Random loss of registration, PMP450

Hi All,

I apologize if this is the wrong forum, or if this information is already posted here. I’ve looked briefly, but not extensively to see if my issue was covered. I’m an end customer (actually my mother is, but troubleshooting her connection issues falls to me).

I have a PMP450, provided by my ISP. Their network is a 900Mhz network, a rural WISP. Periodically, the connection goes down. When it goes down, I can login to the modem PMP450 and see that the status has changed from “Registered” to “Scanning” or “Syncing”. I only have the access to the guest splash screen, as I don’t have the ISP’s credentials to login and get more information.

I’ve taken screenshots of the PMP450 splashscreen when this happens, and pushed my ISP to try to identify the issues. I strongly believe it’s a loss of connection to their tower, but they continue to say nothing is wrong, or that it could be a problem with my router, or cabling, blah blah blah. I have the following specific questions:

  1. Can the PMP450 be put into a mode where it sends logging details back to a host? If so, would it log when it loses connectivity?

  2. Does the PMP450 do NAT? My ISP claims it’s not doing NAT…but I can’t seem to see past the PMP450 when trying to SSH or Telnet into my router (in order to remotely administer the router). If so, what options do I have to turn it off, as a guest user?

Thanks in advance for any help, my ISP is quite useless at helping me, claiming “everything is fine on their end!”. They are quite adept at taking the $$$ though!

So the sad part of it is… that any help we give you won’t probably do you any good without the participation of your ISP… who you’ve already mentioned is not helpful.

From your description of the issue, my best guess is you getting periodic interference or signal drop, maybe due to it being nNLOS, that’s causing your connection to drop. 900MHz is typically used for nNLOS connections, but many other devices and operators use it for this reason, and it’s pretty typical for the band to have interference issues, which can cause these drops.

  1. Yes, there are multiple logs on the PMP450 SM, and you can even setup a syslog server to capture all the logs… but again, this requires your ISP to do something.

  2. PMP450 SM’s can be set to bridge mode or NAT mode. If you’re getting a private IP address from the radio, then you are in NAT mode. That being said, even in bridge mode, your ISP could still have things firewalled off upstream, or configured various filters on the radio to keep you from SSH’ing into your router behind the radio.

I’d ask to see if there’s a larger antenna that you could get to help give you some fade margin. I’d suggest that you ask for a static public IP address if you need to SSH into your devices.

I figured that this is the case. I’m for sure in NAT mode then, as the ip address the router receives is…a private ip address. The ISP did suggest that they can setup a DMZ on the PMP450, I might have to entertain this in order that I can get access to the router.

Since I can’t really get access to the logging capabilities of the PMP450, is there any way, as a guest, that I can get the current status? I’m thinking some kind of script that I can run periodically on my router to access the PMP450, get some status, and log it to a file. I tried to telnet to the PMP450, but I was instantly asked for credentials, which stymied me a little bit.

Thanks in advance, Ivan

I find it amusing that they tell you that they’re not using NAT, but then say that they can setup a DMZ forwarder for you.

Unfortunately with guest access all you can see is the General Status page, but that’s enough to tell you if the connection is down or not. As you noticed, when your connection is down you’ll see the stats section change from “Registered” (connected), to “Scanning” (looking for the AP) or “Syncing” (trying to connect to the AP). I guess if one were clever and knew some scripting or programming you could setup something to check and log the state of those stat items when your connection goes down.

These are all stats that your ISP should be able to much more easily gather from the AP side of things. The AP records all the registrations, and session drops, and how long your session has been active. Here’s what it looks like:

I actually took an example from a 900MHz AP and you can see some of the clients have many dropped sessions. Some of this is caused by RF issues, poor signal, or the client power cycling/turning off their radio.

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This is exactly what I was thinking, if nothing else, I could grab the text off the page, and parse out the information I need. It’s sad that it has to come to this, but I’m trying to get as much data as possible in order to fix the issue. My mother lives in a valley, and although we’ve erected a 68’ tower to get the best possible signal, it’s very possible that some tall trees along the signal path are obstructing the signal.

I see in the screenshot you’ve posted that for LUID 005, you have a very high session count. That seems like a poor quality connection? that’s probably what the connection I’m working on is like.

If I were to parse out the data from the guest access screen, what would be most useful to see the signal at the time it drops/reconnects? Signal Strength Ratio? S/N Ratio? Receive Power? Air Delay?

And yes, I’d concur that telling me that they can put my router behind a DMZ, yet they don’t have NAT turned on, makes me wonder. I don’t pretend to know all the possible modes of network devices, but if you need a DMZ, that suggests that you are somehow blocking stuff otherwise. :slight_smile:

I’d log “Receive Power”, “Signal to Noise Ratio”, and “Session Status”:

As far as those clients with high session counts are concerned, they’re all aware of their situation and if we could put them on a different/better connection we would.

If you ISP has not changed the default communities, you may be able to use SNMP to gather the statistics which you want. Hopefully, for good network hygiene, your ISP is changing the default communities or at least limiting the source IPs which can query SNMP on the radio. But if they’re not, you can get a lot of information via SNMP.

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Oh, I’m intrigued now…how can I get more information on this? is this documented in the manual?