Routers are networking devices that forward data packets between different networks. Routers use header information and forwarding tables to determine the best path between networks, and protocols like ICMP to communicate with each other. There are software and hardware routers, with hardware routers like Cisco routers providing better performance. Static and default routing involve manually configuring routing tables, while dynamic routing allows tables to change automatically as network routes change.

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ROUTING
A device that forwards data packets along networks. A router is connected to at least two networks,
commonly two LANs or WANs or a LAN and its ISP’s network. Routers are located at gateways, the places where
two or more networks connect.
Routers use headers and forwarding tables to determine the best path for forwarding the packets, and they use
protocols such as ICMP to communicate with each other and configure the best route between any two hosts.
Very little filtering of data is done through routers.
Types of Routers
Software Router (Windows ) Hardware Router (CISCO)
1.Routing Scenarios Using Single Router
Steps to Activate the System as a Router :
Start - Programs - Administration Tools - Services-
Select – Routing and Remote Access - Start the service
2.Routing Scenarios using Double Router

2. Tpes of Routing
1.Static Routing
2.Default Routing
3.Dynamic Routing
1.Static Routing
Static Routing, is the process in which the system network administrator would manually configure network
routers with all the information necessary for successful packet forwarding. The administrator constructs the routing
table in every router by putting in the entries for every network that could be a destination. Static routes to network
destinations are unchangeable
Simple Scenario for Static Routing Table for Double Routing :
Routng Table for Router 1 Routing Table For Router 2
Interface LAN2 Interface LAN3
Destination Network 30.0.0.0 Destination Network 10.0.0.0
De Destination Mask 255.0.0.0
Destination Mask 255.0.0.0 D Default Gateway 20.0.0.2
Default Gateway 20.0.0.1
Default Routing

3. A default route, also known as the gateway of last resort, is the network route used by a
router when no other known route exists for a given IP packet's destination address. All the
packets for destinations not known by the router's routing table are sent to the default route. This
route generally leads to another router, which treats the packet the same way: If the route is
known, the packet will get forwarded to the known route. If not, the packet is forwarded to the
default-route of that router which generally leads to another router. And so on. Each router
traversal adds a one-hop distance to the route.
Once the router with a known route to an host destination is reached, the router determines which
route is valid by finding the "most specific match". The network with the longest subnet mask
that matches the destination IP address wins.
Simple Scenario for Default Routing Table for Double Routing :
Routng Table for Router 1 Routing Table For Router 2
Interface LAN2 Interface LAN3
Destination Network 0.0.0.0 Destination Network 0.0.0.0
De Destination Mask 0.0.0.0 Destination
Mask 0.0.0.0 D Default Gateway 20.0.0.2
Default Gateway 20.0.0.1
Dynamic Routing
Dynamic routing performs the same function as static routing except it is more robust. Static
routing allows routing tables in specific routers to be set up in a static manner so network routes
for packets are set. If a router on the route goes down the destination may become unreachable.
Dynamic routing allows routing tables in routers to change as the possible routes change. There
are several protocols used to support dynamic routing including RIP and OSPF