B20 connectivity issue -- a tale of two MODEMs


#1

I’m working on a problem Balance 20 running FW 7.0.0. Both WANs are connected to cable MODEMS served by Spectrum (formerly Time-Warner), provisioned at 60/5. One MODEM is a Motorola 6141; the other is a Netgear CM400 (both DOCSIS 3.0, 8/4 streams.)

Here’s the problem: The B20 shows the Motorola 6141 as “connecting” but never connects. (The Netgear works fine.)

Here’s what I did to troubleshoot:

  1. Talked to Spectrum to find out what they could see. They reported both on-line with forward/reverse path levels well within spec.
  2. Changed ethernet cables (using only new cat 6 cables).
  3. Connected a computer directly to the ethernet jack on the Motorola MODEM. The Spectrum rep was correct – the MODEM was on line and operating fine.
  4. Disconnected/powered-down both MODEMs and powered them up one at a time, the Motorola first. Once the Motorola MODEM showed itself to be on-line I then powered-on the Netgear.

No matter what I do the B20 reports “IP Address: (none) Status:Connecting…” for the Motorola MODEM – even though it is “known good.” Note: The Motorola MODEM was working fine the day prior. NO changes were made to its configuration in the B20 and there were no cabling changes – still using the same WAN port.

Hugely frustrating. I’ll appreciate any thoughts/insight.

Rick


#2

What is your health check set at? After you apply a configuration and the dashboard reloads, give it a couple of seconds and you will see the CPU spike. This is when the config actually gets applied. If you have any OSPF or RIP stuff enabled (especially on a WAN interface), try disabling it. Broken routes that get advertised may cause what you are seeing.


#3

Would you please open a support ticket here for support team to check ? This will allow us to identify the issue.


#4

Hi. Thoughtful answer – TU! In this case the B20 does not even get an IP address. Just says “connecting.” One thing I did do is make the health check super generous. But, in this case – so far as I can see – no health checks are made/failed as there is no "connection " to the WAN.
No OSPF/RIP/etc enabled – not needed in this application.


#5

TU Sitloongs. Ticket 772748 created. - Rick


#6

Do both WAN connections share the same default gateway? I ask because my two wan links have the same default gateway IP, but there were two different Mac addresses for the same IP gateway. I never could get it to give me good performance until I put a balance 30 between the Balance One and the modem. Basically, the Balance One now has two distinct gateways and now I have good performance.

Have you done a packet capture to see that the dhcp request is going out?


#7

Hi. All good thoughts. TU.

The two Spectrum/T-W default gateways are different and the subnets from which the IP addresses of the modem are different (although neither should make no difference).

I did not do a packet capture once I found a computer, when connected directly to the MODEMs (one at a time, obviously) confirmed that the MODEMs were 100% operational. The MODEMS had no problem registering on the Spectrum system and seemed to be provisioned correctly.

Interesting note (which makes ZERO sense to me). I opened the referenced support ticket this morning. Shortly thereafter, I powered down the non-contingency MODEM and when I brought it back up – the B20 connected to it!

We’ll see what the Peplink engineers say about this. Given that the MODEM worked fine with a computer but not with the Peplink … well …


#8

Are there any devices between the modem and the Peplink? I am wondering if the modems will only flush ARP caches when it sees a physical disconnection (which wouldn’t occur with an intermediary switch in the path)

I had a similar issue with my balance 30 and it ended up being a faulty network interface (hardware failure). A quick RMA later - back in business.

Good luck sir!


#9

Hi. Nope. Both MODEMs are connected directly to the B20. Now a flaky ehternet port on the B20 is a possibility. That’s one of few things, it seems to me, that may explain why no connectivity to the B20 but operation with a PC was fine. That may also explain why when I went to the B20 this morning it connected to the MODEM just fine – after failing to do so 15-20 times yesterday!
Strange.
Tnx once again for your thoughts.