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What's the idea behind using overlapping subnets for the LAN and the mesh?

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What's the idea behind using overlapping subnets for the LAN and the mesh?

Interfaces on the mesh have an IP in the range Devices you connect to the LAN behind the node will have IP addresses in the 10.x.x.x/29 or /30 range. These ranges overlap. Mesh interfaces will see all LAN addresses as part of their local link, but LAN device interfaces will see the wider mesh as a separate subnet. If two LAN subnets have the same network prefix, each subnet will be unable to access the other because they will see the foreign addresses as part of their own subnet.
I'm sure there's a reason for this? Is it because it's too expensive to do duplicate address detection? Why not use IPv6? That would pretty much eliminate the risk of address conflicts.

K6CCC's picture
You are incorrect.  A smaller

You are incorrect.  A smaller subnet within a larger subnet works just fine and you are using it every time you get onto the internet.  A computer on the local LAN will see for example a subnet of  It will know that it can directly access -  Further, it will know that anything else in will need to use as a gateway (the LAN address of my hAP).  Further, anything on the mesh will know that - are reachable via (the mesh address of my hAP) due to the OLSR propagation.  In routing tables, smaller subnets take precedence over larger subnets.

OK, this was a very simple explanation.  Someone else may expand on it.

nc8q's picture
overlapping subnets for the LAN

+1 K6CCC


Not just an overlap, but the local 'LAN address' network  is completely inside the 'Primary address' network.
In the AREDN firmware there is logic to assigning a 'LAN address' network that attempts to avoid a conflict.
Should you find a conflict, you may manually set your 'LAN address' network.
The largest allowed network is /27 and that allows for 262,144 subnets.
The default (/29) allows 1,048,576 subnets.
So, as an AREDN network approaches one million nodes, there is an ever increasing chance of a conflict.

" 'mesh' is a topology, not a protocol."

73, Chuck


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