System Notes Org

Discover the Switch Port to which the Server is Connected A previous article, Advanced Linux Networking Tools , covered the basic usage of tcpdump and tshark to discover switch ports on a Cisco switch, but there are times a system may be connected to a different brand, or using a different protocol.  Also, wireshark is not always installed, so relying on tshark is not always the most convenient way to get the required info. By default, Cisco uses a proprietary method of communication between switches and routers called Cisco Discovery Protocol (CDP).  There is another protocol called Link Layer Discovery Protocol (LLDP), which used by other brands, so it is useful to list other options. Find switch information First, use ifconfig to find the interface names.  Then, use tcpdump to listen for packets.  Optional:  write the packet capture output to a .cap file, and use tshark to read the output. Cisco Discovery Protocol (CDP) YOUR_INTERFACE=eth0 ...

Here are a few notes to add to the previous article on ping. This time, we look at some bash one-liner tips and tricks. Combine multiple commands Return Values Ping Multiple Hosts Using Bash Nmap and Fping Ping, and Command Line Variables Start from the beginning. We want to see what happens when attempting to ping a host that resolves an IP address from DNS, but is not reachable from our network at the moment. This is to show how we might build a simple monitoring tool from scratch, and also to see what kind of fun we can have with the command line. To ping a host only one time use the count option, which in Windows is -n, and in Linux is -c. Windows C:\>set host=google.com C:\>ping -n 1 %host% Pinging google.com [216.58.219.46] with 32 bytes of data: Request timed out. Ping statistics for 216.58.219.46: Packets: Sent = 1, Received = 0, Lost = 1 (100% loss), Bash: Linux, Mac, Unix Note that in bash, we don't use the set command to assign a varia...

When attempting to learn new tools, such as git, or vim, it is easy to get lost in all the features.  Here is a quick start guide that focuses on the essentials for a single user to get started with a local git repo.  Working with a team, and advanced features can be added later. Git Quick Start Commands Git Core Commands git init git add . git commit -m “initial commit” Supporting Commands git status git log Remote Repository Commands git clone [url] git pull git push Git Notes on github goes into more detail https://github.com/systemnotes/gitnotes