Tech Tip

To get router console messages sent to the syslog daemon on a UNIX management machine, configure:

logging a.b.c.d

where a.b.c.d is the address of the management system. Control the level of messages sent by configuring

logging trap level-word

where level-word is the Cisco keyword for severity level. Traps at the specified severity level (or worse) are sent.

To get console messages from a router as SNMP traps (for example, when managing with a PC running NT, with no syslog daemon), configure:

snmp-server enable traps syslog

Optionally:

logging history 6 (sets the severity level)

logging history size 500 (maxes the SNMP table size, for console messages retained by the router)

TIP: Redundant Power Supplies -

If you have redundant power supplies, ensure they are different electrical circuits. That way if one circuit fails, the other circuit will still provide power to your router.

Ideally, your electrical outlets have isolated grounds, meaning they are wired directly to ground. In VA, this means the outlets are orange in color. This helps, but won't stop a voltage spike. You will still need a surge suppressor to prevent voltage spikes from damaging your equipment. (Ask us how we know this!!!)

TIP: A Server On Your Local Wire -

Configure it with a tftp server, a bootp server, and a syslog server. The tftp server makes it easier to do code upgrades and configuration saves. The syslog service keeps a good record of system activity. The bootp server will help if you ever have equipment that loses its configuration and needs a way to dynamically relearn its configuration information. You want to build the bootp server before you need it!!!! It's a pain to do when you're under the gun!! Put FTP on the system too, so you can get the upgrade code from Cisco when you need it.

Tech Tip: Way Cool Catalyst Spanning Tree Hacks

The new 3.1 Catalyst NMP code is out, and it includes Cisco's long-awaited 'Spanning Tree Optimization" called 'UplinkFast', as well as 2 other surprise STP improvements.

See the URL's at the bottom for Cisco references in the documentation.

I'll briefly summarize:
UplinkFast, as we probably all expected, takes advantage of certain topology restrictions to reduce STP failover times to about 3 seconds. It takes advantage that the fact that if it is the ROOT PORT that fails, it can quickly select another root port. It will then instantly flip all of the CAM table entries to reference the new root port AND then start sending special notifications to the upstream neighbor to update it's CAM table (for the affected MAC addresses and VLANs). To enable the feature, enter "set spant uplinkfast enable [rate <]. The final optional parameter controls how fast the previously mentioned updates are sent to the upstream neighbor (so as not to overwhelm it).

The topology requirements appear to be:
1) root bridge not in access layer (wiring closet switch)
2) 2 links from access layer (wiring closet) to distribution layer "show spant uplinkfast" to view current settings.
It appears to work in conjunction with "set spant root" and "set spant portvlancost" (see both below) to automatically tweak bridge priorities and path costs.

Tech Tip: Utilize Your AUX Port

You can use your aux port on the Cisco router for a couple of purposes.

1. Get ISDN dial-up access into a Cisco router without an ISDN line. This is a stopgap measure until you get native ISDN, but you'll need a Terminal Adapter (TA), of course. You can get speeds of up to 38,400 from the aux port.

2. Use the aux port as another routable port, as a stopgap, if you need a DDR port and have used up all your existing ports.

3. Hook a dial-in analog modem to the aux port so you can troubleshoot a router that is causing problems.

Be aware that each character over the aux port generates a CPU interrupt, so excessive AUX traffic can potentially degrade the performance of the router....which is why it's a stopgap routing port.

Volume 4 Number 1 Table of Contents