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Used the extra pairs in cat5 cable for a DtD link

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wa2ise's picture
Used the extra pairs in cat5 cable for a DtD link
This is a fairly trivial hardware hack.  I needed to run a DtD link between two AREDN nodes (which are located far apart in the hosue), but snaking the extra cat5 cable thru my house isn't a trivial matter.  But the existing cat5 cables have two extra twisted pairs (assuming not used for POE) that I grabbed to run the DtD link.  I also did this to pipe two main router ports over one cable, to the point where they split to different rooms in the house.  This gave me the extra pairs to do the DtD link. 
wa2ise's picture
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Call me old fashion, but i
Call me old fashion, but i would of just stuck the GS105e in a spot in the room that easy easy to get to, put the injectors there, run one cable to each device and one cable back to the main router.

Much easier to field repair, less cable splicing, and less room for violating cat5e spec (don't even get me started on cat6 specs) 

But yes some vendors make adapters to do this, I've even seen the pairs split at the patch panel in some cases too (for those who are like me and have patch panels)
wa2ise's picture
Of course, but in my case the

Of course, but in my case the "easy here" spot is in an attic crawl space without power. 

And if you're handy with a soldering iron, you can make a reasonable splice of the twisted pairs using heat shrink and maintain the twisted-ness of the twisted pair.  Some experience with RF (HF and VHF) helps.  Cat5 seems fairly forgiving of impedance bumps and such (think it has some echo cancellation ability).  Though if you're running a very long (100 meter) length of cat5, you'd be more likely to not get away with it. 

zl4dk's picture
I had a similar issue when running a DtD link between a Linksys router and an Airgrid (and managed switch). I only had one cable running the length of the house and needed to run the DtD link and internet traffic over it. I didn't think to split the cable cores out but instead managed to program the Linksys and the Managed switch to run the cable between them with 2 vlans to keep the traffic separate. I know others have had trouble running Vlans on a linksys but I don't seem to have any issue with my WRT54gl. I am only running tagged traffic on this port, I believe some devices have trouble coping with both tagged and untagged traffic on the same port. I am likely to shift my airgrid at some stage and remove the need for vlans on this cable in future.
I don't understand the

I don't understand the problem. I have two units and I simply connect each of them to the house network with a single cable. My switch supports IEEE 802.3af but Ubiquiti uses a nonstandard PoE so I simply add the provided power injectors at the switch connections. The nodes talk directly to each other using VLAN 2.
They (or one of them) could also talk to the default LAN (no tag) and act as a router for my other computers, but I prefer not to do it that way. On both units I disable DHCP, set "LAN Mode" to NAT so it won't chew up a piece of the address space, and disable the WAN. Instead I have my main home router, which runs Debian Linux, speak OLSR natively to the two units over VLAN 2 as though it were a third Ubiquiti node. My router thus routes traffic between my home computers and either the mesh network or the regular Internet depending on destination address, acting as a NAT when necessary. Works great.

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