Internetwork Solutions Lessons- Understanding A Router
Internetwork solutions a complete IT networking institute which is pioneer in providing
Cisco certifications related to CCNA security training, CCNP security training, ccnp voice training, CCIE security boot camp, and prepares you for the Cisco test and CCIE exams. It is a superb institute providing dual functions as preparing for test i.e. written test and also it has a full fledged lab which provides complete training on a practical basis for CCIE training and other courses as well like
mcitp training . Internetwork solutions in its online tutorials post various articles giving a hang of IT world to the current students as well as aspiring students who want to undertake Cisco certification. In the current article Cisco expert explains what actually a router is:
We take a lot of things for granted. When it comes to technologies it is not necessarily the best idea. The point is to understand. That is why I am going to start my routing section with fundamentals. Knowing them will allow you to understand more advanced topics on your own later. Make sure you are familiar with my previous posts related to binary numbers and IP addressing before you read this and upcoming ones.
Probably the most appropriate question to start with would be ...
What exactly a router is ?
A router is a specialized computer which can connect multiple networks to allow exchange of packets between them. Since a router uses IP header information (layer 3 protocol data unit), to transmit the packets between networks, this ability makes it a layer 3 device. Like switches, routers build a special database which serves as the source of information on what to do with incoming packets. This database is formally called Routing Information Base (RIB). But most often people call it a routing table. How a router constructs a routing table and maintains information in it, will be the topics of quite a few upcoming posts.
A router is in many ways similar to a regular PC. It has RAM and ROM memory chips as well as CPU and motherboard etc. But instead of using hard drive, it uses a flash memory to store files such as the operating system (IOS). Also, what makes it distinct, the operating system and hardware are optimized for fast packet transmissions. Typically the router uses at least two interfaces but more often than not, it has a greater number of them. Cisco operating system is called Internetwork Operating System (IOS). The same name is given to OS used by many Cisco Catalyst switches. Although some of them may also use Cat OS.
There is a great variety of interfaces routers can use. For instance, they can connect few Ethernet networks together, but also Ethernet with Wide Area Networks (WANs) such as ATM, Frame-Relay, X.25, ISDN, Broadband etc.
Router Functions
In order for the routers to connect multiple layers 3 networks together; they must be able to do the following:
Understand which networks/subnets are available
In case there are multiple paths, choose the best one
Keep (routing table) must be up-to-date
Translate layer 2 headers (disparate network connections)
Keep loop-free paths
Make forwarding decisions based on layer 3 headers
Routing is primarily based on hop-by-hop paradigm. This means that if there are multiple routers in the path, a router must find the outbound interface and forward the packet to a next hop router. A router could not care less as to what happens to the packet after it has been expedited.
In order to find the outgoing interface an IP destination address of a packet and a routing table are used. The process whereby destination IP address is the key information to find the outbound interface for a packet is called destination-based routing. However, it is possible to influence that decision making process and choose other criteria such as source of IP transmission, size of the packet, importance of the packet in relation to others or some other parameters rather than destination IP address. When used it is referred to as the traffic engineering. For now though, I am going to focus in on the default behaviour.
by: Daniel
Internet Marketing In Japan An Effective Technique Anonymous Proxy For Privacy Protection From Internet Cookies As Well As, Web Bugs Promoting Your Services Through Internet Marketing Cash Advance Loans Internet Based * How To Find Legit On The Web Advance Loan Lenders Avoiding Finan Everyday Deals Via The Internet Boost Your Brand Potential Through Internet Marketing Importance Of Directory Submission In The Internet Marketing Plans Internet Marketing Communication At&t Managed Internet Services With Dedicated Internet Access Connection Time To Answer The Big Questions Over Children Using The Internet Payday Via The Internet And How You Can Find Reputable Online Payday Loan Financial Institutions And Steps For Making Logo Design On Internet Web Promotional Unique Codes Offer Affordable Internet Access For Everyone