Ohjeah!

For our access layers we primarily use Linksys/Cisco SRW2048 managed switches.  They run around $800 bucks and aside from being very reliable, have the features we need (Link Aggregation, VLAN, GB, miniGBIC).  We had an issue last week where an unknown staff member (I have an idea who), created a loop along our access layer, causing our core switches (Procurve 2848 series) to block the uplink port dropping a good portion of the network.  Thus, I decided to disable all inactive switch ports to prevent random IT staff from plugging stuff in.

While doing this I came across a switch that had not been configured for IP management, so I needed to console in to configure it.  After trying 10 different serial cables and 100 different terminal settings, I found out that the Linksys console cable (normally included with new switches) is not a null-modem or straight through serial cable.  After much searching, it appears the pins are mapped directly across:

1 – 1
2 – 2
3 – 3
4 – 4
and so on..

So I called Linksys sales, which informed me they do not sell said cable and could not send me another for free.  After hanging up I contemplated a way of building my own version and looking to see what parts I had, found 2 RJ45 to DB9 adapters.  Cutting off a 5′ chunk of Cat5 and wiring it straight through, I made my own pin to pin serial cable for the Linksys SRW2048.

If anyone is interested, the terminal settings are as followed:

Bits per second: 38400
Data bits: 8
Parity: None
Stop Bits: 1
Flow Control: None