webLOG » Cisco

Spanning-Tree topology explained

Roland — Fri, 29 Jun 2007 10:06:37 +0000

On the cisco website i found a nice presentation (i converted to PDF) about the layer 2 redundancy protocol “Spanning-Tree”. In the document there is explained, how spanning-tree works and how to protect your spanning-tree configuration in your LAN.

This is a document wich every network administrator should read

Download file: Chapter 10 – protrecting the Spanning-Tree topology

Backup Tool for Cisco Devices

Roland — Tue, 05 Jun 2007 07:40:20 +0000

Because i have a lot to do with cisco network environments, i searched for a tool, wich i can use, to backup a amount of cisco network devices quick and easy through TFTP. But i didn’t find any good tool, wich provides this feature. After a lot of research work, i deceided to write my own “Cisco Device Backup Tool”.

The basics on my tool based on a simple theory. One unique username must be configured on all cisco devices, and an easy configurable .ini file wehre i can do the main configuration and backup settings.

For my tool i used the scripting language AutoIT Script. A powerful development kit where you easily can create GUI’s, fuctions and much more things. Since version 3.2.x AutoIt even supports commands to control the Windows TCP stack.

The function of my tool is very simple. It opens a TELNET (23, TCP) socket and connect to the remote device. After a successful logon, the application set off some commands onto the device, to trigger the backup process. This would be done 1:n times, as much devices are configured in the CDB Backup configuration file (bakconfig.ini).

See Cisco Device Backup in Action:

Here you can download a clean version (V1.3.0.6) of
Cisco Device Backup (cdb_setup_v13.exe, 349KB)

Please test my tool and leave some positive or less positive commects about my tool. – Have a good time!

Befehl “ip default-gateway” unwirksam sobald Layer 3 Routing / HSRP / OSPF auf Cisco Core Switchen (3700, 6000 Series…)

Roland — Fri, 25 May 2007 11:02:33 +0000

Sobald auf einem Cisco Core Switch mit Layer 3 IP-Routing funktionalitaeten eingeschaltet werden, funktioniert das Command: ip default-gateway 12.13.14.15 nicht mehr richtig.

Es kann zu Komplikationen beim routen von TCP/IP Paketen kommen. Datenpaktete werden nur noch teilweise richtig mit diesem Befehl zum Gateway geschickt.

Abhilfe sollte schaffen, wenn man den Befehl aus der Konfiguration entfernt: no ip default-gateway 12.13.14.15

Stattdessen sollte man besser diesen IOS Befehl auf der CLI absetzen. Hier wird einfach eine statische Route zum Default Gateway gesetzt: ip route 0.0.0.0 0.0.0.0 12.13.14.15

TIPP: Wenn man das Update von Remote ausmachen moechte, sollte man erst die statische Route setzen und anschließend den no Befehl für das ip default-gateway absetzen, da man sonst nicht mehr auf das Gerät zugreifen kann….. LOGISCH ODER!