Remember the old management adage "You can only manage what you can measure"? Well, there's a corollary in Network Management, in which you can only manage devices that you know to exist. In my current job, the network has over 600 core network devices (e.g. routers and switches) and in...

How do you monitor the critical components of your infrastructure? Let's say that your core consists of 75 key devices, plus the links that interconnect them. It makes sense to monitor device status as well as the links between them. If each system has three or four links, that means that you have...

"Holy Crap!" exclaimed David from the depths of the cube farm, "We just failed the PCI audit! Check out the email from Tony." Tony is the CIO. David is one of my co-workers, a good friend, and overall smart guy. I turned to my email and checked out the message. Sure enough, the Payment...

It is configuration checking time. Do you know where all your devices are? How do you know that there's not a rogue device lurking in your network? How do you know that the configuration collection mechanism has discovered all the devices in your network? I just finished working on a security assessment...

I recently received a comment from Gerry Gerofsky about IPv6 network discovery: Hi Terry, I am trying to understand how CiscoWorks, OpenView discovers an IPv6 network? In Ipv4, typically a tool like OpenView CiscoWorks, you feed it a subnet and it goes and checks all the IP's. What is available in...

I discovered a patent application (not yet granted) this week that gave me chills. Part of its claims* are performing Layer 2 and Layer 3 network topology discovery and display, as of October 2001. Huh? Network topology discovery and display was being done way before then. What's chilling about this...

I had the privilege of reviewing a neat paper, Network Topology Discovery , by Eric Siegel, a technical analyst at the Burton Group. His paper covers a many aspects of network topology discovery in 30 pages, sprinkled with details on how things work. I found it to be a very well written paper, covering...

Visualization of networks has been something that I've been watching for some time and have yet to see anything that looks really interesting. Many vendors use the Tom Sawyer Software package. Netviz had an interesting package but CA (which acquired them via their Concord acquisition) decided to...

I am regularly surprised by network redundancy designs that are either overbuilt or underbuilt. There seem to be two major themes that drive these designs. I'll address the first theme in this blog entry and the second theme in a successive blog entry. The first theme results in a network with excessive...

One of the security factors I’ve heard espoused about IPv6 is that the large address space (128 bits: 64 bits of network and 64 bits of host address) makes it impossible to scan the network for hosts. On initial inspection, this seemed like a reasonable thought. However, when you look at IPv6's...