A loopback interface is a virtual interface that can be created within a network device and behaves much the same as a physical interface. Loopback interfaces can be configured on a Cisco router or a switch and have many uses. In this article, we’ll examine what they are, how they can be configured, and how […]
Comparison of Static vs Dynamic Routing in TCP/IP Networks
“Packet Routing” is the primary operation in TCP/IP networks that establishes communication from a source device located on one network to a destination device located on another network. Image Credit Within the OSI model, routing is a Layer 3 process which groups Internet Protocol (IP) data into Packets that are put inside of Frames (Layer […]
Cisco OSPF DR-BDR Election in Broadcast Networks – Configuration Example
The OSPF (Open Short Path First) dynamic routing protocol is probably the most popular and most used IGP routing protocol in TCP/IP networks. Because OSPF is supported by all networking vendors, it does not have the restrictions of proprietary protocols like Cisco EIGRP for example (in terms of multi-vendor environments etc). The new Cisco CCNA […]
How to Configure Port Forwarding on Cisco Router (With Examples)
Imagine the following situation: You are a network engineer and your boss or a customer wants you to build a cheap and easy solution to host a publicly accessible server (such as Webserver, Email server, VPN server etc) using only a regular Cisco router. In most network designs, you will see that the usual and […]
Adjusting MSS and MTU on Cisco 800 routers for PPPoE over DSL
One of the most frequent problems encountered from users of DSL internet connectivity (especially PPPoE DSL service) is when they experience incomplete connections or unreliable data transfers when they communicate with internet servers. A prominent example is when a user accesses a web site and some times it works and some times it does not. […]
The Most Important Cisco Show Commands You Must Know (Cheat Sheet)
If you are a networking professional that is operating and supporting Cisco devices and networks, then learning some important “show commands” is essential. There are a few different categories of commands on Cisco devices. There are commands that configure the device to perform a certain function and also there are commands that extract information from […]
Cisco Show IP Route Command (Routing Table)-Example and Explanation
Routing and Switching form the foundation of computer networks and the Internet in general. A network engineer must know routing principles like the back of his/her hand!! In this practical tutorial we will discuss the Cisco “show ip route” command which allows a network engineer to examine the routing table of a router device in […]
How to Configure OSPF on Cisco Routers (With Example Commands)
Open Shortest Path First (OSPF) is a routing protocol developed by Internet Engineering Task Force (IETF). OSPF is standards-based which means it is available on routers by Cisco as well as other vendors, making it a vendor-neutral routing protocol. This is in contrast to Enhanced Interior Gateway Protocol (EIGRP) that is Cisco proprietary, and hence […]
Configuring High Availability using HSRP and Boolean Object Tracking
In this tutorial we will see a special case of high availability scenario using HSRP with object tracking. Most modern enterprise networks in today’s deployments require some form of high availability depending on the uptime needed and the criticality of the service. The network infrastructure elements that are usually needed to be highly-availability include network […]
Cisco Show Interface Command on Routers and Switches Explained
One of the most useful and popular commands used on Cisco devices is the “show interface” command. It can be very useful at troubleshooting connectivity issues and physical port issues, check the status of physical ports, watch how much traffic is passing through the interface, which IP address is assigned to the interface (for Layer3 […]
Configuring GRE Tunnel Through a Cisco ASA Firewall
In this configuration tutorial I will show you how to configure a GRE tunnel between two Cisco IOS routers. One of the routers is located behind a Cisco ASA 5500 Firewall, so I will show you also how to pass GRE traffic through a Cisco ASA as well. As you might know already, GRE tunnel […]
The Protocol of the Internet – eBGP and iBGP Tutorial and Configuration
The Border Gateway Protocol (BGP) is considered to be the routing protocol of the Internet because it runs between Internet Service Providers (ISPs) to interconnect all Autonomous Systems (AS) comprising the whole internet. Of course the above refers to External BGP (eBGP) which runs between different Autonomous Systems. There is also another “flavor” of BGP […]
How to Configure Static Routing on Cisco IOS Routers (Examples)
Cisco IOS Routers support both static and dynamic routes. In small networks (2 to 5 routers) I would suggest to configure only static routes, especially if the network is not going to change much over time. Of course dynamic routing (using dynamic routing protocols such as RIP, OSPF, EIGRP) is much more flexible and scalable […]