When connecting a new switch to your network you can accidentally change your VLAN (Virtual LAN) database if the new switch has a higher VLAN Trunking Protocol (VTP) revision number. To avoid this, you must clear the VTP revision number on the new switch. The easiest way is to change the VTP domain name to “something_else” and back to “your_VTP_domain” on the new switch. This sets the VTP revision number to 0 and you can connect the switch ti the network without any problem. VTP version 3 has another mechanism for avoiding this problem.

Adding Comments to Access Lists

Instead of using permit or deny, simply use the remark option, for example:

console# access list 1 remark

This method works on routers and PIX firewalls. When your file has these comments you can determine exactly what certain sections were originally intended to do, which should make those long ACLs easier to understand in the future.