Mark J. Lewis

CCIE Voice/CCVP Objectives #3: Media Gateway Control Protocol (MGCP)

A telephony protocol that features prominently in the CCIE Voice and CCVP exam blueprints (as well as the real world!) is the Media Gateway Control Protocol (MGCP). MGCP is a master-slave protocol that involves a Media Gateway...

CCIE Voice/CCVP: Telephony Protocols - SIP Messages

Last time I gave a high level overview of SIP and also took a look at SIP network element types. This time, I'll be looking at SIP message and method types, and describing how SIP network elements communicate. If you can't remember...

CCIE/CCVP Voice: Understanding Telephony Protocols

Since I posted on the subject of passing the CCIE Voice exam, I have had a number of requests to blog some more on some of the individual CCIE Voice exam objectives. So, in response to these requests, I'll be posting on these...

Nexus: Hands on with NX-OS, Part#1

Since Cisco announced the Nexus 7000, I have seen and heard quite a lot of criticism of NX-OS, often on the basis that it will force engineers to learn a whole new CLI. But Cisco believe that NX-OS is ‘IOS-like', and that engineers...

Configuring an L2TPv3 Ethernet Pseudowire

As I mentioned last time, L2TPv3 has a plethora of capabilities, including the capability to be used for remote access VPNs, the capability to transport a number of Layer-2 protocols in a pseudowire configuration, the capability to...

L2TPv3 Pseudowhat?

L2TPv3 has been around for a while now, but it seems to be one of those things that not too many people know about.Typically, when I raise the subject of L2TPv3, I get one of the following reactions:‘L2TPv3 pseudowhat?'‘Nobody uses...

Cisco vs. Juniper Episode II: Enterprise Switching

I don't know if anyone noticed, but Cisco and Juniper announced some new switches a few days ago. Anyway, Network World has asked me to comment on these switches, so here are some initial thoughts.Cisco and Juniper have been going at...

How to pass the CCIE Voice written exam

Well, I’ve finally resurfaced after a hectic few weeks (sorry about the delay).The nice people at Network World have persuaded me - I’m here to stay! As I rove from client site to client site and deal with a variety of technical...

Choosing the Right Remote Access VPN: 9 Important Questions

Last time I looked at some important questions to ask when selecting a site-to-site VPN protocol or technology. This time I will discuss some the important questions to ask when choosing a remote access VPN. A remote access VPN...

Which Site-to-Site VPN: 10 Important Questions

One of the most common questions that I am asked is what type of VPN an organization should deploy. So, in the hope that it will save some people some time, I thought I’d just go through some of the most basic considerations when...

Preventing IPsec VPN failures: recommendations (part 2)

In my last blog post, I recommended a number of ways to avoid the first five of my top ten reasons why IPsec VPNs fail. As promised, in this blog post, I'll finish this particular topic by explaining how to avoid the final five in...

Preventing IPsec VPN failures: recommendations (part 1)

Well, based on a number of emails I have received, some people were quite surprised to learn in my first blog post that poorly designed and configured IPsec VPNs are vulnerable not only to the NSA and GCHQ, but also to pretty much...

Top 10 reasons why IPsec VPNs fail.

As an independent consultant, I am often asked to be a ‘fresh set of eyes’ and perform a network assessment. This sometimes involves an examination of an IPsec VPN.During discussions around an IPsec VPN deployment, I occasionally...

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