Tuesday, May 31, 2011

CCNP home lab serial connections: T1 is the way to go!

As I'm building my home lab for the ROUTE exam, I find the DB60 DTE-DCE cables increasingly problematic, because:
  • they cost money,
  • they are bulky,
  • they are as flexible as a flagpole.
After playing around with different back-to-back connections, eBay provided the ultimate solution: WIC-1DSU-T1 cards.

They are cheaper than WIC-1T and WIC-2T cards, and use regular UTP cables (not with ethernet pinout, mind you!) for connection. Everything I need for a neat, organized rack. Only downside: they need modular routers, and can't be used with the built-in interfaces of my 1005, 1605R and 2500 series boxes.

The command to remember:

service-module t1 clock source {line | internal}
Default is line, so set one end of the link to internal.

Monday, May 16, 2011

Foundry/Brocade console cable

A few months ago I managed to buy a Foundry FWS24 switch. It comes with a DB9 serial port, but it does not work with a standard rollover DB9-RJ45 cable + RJ45-DB9 adapter combo.
Turns out it needs a straight serial cable instead of a rollover, but the built-in DB9 port is male, and I don't have female-female straight cables on hand.

At first I did an ugly hack with a DB9-DB25 modem cable, but I didn't like it very much, so I sacrificed one of my baby-blue Cisco cables, cut off the RJ45 plug on the end, and crimped a new one upside-down on it (black wire to pin 8), making it a straight cable. Using that cable and a standard Cisco DB9-RJ45 adapter (74-0495-01), the Foundry box works like a charm.

Tuesday, May 3, 2011

Linux bridge STP long path cost (802.1t-2001)

A few years ago, we had to implement STP on Linux boxes, using the long path cost standard. If changing the cost values from userspace is not really your thing, here's a patched br_if.c source (mind you, it's for an old kernel version, probably 2.6.17 or something).

Edit: for those who are interested in the actual numbers, not the Linux code: