Update : Maestro Fails to Connect to 6XXX via Internet using SmartSDR 2.0.x.x

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This is an informational update on my inability to use my Maestro or PC running SmartSDR for connection to several Flex 6xxx radios around the country. 

I want to thank David, K8DM who has put in many hours on this helping me.  He now has his 6700 deployed in N.J. and it is working fine from his Maestro at his home in Alexandria, VA.  Although, I am still unable to connect to it or to three others that I know of, my own 6300, a unit in North Carolina and one in Colorado.

In my case it seems to point to Comcast Northwest dropping fragmented packets.  I doubt it's limited to Comcast Northwest, nor do I think all Comcast systems contribute to the problem that I'm having so be on the lookout in your system and please let us know what you experience.

The first link below is to a post I put up last week on this subject.  Between this post and the one it links to you will get an idea of what the problem is for several of us.  In the second article, be sure to scroll down to the comments made by Steve Hicks at Flex.


As you can see,Tim at Flex has acknowledged the problem is a bug in SmartSDR and has characterized it as a priority but there is no time estimate for resolution.  It's been several months since this problem first surfaced and three months since it was acknowledged by Steve Hicks.

In the mean time, K8DM and I have been trying to see where the problem is in the path between the server (Flex 6xxx) and the Client (Maestro or PC running SmartSDR). 

Inasmuch as many connections work fine even with the bug, we thought we might be able to attack the problem from the ISP end of things while Flex works to fix the bug.
At this point in our testing it seems that the road block we are seeing is in the Comcast Northwest system where my Maestro is deployed.  Keep in mind, this may not be isolated to Comcast Northwest as any system could be setup to drop fragmented packets.  Apparently they have been used in the past as exploits which may seem like a good reason for the ISP to discard them out of hand.

On the other hand, K8DM has his Maestro deployed in a different Comcast system in VA and has no difficulty connecting to his remote 6xxx in N.J..

Here's a link to Wikipedia where IP Fragmentation is described. 


From what we can tell, SmartSDR generates large packets in both the Maestro or PC.  These packets apparently carry the waterfall and spectrum scope data.   When they are larger than the path Maximum Transmission Unit (MTU) they are fragmented into payloads small enough to pass through the smallest MTU in the path between the server (Flex 6xxx) and client (Maestro or PC running SmartSDR).

K8DM has a 6700 and a Maestro which were both first deployed in a Comcast network at his home in Virginia.  The 6700 is now at a remote location in N.J.  I have a 6300 and a Maestro deployed in a Comcast network in the Seattle, WA area.  I am unable to receive waterfall or spectrum data on either my Maestro or PC running SmartSDR, version 2.0.19.  Earlier tests with another 6xxx in Colorado and another in North Carolina using 2.0.17 were also unsuccessful from this location and these two locations cannot receive waterfall and spectrum data between them.

This points to Comcast dropping the SmartSDR packets for reasons I don't understand.  In an effort to eliminate my equipment as the problem, I've switched out two modems and three routers over the last few days.

The modems are an Arris TG-862 modem/router and a Netgear CM500V which is a modem only.  The routers are an Asus RT-N10P, the router portion of the TG-862 above and a Peplink Balance 20.  I've used the 862 in routing mode and in bridge mode as appropriate.  I've also connected to a neighbors Comcast/Xfinity Hotspot and my daughters Comcast Wifi in another nearby city.  Connecting with the PC to the neighbor's Xfinity hotspot, I drew a public IP address presumably eliminating all in-home routers in the path near the PC. 

Every one of these Comcast/Xfinity paths has connected to K8DM but failed to receive waterfall and spectrum display data.

On the other hand, during testing with K8DM or with my own 6300, I've had no trouble connecting the Maestro or PC to the two radios using my AT&T hotspot, a Verizon hotspot, or the WiFi at a pizza restaurant.  K8DM has had no trouble from his Virginia home which is Comcast to his remote 6700 in N.J. which gets Internet from Optimum Cable.

I had a Comcast technician out today and it turned out that I was educating him with what little I know.  He said he would talk to his supervisor about this and maybe I'd hear something back.

It seems that my situation and anyone else who finds themself in the same predicament is going to have to wait on Flex to make our WAN remote work for us.
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Bob - W7KWS -

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Posted 2 years ago

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