Sunday, June 14, 2009

DB9 - RJ45 Serial Pinouts

I frequently use serial connections for access to network devices. I find it a hassle to carry around the old serial cables... especially with limited space in my bag. On the other hand, I always have a few cat 5/5e cables handy. I decided years ago to just start using the DB9 to CAT5 adapters you can get at places like Radio Shack.

I labeled these pinouts A and B, but those names are arbitrary. You'll find that layout B is most commonly used in the blue cisco cables... particularly the older cables that had a separate connector. In both cases, the green wire is optional (and is soldered to the red wire, at least in the Cisco version) - at least with all the network gear I've worked with in the last few years. Also, pins 1 and 9 aren't used in either version.

The advantage of these two are that you need only two of these adapters (one of each) and a cat 5 or cat 5e cable.

If you need to connect to a piece of Cisco gear (they typically use the RJ45 serial port,) just use the type A connector and a cat5 cable direct to the Cisco box.

If you need to connect to a piece of gear that uses DB9, place one connector on each end of the cat 5 cable.

typePin 1Pin 2Pin 3Pin 4Pin 5Pin 6Pin 7Pin 8Pin 9
xblackyellowbrownred (+green)orangewhitebluex
Bxyellowblackorangered (+green)brownbluewhitex

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