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 […]
A routing protocol is a method that routers use to share information with each other about networks they are connected to. We have seen in previous posts on this website (Creating a Static Route and Default Gateway of Last Resort) how we make routes ourselves and how to teach a router how to send packets […]
Before we can start to explain how routing protocols work, we need an understanding of wildcard masks. The concept of wildcard mask is one that many people struggle with at first, but with a little time and practice it’s becomes second nature. Converting a full class subnet mask into a wildcard mask quite straight […]
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 […]
In yesterday’s post ‘Static Routing’ we saw that we needed to create a static route to allow the Cisco router “AOIP.ORG” to ping “R2”. The static route that we created was ‘ip route 10.0.1.0 255.255.255.0 192.168.1.1’ and ping was successful to the IP address 10.0.1.2 (R2’s Serial interface). The problem with that configuration was that […]
A router by default only knows about networks that are directly connected to it. If a router is not directly connected to the final destination subnet, then the router needs to learn, or be told how to get to that destination. Learning routes can take place through the use of routing protocols, however in […]