In this post, I am going to configure Survivable Remote Site Telephony (SRST) between CUCM (site A) and a cisco router 2911 (Site B) for a call processing backup mechanism that allows IP phones to register when a WAN link is disconnected. Assume that the WAN link goes down, Cisco IP phones at site B should register to […]
Domain Name Service (DNS) As we covered in our networking course here, in order to send your message to a destination over a routed infrastructure, you need to encapsulate your message into a TCP/IP Layer-3 header. We have also covered that headers include source and destination addresses. In case of Layer-3 with TCP/IP model, we […]
tcpdump tcpdump is a text-based network sniffer. Let’s capture some traffic. We have used switch -i to indicate the interface on Kali Linux which we want to sniff on. Then we have specified our filer to match the traffic. If we don’t specify any filter, we capture all the traffic passing through that interface. The […]
hostnamectl and timedatectl To query and change the system hostname and related settings use hostnamectl command. timedatectl may be used to query and change the system clock and its settings, and enable or disable time synchronization services. ip vs ifconfig Ethernet networks are called ethx (old fashion) or things like enp0s25 (nowadays). Traditionally, ifconfig was the tool to configure […]
Netcat (nc) Netcad is installed by default on your Kali Linux. It is according to its man page is TCP/IP swiss army knife. It is a simple unix utility which reads and writes data across network connections, using TCP or UDP protocol. Netcat can run in client or server mode. Netcat in client mode In […]
wget wget is a utility for download of files from the Web. It supports HTTP, HTTPS, and FTP protocols. curl curl is a tool for transferring data from or to a server. It supports these protocols. Switch -o along with a string saves the file under the name of that string. As an exercise download […]
process status (ps) The command ps lists processes system-wide. This is one of your main tools to understand what software is running on the system. The main switches are: e to select all processes f to display full format listing (UID, PID, etc.) l to display in long format Finding your SSH process in the […]
In this article we are going to talk about The Port-Security feature in Cisco Switches, which is a Layer 2 First Hop Security Mechanism. Port-Security Port-Security is a feature on Cisco Layer 2 and Multi-Layer Switches (MLS), which in simple words, it is helping us to limit the number of MAC addresses that the device […]
Regular Expressions A Regular Expression (regex) is a text string which describes a pattern to find text. You can visit https://www.regular-expressions.info/tutorial.html to learn more about Regular Expressions. However, I will teach you the minimum you need to take from this course. Literal Characters Consider This is a test. sentence. Consider the most basic regular expression […]
At this point, I prefer to present my networking students a practical tool which Floods CAM Table of a Cisco Catalyst switch. It is unrelated to the previous and next posts. macof The command macof is the tool with which we are going to flood a LAN switch (In our example a Cisco Catalyst switch) […]
Elissa Garlin
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