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100Base-T4 switch for CAT3?

Anybody able to recommend a switch or router model that'll still negotiate 100Base-T4? This is to connect two buildings via a legacy ~100' run of 8-TP CAT3 cable in a buried conduit. Currently, there's a pair of directional WLAN antennas in place. However, performance is poor and unreliable. Cutting down the trees inbetween isn't an acceptable option. So I'm exploring the feasibility of using 4-pair of the existing CAT3 cable.

On a related topic, the CAT3 is solid-core bell wire, vice stranded. Is this going make a difference? The threaded variety improves flexibility, and more conductor surface area. Is the difference going to matter?

Patrick Knott


you will need an external 100Base-T4 to 100Base-TX transceiver. I do not know any Cisco device that support this standard.

There are several things to consider here also because of the added different ground potentials.

100BASE-T4 also supports only half duplex. The problem is however to be find a suitable product.

There were once devices named Cisco Long Reach Ethernet but only 5 to 15 Mbit/s

How far apart are the buildings. Would be an option, a set of VDSL2 master / slave devices?

Ethernet - VDSL2 Master - Cat3 Cable 1 pair - VDSL2 slave - Ethernet




VDSL2 might be the right solution. Are there vendors, particular models, you can recommend?

The conduit between the two buildings is 2 inch galvanized steel pipe, about 100 feet (~30.5 meters) in length. There are no splices in the run. Only one pair of the eight was ever used. The others are clean, original pairs as the installer left them.

The buildings themselves are a bit closer than 100 feet, wall to wall. However, there are trees, gardening, etc., in between that's causing trouble for the existing WLAN solution. Also, the two ends of the conduit are in handy locations.


With just 30 m inside a large conduit one could try using the cable in place for another pull, fiber and/or cat 6, your choice. That would be the best and cheapest solution, if the cable moves.

paolo bevilacqua
Hall of Fame Master

As Patrick have pointed out, obscure ethernet varies do not seems a good idea.

Since you have multiple pairs, you can use G.SHDSL bonding for 23 Mbps

There are also wireless products designed for non-LOS enviroments, or you can elevate an antenna pole to get over the trees.

Patrick Knott


There are different manufacturers (at least in Germany). Allnet, Zyxel, ....

Search for VDSL2 Master/Slave often, pairs are offered.

But all have the same units or other enclosures, the chipset etc is the same.

Depending on the quality of the line they synchronize to appropriate speeds.

If its not enough,perhaps you can build a EtherChannel with multiple pairs.

You could also use Paolos idea.

Ethernet - Router GSHDSL - Copper Wire - Router GSHDSL -  Ethernet.

Select the best option.

If you get problems, maybe the wiring is already older that you check it galvanically (loop resistance, earth faults).



Leo Laohoo
VIP Community Legend

Do you want to consider pulling fibre optic?

It should be alot easier since there's already an existing cable.  All you need is tie the fibre optic cable in one end and pull back the copper cable.  You get more bandwidth with fibre optic.