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"Mesh Gateway" and lack of VLAN Tagging Support

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Fri, 12/18/2015 - 18:46
#1
W2GMD
W2GMD's picture
"Mesh Gateway" and lack of VLAN Tagging Support

I'm trying to setup a internet-connected mesh as follows:

[Laptop] <-Ethernet-> [NSLM900] <-900MHz-> [NSLM900] <-Ethernet-> [Internet GW]
​But I'm having a little trouble understanding how to configure the Internet-connected NSLM900. It's a single-port device connected to a dumb-switch, to-which the Internet GW is also connected. I'm not able to connect, nor do I see a DHCP lease on the WAN side of the NSLM900. A screen shot of my configuration follows. As far as I know the dumb-switch isn't stripping VLAN tags, so the lack of a VLAN-enabled switch shouldn't be the issue.

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Fri, 12/18/2015 - 18:57
K5DLQ
K5DLQ's picture
If you want your node to
If you want your node to access the internet, a VLAN switch is REQUIRED.
See:
http://www.aredn.org/content/device-device-linking-dtdlink
and
http://www.aredn.org/content/understanding-vlans
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Fri, 12/18/2015 - 19:10
(Reply to #2)
W2GMD
W2GMD's picture
Mea Culpa. I was Groking the
Mea Culpa. I was Groking the tagging configuration incorrectly. For future reference, the WAN sub-interface will ONLY see tagged frames. I was under the mistaken idea that it could see all frames on a dumb-switch, and thus, should work

Thanks!
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Fri, 12/18/2015 - 19:32
(Reply to #3)
K5DLQ
K5DLQ's picture
no problem.  Yes, normally a
no problem.  Yes, normally a dumb switch will drop "tagged" frames as they are larger than the expected size.  (I think switches that support jumbo frames may not, but, that's just a guess).
 
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Sun, 12/20/2015 - 00:56
(Reply to #4)
KG6JEI
Actually an 802.3 (Ethernet)
Actually an 802.3 (Ethernet) switch should pass through the packet so long as the CRC checks out and it's below the max frame size. (Ignoring any filtering and other funny stuff that exists on managed switches)

802.3ac (1998) increases max Ethernet frame size by 4 bytes to 1522. This allows for a full size frame (1500 bytes payload + ethernet encapsulation + VLAN) to transit an unmanaged "dumb" switch.  Now I'm not sure exactly how many switches adopted this standard or when they adopted it if they did but even ignoring this standard change, unless your packet contained a payload greater than 1496 bytes of data adding on the VLAN header on top would still be below the pre 1998 raised max frame size and manage to pass its way through.  At that point one would be playing roulette with "will this packet make it through" but any packet that isn't full frame size (and a fair number will not be its just the way packets are) will make it through even legacy gear. 
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