Category Archives: Certification

Internet Redundancy with ASA SLA and IPSec

I’ve seen a lot of examples of redundant Internet connections that use SLA to track a primary connection. The logic is that the primary Internet connection is constantly being validated by pinging something on that ISP’s network and routing floats … Continue reading

Posted in CCIE Security, CCNA Security, Certification, Security, Technology | Tagged | 6 Comments

CLN 2015 Designated VIPs

I wanted to take a moment and give a well-deserved congratulations to the 2015 Cisco Learning Network Designated VIPs. These fine folks spend a ton of time giving back to the community by helping others in their learning process. New … Continue reading

Posted in Blogroll, Career, Certification, General, Technology | Tagged , , | 4 Comments

Discard Routing for RFC1918 Addresses

While working with firewalls for the last few years, I’ve seen many logs polluted with scanning traffic. Obviously this is the type of thing that I want to see when someone is legitimately scanning, or attempting to scan, through the firewall. However, … Continue reading

Posted in CCIE Security, CCNA Security, Certification, General, Network, Technology | Tagged , | 2 Comments

The Longest Match Rule

One of the the concepts that comes up occasionally is that of precedence. For example, one might consider the following routing table entries. ip route 0.0.0.0 0.0.0.0 1.1.1.1 //default route ip route 192.168.0.0 255.255.0.0 1.1.1.2 //supernet/cidr route ip route 192.168.1.0 255.255.255.0 … Continue reading

Posted in CCNA, Certification, General, Network, Technology | Tagged | 3 Comments

Native TFTP and FTP Server in OSX

As a System Engineer, I do occasionally have to do real field work. When that happens, having access to a TFTP and FTP server is sometimes required. Although the [lack of] UI makes the use counterintuitive, these tools are available in OSX. This … Continue reading

Posted in Certification, General, Network, Technology | Tagged | 3 Comments

Forming a Thought Process for Troubleshooting

Periodically, I get a message from someone asking for troubleshooting help. The most recent of these went something like the following (paraphrasing)– I have the following routers, R1 through R5, and I cannot ping R5 from R1. Please tell me … Continue reading

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IP Subnetting Part 5: Subnetting Across the Octet Boundary

Throughout this series, we have examined several fundamental building blocks of subnetting. In IP Subnetting Part 4, we looked at what was required to subnet a Class C network. This article takes the fundamentals one step further and looks at … Continue reading

Posted in CCNA, Certification, General, Network, Technology | Tagged , , , , | 3 Comments

Using NVI to Allow Internal Hosts to Connect to Public Addresses of Hosted Servers

IP NAT is a very common configuration. One of the challenges that sometimes surfaces is the need for internal hosts to connect to the public address of a locally hosted server. Anyone who has tried to configure something like the following has … Continue reading

Posted in CCNA, Certification, General, Network, Security, Technology | Tagged , , , | 8 Comments

IP Subnetting Part 4: Subnetting a Class C Network

At this point in the PacketU subnetting series, we have worked through the following– What is a Subnet? Simple Subnetting Examples Understanding the Binary This article takes the concept of subnetting to the next step. Today we are going to look at … Continue reading

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Explanation: TunnelX temporarily disabled due to recursive routing

I wanted to take a few minutes to share a scenario that some seem to struggle with. This scenario is a routing issue that sometimes occurs when an interior routing protocol allows routes to leak back through a tunnel. To … Continue reading

Posted in Certification, General, Network, Technology | Tagged , | 4 Comments

IP Subnetting Part 3: Understanding the Binary

I’ve often stated how simple subnetting really is. While each individual concept is rather simple, it is the combination that make the holistic process challenging. If we, as humans, could look at the process more like computers and network devices, … Continue reading

Posted in CCNA, Certification, General, Network, Technology | Tagged , , , , | 1 Comment

Using Cisco’s DevNet “All-in-One VM” as a Free Router Lab

I know many have been [not so patiently] waiting for the arrival of a Cisco virtual lab. Although I haven’t heard any official release date for VIRL or CML, there is a small scale virtual router lab available today. This lab is … Continue reading

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