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DtD Linking

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N7JWW
N7JWW's picture
DtD Linking

Our radio club is putting together a network. There is no central organizing per se; each member participating is putting their own equipment up and seeing who else they can reach.

I just got two CPE210s: one is north-facing, the other south-facing. I would like to physically connect them together(via a swith) for Device to Device (DtD) Linking. I would like to also plug a laptop into the switch so I can monitor things. The problem is the CPEs LAN network addresses are on different subnets. My understanding is those IP addresses get chosen based on a hash of the MAC address.

How do I configure my two CPEs to have LAN IP addresses on the same subnet?

K6CCC
K6CCC's picture
DtD configuration

How do I configure my two CPEs to have LAN IP addresses on the same subnet?



You don't, and you don't want them to be.  The two nodes do NOT use the local LAN for communicating with each other at all.  That is what the DtD connection is for.
As I understand it, the CPE210 has a single LAN port.  That port will have DtD linking on VLAN 2, WAN connection (what you would use for an internet tunnel) on VLAN 1, and the local LAN untagged.  If you plug the ports from  the two nodes into most DUMB switches, the VLAN 2 will simply pass through it so the DtD will work fine.  The untagged local LAN from both nodes will be available on the switch.  If both CPE210 nodes are set to have their DHCP server enabled, if you plug your laptop into the switch with it set to get an IP from a DHCP server, it will get an address from one of the nodes - somewhat at random which one.  However if you only enable DHCP server on one of the nodes, you will always get an address from the same node.  If you set your laptop for a static IPL address, you could set it to whichever nodes address range that you want.
Now, if you use a Managed switch that knows what VLAN tagging is, you could set up the switch so that if you plug your laptop one port of the switch, you end up on the LAN for one node, and if you plug into a different port of the switch, you would be connected to the other node.  If you need more explanation on that, just ask.

 

N7JWW
N7JWW's picture
dtd vs. tun

Thanks so much for that explanation. I'm hoping to get some clarification with some odd behavior I see. My two radios are plugged into a standalone D-Link unmanaged switch. I plug my laptop into the switch to monitor mesh activity. Nothing else is plugged into the switch. When I check mesh status, sometimes the connection between my radios shows up as tun and other times as dtd. It is a dtd connection for sure, there is no internet tunneling involved! Any idea why the radios would be confused into thinking they were connected via tunnel?

nc8q
nc8q's picture
I just got two CPE210s: one is north-facing, the other south-fac

I just got two CPE210s: one is north-facing, the other south-facing.

There is one Wi-Fi channel clear of part 15 activity in the 2.4 GHz ham band.
If you put both CPE210s on the same channel, they will likely interfere with the other's reception.
If you use channel '-1', one half of your emissions will be in the standard bandwidth of channel '1' part 15 operation.
It would be best if co-located nodes were on non over lapping channels.
Our group has 5 co-located 5.8 GHz nodes on non-overlapping channels that operate without apparent interference.
 I hope this helps,
Chuck
 

N7JWW
N7JWW's picture
Pretty much always tun now

When I first connected my devices via the unmanaged switch, it seems like the status display alternated between dtd and tun. Since my last post I've been paying close attention and it reports tun all the time. Everything seems to work, I'm just concerned something is misconfigured it the radios think there is a tunnel and not a dtd connection.

WX7L
WX7L's picture
Two TP-Link CPE210 Nodes Zip-tied Together on a Roof

I am new to AREDN mesh networking and belong to the same group as N7JWW, which currently has some 16 members spread over a roughly 2 mile by 2 mile hilly area.  Things were quite simple when we only had one person to link up with, but now with members adding second nodes and wireless routers on the same 2.4GHz channel I am seeing changes in node behavior when members put up a second node.  We even have one member who has zip tied two TP-Link CPE210 units back to back on his roof.  This member does not want to believe me when I tell him this is causing poor performance of the two units.  I suggested that if he must use this configuration that he can easily and inexpensively provide some RF shielding by putting each unit in an old bread pan.  He and some other members don't see the need for this RF shielding.  Would you please identify some material on the excellent AREDNmesh.org website or that might educate us about this issue.
73
Alan

P.S.  I've used the tern "unplanned phased array"  to draw attention to this problem, but I guess a more proper nomenclature would be  "node collocation RF interference".

nc8q
nc8q's picture
this is causing poor performance of the two units.

I have five(5) 5 GHz nodes on the same mast and they 'get along just fine'.
As long as none of the nodes have overlapping channels, all is well.
If the co-located nodes are on the same channel or over-lapping channels, there is interference.
Please tell me that the two zip-tied 2 GHz nodes are on non-overlapping channels.
e.g. channel '-2' at 10 MHz BW and channel 6 at 20 MHz bandwidth.
I hope this helps,
Chuck

 

WX7L
WX7L's picture
Two TP-Link CPE210 Nodes Zip-tied Together on the SAME Channel

Thanks Chuck for your response,
I am sorry to report the zip-tied TP-Links are on the same channel with a PVC pipe in between them.  I need something to try and educate several members about how this is not something you should be doing.  I was hoping for a hyperlink to some article or document on the AREDNmesh.org website that would explain this one facet at what to do and not to do at your QTH.
73
Alan

nc8q
nc8q's picture
try and educate several members

Hi, Alan:

 If your experience is like my experience, you will always find several folks
whose beliefs will not be modified by the mere introduction of facts or logic or common sense or
shown what works or shown what does not.

Anytime one of those two nodes are transmitting, its zip-tied companion will be deaf to all other nodes.

I have been active with our local AREDN network for 4 years.
In that time there was 1 failure to launch due to being 20 miles away and having tower elevation restrictions (near an airport).
All other failures fell into: user chose to not install the device higher than the peak of the roof of his home.

Some recommendations:
Do not try to change others.
Do not obtain more 2.4 GHz devices.
Expand your network by using devices with more than 1 Amateur Radio 'clear channel'.
Use trunking (point-to-point) between cells.

I hope this helps,
Chuck
 

WX7L
WX7L's picture
Thank You!

Chuck,

Thanks for the good advice, it has helped me.  If I can not change someone, I need to find how to get my packets around them.  However, I will share your recommendations with our group and hopefully, they will listen and learn. 

Thanks again!
Alan

AB7PA
AREDN online docs have a
WX7L
WX7L's picture
Thank You!

Thank you.  I read this three months ago and had forgotten about it.  I will include this with Chuck's recommendations.

Alan

AB7PA
Not sure if this might help

Not sure if this might help but it explains some of the basic issues with channel sharing.
link: https://www.youtube.com/watch?v=uIeMM9gMRwk

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