Mark J. Lewis


The Trouble with IPsec VPNs, Part#3: IKE Phase 1 Success

I have surfaced again after a busy few weeks - and I can finally continue my description of IPsec VPN troubleshooting (sorry about the delay). This time I'll take a closer look at IKE Phase 1 (main mode) troubleshooting.Before...

The Trouble with IPsec VPNs, Part#2: Methodology

A while back, I started blogging on the subject of IPsec troubleshooting. In that blog post, I mentioned that in order to successfully troubleshoot IPsec in a fast and efficient manner it is necessary to have a good knowledge of how...

Cisco Telepresence: Pretty Spooky…

A while back I had my first experience using a Cisco Telepresence system (3000), and I thought that I would share some thoughts.My overall impression is that it is pretty spooky (at least the first time you use it). Sat there...

Brocade Buys Foundry: Good Idea?

So, Brocade has bought Foundry. I may be wrong, but to me it looks like these companies have gazed into the future, not liked what they have seen, and jumped into each other's arms out of fright!Personally, I think that Cisco are...

The Trouble with IPsec VPNs, Part#1

Depending on their size and configuration, IPsec VPNs can be relatively easy to design and deploy, even if you are not all that knowledgeable about how IPsec actually works. But, if you don't understand how IPsec works and you don't...

CCIE Voice / CCVP Exam Objectives #7: RTP and cRTP

While protocols like MGCP, SIP, H.323 (H.225/H.225 RAS/H.245), and SCCP provide signalling in VoIP/IP telephony/unified communications networks, the Real Time Transport Protocol (RTP) is used to transport the voice and video media...

Catalyst 6500: The End Isn't Nigh...

Since Cisco launched the new Nexus range of switches, quite a number of people have asked me whether the advent of the Nexus switches heralds the demise of the Catalyst 6500. Furthermore, I have heard that some of Cisco's competitors...

CCIE Voice / CCVP Exam Objectives #6: SCCP

Last time in this series of posts on telephony protocols, I looked at H.323, a complex framework of standards and protocols that are used to enable multimedia communication over packet networks. This time I'll be taking a look at a...

Hands on with the Cisco Nexus, Part#2: Virtualization

Note: if you have been following my series on CCIE Voice / CCVP Exam Objectives, and are wondering why that series has stopped, don't worry because it hasn't. I'll be alternating between subjects over the next few weeks and months -...

CCIE Voice / CCVP Exam Objectives #5: H323 Messages (Cont.)

In my previous blog post, I described the most important H.323 protocols, standards, and network elements. This time I'll be taking a look at how those network elements communicate.As mentioned last time, H.225 RAS allows...

CCIE Voice / CCVP Exam Objectives #4: H.323

So far in this series I have described two telephony protocols (SIP and MGCP) that feature prominently on the CCIE Voice and CCVP exam blueprints. In this blog entry, I am going to describe another, H.323.H.323 is a collection or...

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