Author Archives: Humair

OSPF Explained and Useful Troubleshooting Commands

Open Shortest Path First (OSPF) is an open standard link-state routing protocol that supports multiple equal-cost routes to the same destination (four by default). OSPF constructs a shortest path tree and then updates the routing table with the best paths. … Continue reading

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Perl – Using Pattern-sequence Memory with Regular Expressions

Pattern-sequence memory is very useful when you want to match the same character in several places but don’t care which character you match as long as all occurrences are the same character. For example, the below code matches the date … Continue reading

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Setting-up DHCP with IP Helper-Address on Cisco Routers

In a prior lab, Setting-up DHCP on Cisco Routers, I discussed how to setup a Cisco router as a DHCP server. In this lab, I use a DHCP server setup on one subnet to provide DHCP services to two different … Continue reading

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HumairAhmed.com: Top 500,000 Websites in US – Not Bad for a Blog!

Well, it looks like I’ve finally broken into the top 500,000 websites in the US in terms of traffic according to Alexa. Not bad for a semi-periodically updated blog I suppose. Most sites, especially personal blogs, don’t even make the … Continue reading

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Setting-up DHCP on Cisco Routers

The Dynamic Host Configuration Protocol (DHCP) provides the capability to automatically allocate reusable network addresses and configuration options to hosts.

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Perl – Obtain the File Size

Here is a cool one line Perl script you can use to quickly obtain the file size of a file. The syntax to run the script is “perl [scriptname] [filename]”; in the below example I use the script itself as … Continue reading

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Perl – Writing the Linux ‘cat’ Utility

The below Perl code will give you similar results compared to the Linux ‘cat’ utility. At the command prompt, just enter “perl [scriptname] [filename1] [filename2] etc …

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Perl – File-Test Operators

In Perl, file-test operators are useful for determining the status of a file. Some of the operators below refer to the “real user” which is the User ID specified at login rather than “effectve User ID” which refers to the … Continue reading

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W3C Feed Validation Service and Markup Validation Service

The W3C Feed Validation Service is a very useful tool to validate the syntax of Atom or RSS feeds. I just used it to determine why my LinkedIn WordPress application could no longer connect to my WordPress RSS feed.

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University of Berkeley Astronomers Discover Largest Known Black Holes

University of California, Berkeley Astronomers have discovered the largest black holes known to date. The black holes are estimated to be have masses equivalent to about 10 billion suns each (one black hole being slightly bigger than the other). The … Continue reading

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