Basic Router Concepts

What is a Router?

A router is a device that forwards traffic between networks based on network layer information in the data and on routing tables aintained by the router. In these routing tables, a router builds up a logical picture of the overall network by gathering and exchanging information with other routers in the network. Using this information, the router chooses the best path for forwarding network traffic. Routers vary in performance and scale, number of routing protocols supported, and types ofphysical WAN connection they support.

Routing Information Protocol

One of the protocols used by a router to build and maintain a picture of the network is the Routing Information Protocol (RIP). Using RIP, routers periodically update one another and check for changes to add to the routing table. RIP-2 supports subnet and multicast protocols. RIP is not required for most home applications. 

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Security in Network

What is IT-Security?

IT-Security is not a product, it's a process. Don't think to buy a firewall which solves all your security problems! You always have to ensure good configuration and updates - this should be an integrated process. But you never will reach 100% of security, it's like a bank safe: you can make it difficult to crack, but there will always be somebody, who is able to break it with a lot of resources! Here are the most important components of IT-Security:

Authenticity

Authenticity is about the identity of a subject/object. This can be a user, a process, a system or an information. This is needed for Non Repudiation and Accountability.

Integrity

This means Data-Integrity, that data was not manipulated or destroyed in an unauthorized way and System-Integrity, that the system is available with the usual performance and was not manipulated with unauthorized access. Integrity is part of Authenticity.

Confidentiality

Information should not been seen by unauthorized persons, instances or processes. This means protection of personnel or business-critical data, privacy and anonymity.

Availability/Dependability

Refers to functionality of soft- and hardware ist not altered in any unauthorized way and about secured business continuity.

Non Repudiation/Accountability

Non Repudiation means, that actions of instances (users, processes, systems and information) can be associated with only that instance. Accountability refers to financial transactions and all communication issues.

Reliability

The usual functionality and behavior of data and systems is secured. This is needed for Integrity and Non Repudiation.

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Understanding Static and Default Routes

Static routes are useful in stub networks in which we want to control the routing behavior by manually configuring destination networks into the routing table:

Router(config)#ip route 10.0.0.0 255.0.0.0 192.168.2.5

A floating static route can be configured when redundant connections exist and you want to use the redundant link if the primary fails. This is configured by adding a higher administrative distance at the end of a static route:

Router(config)#ip route 10.0.0.0 255.0.0.0 192.168.2.9 2

A default route is a gateway of last resort for a router when there isn’t a specific match for an IP destination network in the routing table (such as packets destined for the Internet):

Router(config)#ip route 0.0.0.0 0.0.0.0 serial 0/0

With routing protocols, you can specify a default network, which is a network in the routing table that routing devices consider to be the gateway of last resort. Using their routing protocols, they determine the best path to the default network:

Router(config)#ip default-network 192.168.1.0

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Static and Dynamic Route Comparison

Routers can forward packets over static routes or dynamic routes based on the router configuration. The two ways to tell the router where to forward packets to destination networks that are not directly connected are as follows:

■ Static route: The router learns routes when an administrator manually configures the static route. The administrator must manually update this static route entry whenever an internetwork topology change requires an update. Static routes are user-defined routes that specify the path that packets take when moving between a source and a destination. These administrator-defined routes allow very precise control over the

routing behavior of the IP internetwork.

■ Dynamic route: The router dynamically learns routes after an administrator configures a routing protocol that helps determine routes. Unlike the situation with static routes, after the network administrator enables dynamic routing, the routing process automatically updates route knowledge whenever new topology information is received. The router learns and maintains routes to the remote destinations by exchanging routing updates with other routers in the internetwork.

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