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I’m helping a customer improve their network through better network management visibility into network problems. The result of a proof-of-concept is this graph, which I’ll explain below. The customer loved [...]

Many moons ago, my colleague David Hailey and I put together a few quick write ups on SIP endpoints with CUCM and iPhone SIP Clients. I recently bought an Android phone (Droid Incredible) and one of the items on my list of "things to do" is testing out SIP clients…

This blog deals with a problem which was ongoing from October 2010 until February 2011.  It looks like it has finally settled down a bit (in other words a workable fix [...]

I just finished listening to a podcast where Terry Slattery was interviewed by Brandon Carroll of globalconfig.net on training tips for career certifications. If you are working on a Cisco certification, you should find that Terry's comments and advice are worth reviewing. He discusses the value of certifications and talks…

Many moons ago, my colleague David Hailey and I put together a few quick write ups on SIP endpoints with CUCM and iPhone SIP Clients. I recently bought an Android phone (Droid Incredible) and one of the items on my list of "things to do" is testing out SIP clients…

I've been thinking for a while about how to make your networks more defensible against attack. The ideas have come from digesting all that has been written in the last year or so about attacks on U.S. Government systems and Google by the Chinese government, by fraudulent electronic transfers, and…

Recently I was talking to one of my co-workers about connecting back-to-back virtual Portchannels (vPCs) from one pair of Nexus 7000s to another pair of  Nexus 7000s (or 5000s). For example, you might have a data center with lots of VLANs, and decide that while you are waiting for TRILL…

I did a Greg Ferro and The Top 25 Network Problems and Their Business Impact that I developed while at Netcordia (now Infoblox). Duplex mismatch. (See my prior article titled [...]

I recently listened to the October 10, 2010 Packet Pusher Podcast where Terry Slattery was a featured speaker. This podcast focused on network management and configuration management. Terry outlined some common network problems he has seen in supporting customer networks. Terry and other speakers Greg Ferro and Josh O'Brien discussed…

Prior to version 4.7.1 Cisco NAC would only support DES for Kerberos.  This affected the Kerberos authentication type and AD SSO authentication type.  With version 4.7.1, NAC started supporting negotiation of the encryption authentication that was used with NAC.   According to the 4.7.1 release notes, NAC can now "negotiate any…

One of my friends recently mentioned his plans to upgrade some Cisco Catalyst 6500 linecards with DFCs (distributed forwarding cards), and was wondering which DFC to use. I told him [...]

The first component of a good network management system is an event handling system. A basic event handling system can be easily implemented with open source tools like Syslog Summary [...]