (Cox). Others may do it differently.

 

[OneMoar]

if the router doesn't have a LAN ip in the 192.168.0.0 range you won't be-able to access the modems webui (ddwrt's default DHCP lease on the WAN port is a little long if it doesn't expire directly after the modem goes down it won't switch to a LAN subnet right away, also if the modem encounters a issue and looses lock on the tFTP server some weirdness can occur, remember cable modems get there config and firmware from the isp MDD at boot the factory image is keep for when it can't establish a connection to the DOCSIS provider)

if you changed from stock to ddwrt firmware then yes a physical reboot is required,also a good idea after a router firmware upgrade if the dnsmasq daemon is updated

dd wrt takes a good two min to fully come back online after a reboot, the web ui doesn't always refresh the wan ip right away

I don't quite understand what you think your 'problem' is because there isn't one everything behaved exactly as intended,eventually it would have gotten anouther DHCP advertisement and been fine (up to 180 seconds AFTER ddwrt fully boots)

@FordGT90Concept PPoE is not a thing on cable . thats DSL,

 

[videobruce]

Theirs. Routers assign IPs to their subordinates either statically (manual assignment) or dynamically (DHCP server). Their router/DHCP server is assigning your router the WAN address you see. Your router's DHCP server is assigning addresses to your computer and devices.

If there was a Router connected, then disconnected (for a few minutes), with the Modem still connected, when the same Router gets reconnected, shouldn't the 'handshake' (if that is the correct term) be re-established with no other user intervention?

The Modem logs are normal. There are some reoccurring, supposed 'error' messages, but they show on a regular basis when there are no issues. The logs in the Router don't show anything either.

True - well, kinda sorta. "Renew" does not automatically imply a "new" (IE, "different") IP address. The fact is, it is almost certain the same addresses from the ISP will be reassigned back to the same MAC address. ISPs typically use a semi-static type assignment system. Their network will "dynamically" assign a "new" IP when you first subscribe to their service, but then that IP becomes tied to the MAC address of the gateway device (typically the modem). So even if you disconnect for a week or even longer, when you connect again, it is not uncommon for the same IP address to be assigned to your modem again.

The reason for hitting the Release/Renew was to get the 'handshake' back that was lost when the Router was disconnected, the reconnected. It idin't do what I thought it would. I wasn't looking for a new address, just the recognition that the Router was there.

The only way that happened is to reboot the Modem which I was hoping I wouldn't have to. Maybe I should ask this; doesn't that first server know when the Router is reconnected w/o rebooting the Modem?? It's almost as it doesn't/can't see the Router when it back on.

dd wrt takes a good two min to fully come back online after a reboot, the web ui doesn't always refresh the wan ip right away
I don't quite understand what you think your 'problem' is because there isn't one everything behaved exactly as intended,eventually it would have gotten anouther DHCP advertisement and been fine (up to 180 seconds AFTER ddwrt fully boots)

I purposely waited over 5 minutes and the Router never go it's WAN address back.

 

[Bill_Bright]

The only way that happened is to reboot the Modem which I was hoping I wouldn't have to. Maybe I should ask this; doesn't that first server know when the Router is reconnected w/o rebooting the Modem?? It's almost as it doesn't/can't see the Router when it back on.

Not certain what you mean by "first server". If you mean the ISP then no, they cannot see what's on the other side (your side) of their modem. That's the beauty of using a router (even if you only have one computer connected). The modem only sees one connected device. It does not know if it is a router or a computer. You can have 30 computers connected on your side of your router and the ISP only sees one connected device, the router. They can surmise by the amount of traffic more than one computer is connected but they sure cannot see individual devices. Neither can the bad guys! At least not unless you, as the user and always weakest link in security, let them in.

 

[FordGT90Concept]

If there was a Router connected, then disconnected (for a few minutes), with the Modem still connected, when the same Router gets reconnected, shouldn't the 'handshake' (if that is the correct term) be re-established with no other user intervention?

The Modem logs are normal. There are some reoccurring, supposed 'error' messages, but they show on a regular basis when there are no issues. The logs in the Router don't show anything either.

This indicates that the problem is further up the chain so you can't do anything to fix it. I would try to tracert google.com when it happens and it should clearly show which hop has problems. Forward the results of the tracert to your ISP.

 

[videobruce]

I did and I have. Lool at the 2nd hop, that was what I was referring to, thats an aggreated router isn't it righ after the CMTS??

 

[flmatter]

https://arstechnica.com/civis/viewtopic.php?f=10&t=1415155
So how does this compare to what you are being told here?
Did you buy a new router or still trying to figure things out from your last thread about troubleshooting the router? https://arstechnica.com/civis/viewtopic.php?f=10&t=1415747

 

[FordGT90Concept]

I did and I have. Lool at the 2nd hop, that was what I was referring to, thats an aggreated router isn't it righ after the CMTS??

That looks perfectly normal to me:
Hop 1 = your computer to your router (LAN)
Hop 2 = your router to your ISP (WAN)
Hop 3-6 = Road Runner trunk lines

>100ms is slow.
>1000ms is bad.
Unreachable is broken.

