Using the Cisco IOS Archive Command
The Cisco IOS archive command is not only very useful in keeping configuration archives, but it can also be used to log commands entered into the router, along with their user …
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Introduction to Private VLANs
The concepts behind Private VLANs are in fact rather simple, but it is quite easy to get discombobulated in the details. In their simplest form, PVLANs can dissociate ports within …
Read MoreBidirectional Forwarding Detection
Bidirectional Forwarding Detection (BFD) is a UDP-based protocol that provides fast (very fast!) routing protocol independent detection of layer-3 next hop failures. BFD can be …
Read MoreMeasuring Cable Lengths on a Catalyst Switch
A while back, I was playing on a 3750 switch in a customers lab and came across something I’ve never seen before. It seems that some Cisco switches have a built in Time-domain …
Read MoreUsing Discontiguous Wildcard Masks in ACLs
Unlike subnet masks, wildcard masks allow you to use discontiguous bits which enable you to match on a range of values. Using these within routing protocols is typically frowned …
Read MoreUsing Regular Expressions on Cisco IOS
As a followup to my previous post on Regular Expression Basics , I wanted to give a few examples on using them on Cisco …
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