DHCP (Dynamic Host Configuration Protocol) allows a server (in this scenario a Cisco router) to issue IP addresses to computers on the network dynamically. This is not a great solution for servers, which should have static IP addresses, but for client computers needing access to the network quickly and easily, this is certainly a great […]
Cisco routers use HDLC (High-Level Data Link Control protocol )as their default encapsulation protocol on serial lines. This works fine and there are no major problems with running HDLC however it lacks the troubleshooting commands that PPP (Point-to-Point Protocol) provides us. I learnt the value of PPP about 10 years back when I was installing […]
Two commands which are often confused or misunderstood, are the clock rate and bandwidth commands. In order to understand clock rate we first need to understand how the cabling works on routers. When connecting two routers together with a serial cable, one of the routers needs to host the DCE (Data Communications Equipment) side of […]
If you find yourself often connecting to the same devices and are looking a quicker way to telnet to them rather than constantly typing the entire IP address for each one. Or if you have a very large network and find it hard to remember every devices IP address, but you can remember the host […]
Often when typing commands in a hurry, or just typing incorrect commands, Cisco routers will try to do a lookup to find out if the invalid command is the name of another device you are trying to connect to. This results in the router displaying ‘Translating “the command”…domain server (255.255.255.255)’ three times and not accepting […]
It is important to understand that any TCP packet that is routed over a network requires bi-directional support. This means that even though I may have a route on my router to your network, if you don’t have a route back to me, the transmission of packets will fail. TCP uses acknowledgments to confirm the […]
OSPF (Open Shortest Path First) is an industry open standard supported by almost every router on the planet. OSPF is a classless routing protocol so subnetmask values are sent in the update and it supports CIDR. OSPF does not send periodic updates and is designed to only send updates when something has changed or […]
EIGRP (Enhanced Inter-Gateway Routing Protocol) is one of the fastest most reliable routing protocols available today, but it’s drawback is that it’s a Cisco proprietary protocol which means you either need a network that is running 100% Cisco, or have devices that support EIGRP in your network. EIGRP is a classless routing protocol so […]
RIP (Routing Information Protocol) was one of the first routing protocols that hit the market, and still one of the easiest to configure. RIPv1 is a classfull routing protocol and does not support VLSM’s or CIDR values and sends it’s updates as a broadcast message with a destination address of 255.255.255.255 RIPv2 supports […]
The Cisco administrative distance is a value assigned to all routing protocols to define how trustworthy the information is. If a Cisco router has multiple routes in its routing table for the same network, it looks to see which route has the lowest cost/metric value. The problem with using cost values is that different […]
The way that IP addresses have been used and allocated over the years has changed somewhat, however the principles have not changed. In order to better manage IP addresses they were put into classes and each class followed certain rules. In this post we are going to focus on the Class-full address structures, and understand […]