 

[videobruce]

https://arstechnica.com/civis/viewtopic.php?f=10&t=1415155
So how does this compare to what you are being told here?
Did you buy a new router or still trying to figure things out from your last thread about troubleshooting the router? https://arstechnica.com/civis/viewtopic.php?f=10&t=1415747

Additional input, except for that last grossly incorrect claim about causing the problem which I responded to accordingly.
I'm looking for another Router, troubleshooting is over, I have wasted way too much time on this already.

That looks perfectly normal to me:
Hop 1 = your computer to your router (LAN)
Hop 2 = your router to your ISP (WAN)
Hop 3-6 = Road Runner trunk lines
>100ms is slow.
>1000ms is bad.
Unreachable is broken.

I misspoke, I meant the 3rd hop with the 1/2 second peak latency & the 80ms jitter (labeled "var") that my VoIP provider believes is causing my dropped phone calls.

 

[flmatter]

OK I know this question is related to your other thread, somewhat relevant here. So when you plug your main machine directly to the modem, you have no issues? How long do you leave it plugged directly in, hour or 2 or a day? Once you connect your router in and start setting up devices on it, that is when crashes start happen( lag spike, latency drop connection)?Is it immediately after you connect everything back up or does it take time, a couple of hours... day or 2? Last question have you felt/touched the router when these issues start? I know it sounds redundant, but just clear the air. I know its frustrating but trying to help as is everyone else.
Like I stated in your other thread if and when you go to buy a router, go AC1200 or higher. Bestbuy has them starting around $80.
Mods can move this is deemed OT. apologies in advance

 

[videobruce]

I only have connected the PC directly for less than 10 min. Doing so, I loose my VoIP service.
The issue can be triggered by maxing out or close to the connection speed of 100Mpbs. Again, this is ONLY with dd-wrt F/W (three versions around the past 2 months). openwrt is fine that I have been running for over a week now. I did a silimar test with TP's stock F/W. Same thing. The only thing I haven't done is to go back a 2-3 years which I was told it wasn't recommend over at the ddwrt forum. Ironically, that original version I installed 3 or so years ago didn't have the problem, but my Internet service was only 30Mbps, not 100.

I have the Router (as I do with the Modem & ATA) mounted on a board on the wall with additional 'standoffs below and above the units to help air flow. The PCB is large, larger than many, components are spread out, assuming purposely to aid air flow. I'm always concerned about excessive heat.
The only one that get 'fairly warm' is the Modem. The Router barely gets warm and the processor % I never have seen above 80% and the 'load' level, the only time I have seen it above 1.00 is running the Bandwidth Monitor and that isn't continuous. These figures were during testing with openwrt, but I was able to do limited testing with dd-wrt, but due to the issue, it was just that, limited.

Everything has been connected to the Router, the other devices are either off, or in a 'hot standby' mode (if you will). Active, but not really doing anything other than some low level communicating with the associated service servers. (VoIP & TiVo). It's just myself & my wife using her phone playing Scrabble (believe it or not).

I even went back to Spectrums site to go they their "certified" list of Modems. They have 4 levels, the 400Mpbs is their highest "certified" with entries and this Zoom Modem is there which kinda surprised me.

 

[FordGT90Concept]

I misspoke, I meant the 3rd hop with the 1/2 second peak latency & the 80ms jitter (labeled "var") that my VoIP provider believes is causing my dropped phone calls.

That's likely a router miles away from you (if not hundreds). You can't fix that. All you can do is complain up the chain and hopefully whomever owns it will fix it.

 

[Bill_Bright]

I agree, if it is the 3rd hop, there is nothing you can do on your end. If it is consistent, you might call your ISP and see if they can route a different way.

 

[FordGT90Concept]

I suspect that's not the cause of all your problems though. Some hops will be slower than others.

DD-WRT might have QoS problems which is why it breaks VOIP.

 

[videobruce]

That 'hop' is 1 mile away, I can walk there easily. I have contacted them more than once, the 3rd time I went to the States PSC and put in a complaint. They have changed the route more than once, with a different IP address for the 2nd & 3rd hops (same building AFAIK) , but the variance & jitter is still there. No, I don't believe that is the cause of this issue, but I believe it is for VoIP, but at least a contributing problem.
That location has been the HE for the City since the 70'3. That 3th hop is the HE (or was) the HE for some of the suburbs. Two different systems which is another reason their system here is a mess. They ran out of band aids.

 

[Bill_Bright]

A 1/2 second is a long time and not normal. That's why I said, "if it is consistent". But if this is in one of your ISP's facilities, you are at their mercy.

What does Speedtest.net show for your bandwidth? Check your contract to make sure you are getting what you pay for. If not, contact your ISP and complain. Hopefully, the contract states a minimum and not something vague like “up to” some speed.

If Speedtest shows you are getting at least the required minimums, then you are not going to convince them they need to make any changes on their end.

 

[videobruce]

Bandwidth tests show fine, that has not been an issue. But, lack of bandwidth isn't a VoIP issue, unless it's not there at all.