Unable to obtain Dynamic IP/use Internet from Cable Modem

This thread has been locked for further replies. You can start a new thread to share your ideas or ask questions.

Unable to obtain Dynamic IP/use Internet from Cable Modem

This thread has been locked for further replies. You can start a new thread to share your ideas or ask questions.
Unable to obtain Dynamic IP/use Internet from Cable Modem
Unable to obtain Dynamic IP/use Internet from Cable Modem
2021-07-29 13:26:23 - last edited 2021-07-31 00:02:20
Model: Archer AX50  
Hardware Version: V1
Firmware Version: 1.0.9

Greetings, I have hit a bit of a dead-end regarding a newly purchased AX50 router (I wanted to take advantage of WiFi 6 speeds in a new environment and use link aggregation to boost throughput to a NAS device). I have a long history with computers and know my way around networking, but I am stumped.

 

Using a laptop, I can connect directly to a cable modem (Arris SB8200) and access the internet as normal. However, upon attaching the modem to the blue WAN port (I've tried both patch and regular Ethernet cables), I am unable to obtain the dynamic IP issued by the modem. I have tried everything I could think of over the last few hours, including releasing/renewing the lease, power cycling every piece of hardware in the connection, etc. I also attempted to get the router to work by setting up the connection as a static IP. I was hoping that if I copied the known working values (IP/subnet/gateway), that this would allow me to get online initially and troubleshoot further from there, but no such luck. I have also tried connecting directly to a desktop computer with a different MAC address, as well as cloning the MAC address from the laptop I was testing, just in case my ISP was not telling me the truth regarding MAC registration.

  0      
  0      
#1
Options
1 Accepted Solution
Re:Unable to obtain Dynamic IP/use Internet from Cable Modem-Solution
2021-07-29 13:35:28 - last edited 2021-07-31 00:02:20

@tonyrayo 

 

Just for troubleshooting, can you try if it makes any difference if you set the "Internet Port Negotiation Speed" to "100Mbps Full Duplex"?

You can find that setting under "Advanced" -> "System Parameters".

 

Recommended Solution
  2  
  2  
#2
Options
6 Reply
Re:Unable to obtain Dynamic IP/use Internet from Cable Modem-Solution
2021-07-29 13:35:28 - last edited 2021-07-31 00:02:20

@tonyrayo 

 

Just for troubleshooting, can you try if it makes any difference if you set the "Internet Port Negotiation Speed" to "100Mbps Full Duplex"?

You can find that setting under "Advanced" -> "System Parameters".

 

Recommended Solution
  2  
  2  
#2
Options
Re:Unable to obtain Dynamic IP/use Internet from Cable Modem
2021-07-31 00:01:26

@woozle Never underestimate the power of fiddling and stubbornness. I mistakingly changed too many variables at once, but everything seems to be up and running correctly! It is also possible that stale/old settings from testing at a different location were to blame. Thank you for the tip, it might have done the trick!

  1  
  1  
#3
Options
Re:Unable to obtain Dynamic IP/use Internet from Cable Modem
2021-08-04 18:14:48

@tonyrayo @woozle  - This worked for me after sitting on with the ISP forever , changing the modem (Motorola), buying another router to make sure I wasn't crazy and god knows how many different fiddling I did.

 

Here's the problem ... the link speed negotiation goes to 100mb down BUT I pay for 400mb down and thus I am capped at 100mb from the router.  Tested without the router and the speed is 450mb down.  Sooooooo any thoughts on how to ge this speed past the 100/Full and back to the 1000/Full?

  0  
  0  
#4
Options
Re:Unable to obtain Dynamic IP/use Internet from Cable Modem
2021-08-04 22:48:11

@TVP74 

 

So, with negotiation speed set to "100Mbps Full Duplex" it works fine, but with the setting "1000Mbps Full Duplex" it doesn't?

 

There are only two things that I can think of.

Either the quality of the Ethernet cable is not sufficient (but I am sure you've tried more than one cable already) or there is some rare compatibility issue between the Ethernet chips of the Motorola modem and the router.

 

Do you happen to have an old Gigabit Ethernet switch lying around at home? In case you do, can you test what happens if you plug it in between the Motorola modem and the router? (so that one Ethernet cable goes from the modem to the switch and a second Ethernet cable from the switch to the Internet/WAN port of the router)

  0  
  0  
#5
Options
Re:Unable to obtain Dynamic IP/use Internet from Cable Modem
2021-08-05 10:18:27

@TVP74 

As mentioned in the previous post, the WAN cable quality plays big role.

If the cable is dark gray, with a crimped RJ-45, its probably Cat 5/e.
Those are okay, but if the distance increases over 10-20-30m, it will not be able to support 1Gbps. Plus, if its physically damaged, it could have some of the wires cut.

Check how long is the cable, and if its Cat5e, you will probably have to request from your ISP, to change it with a Cat6a.

Or even better, if they can get fiber up to your router, and then connect with media converter.

  0  
  0  
#6
Options
Re:Unable to obtain Dynamic IP/use Internet from Cable Modem
2021-08-05 20:01:42

Thank you for the replies... the cable is Cat5e used to test with (spare) and yes I do have a business class 10/100/1000 switch , brand new 16 port (my house is was pre-wired because I work in IT)

 

I have a ticket open.... just waiting to see what the results will be ... 

  0  
  0  
#7
Options

Information

Helpful: 0

Views: 1040

Replies: 6

Related Articles