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I need to hookup a business class cable modem that has 4 static IP ports to a router. In this case I am currently using an EdgeRouter 10-port which has a "PoE In" RJ45 socket.

Should I use a crossover cable to connect the modem to the router, or use a standard straight through patch cable?

Tyler Durden
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AFAIK, Since you are using relatively new devices, It doesn't really matter which cable you use. The machines will negotiate the actual parameters(bandwidth and so on) regardless of the type of cable.

Here is the another answer if you want more details, https://networkengineering.stackexchange.com/questions/34797/do-straight-though-and-crossover-still-have-any-play-in-todays-business

Ishan Jain
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  • Ok, is there any easy way to tell if a port is T568A or T568B then? The router user manual, which is pretty detailed otherwise, just says to connect it with an "ethernet cable" giving no further details on what type. – Tyler Durden Apr 08 '21 at 18:15
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T568A and T568B apply to plugs, ports do not "see" the colors of cables. Cables that have both plugs A or both B are straight and if you have A-B cable then it's crossover.
Check the specs of router and modem for Auto-MDX. If at least one of them supports it then it doesn't matter if you have straight or crossover cables. If neither supports it (which is very unlikely) then use crossover.

Sergiusz
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There is practically no gear in use today that does not support Auto MDI/-X. For the gear where it is configurable, there is practically no gear that has it turned off by default.

The only thing that a crossover cable will give you is endless headaches when you try to use it for non-Ethernet purposes and can't figure out why it doesn't work, because you forgot to explicitly label it as a crossover cable. (Remember, 8P8C connectors and "Cat X" cables are used for lots of things besides Ethernet.)

Jörg W Mittag
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