Category Archives: Network

Syncing IOS Clock from Cellular Provider

I recently had a request to enable time synchronization from a Cellular provider to a 3G model of the Cisco 819. Looking through several documentation sources, I found an example of EEM policy utilizing GPS data in this manner. LTE … Continue reading

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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

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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

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Securing Your Connection Anywhere You Go

We all know that there are a lot of incomplete security models. Firesheep made this fact painfully obvious to those who regularly work from public hotspots. Although this issue extends beyond insecure wireless deployments, unencrypted hotspots are an easy target. … Continue reading

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Validation Testing Matters

A couple of weeks ago, a CLN Member Posted a question with the heading Does ASA drop active session. The specific question was as follows– I have a time based ACL configured on a Cisco ASA. I need to know if the … Continue reading

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Don’t Let Wireshark’s Assumptions Mislead Your Troubleshooting

In an effort to educate myself on the inner workings of WebEx, I recently looked at a session with Wireshark. Knowing that WebEx audio has the ability to use UDP or TCP, I wanted to isolate the protocol being employed in … Continue reading

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Using Ping Sweep to Find MTU Ceiling

Earlier this week I had breakfast with a very interesting group. One of those present had an extensive history with Cisco systems. We talked about his tenure and several of the projects that he had been involved in. For some … Continue reading

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Classic IOS as a DNS Server

There is an occasional need for a DNS server in the absence of a dedicated host. This may occur in the following situations– Using PAT, Public DNS may return a non-RFC1918 address for internal server Lab/Demo Environment Other Name Resolution challenges in SOHO, … 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

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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

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Getting the Sourcefire Firepower VM working Inline

The Sourcefire NGIPS/NGFW solution is a way to quickly get some interesting information about traffic on a network. One of the things I like about the solution is that actionable information is almost immediately available after deployment. There are five deployment … Continue reading

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