What is a Router:-

The router, at least the common home network device that is usually called a router, is the piece of network hardware that allows communication between your local home networks—like your personal computers and other connected devices.

The router is a physical or virtual internetworking device that is designed to receive, analyze, and forward data packets between computer networks. A router examines a destination IP address of a given data packet, and it uses the headers and forwarding tables to decide the best way to transfer the packets.

What is ACL(Access Control List)

Router Choose the Best Path

• Routers use static routes and dynamic routing protocols to learn about remote networks and build their routing tables.
• Routers use routing tables to determine the best path to send packets.
• Routers encapsulate the packet and forward it to the interface indicated in the routing table.

Router Forwarding Methods

• Process switching – An older packet forwarding mechanism still available for Cisco routers.
• Fast switching – A common packet forwarding mechanism which uses a fast-switching cache to store next-hop information.
• Cisco Express Forwarding (CEF) – The most recent, fastest, and preferred Cisco IOS packet-forwarding mechanism.

Configure Router Basic Settings

• Name the device –Distinguishes it from other routers
• Secure management access – Secures privileged EXEC, user EXEC, and Telnet access, and encrypts passwords.
• Configure a banner –Provides legal notification of unauthorized access.
• Save the Configuration

Configure an IPv4 Router Interface

To be available, a router interface  must be:

• Configured with an address and subnet mask.
• Activated using no shutdown command. By default, LAN and WAN interfaces are not activated.
• Configured with the clock rate command on the Serial cable end labelled DCE.

Configure an IPv6 Router Interface

Configure interface with IPv6 address and subnet mask:

• Use the ipv6 addressipv6-address/ipv6-length [link-local | eui-64]interface configuration command.
• Activate using the no shutdown command.

IPv6 interfaces can support more than one address:

• Configure a specified global unicast – ipv6address ipv6-address/ipv6-length
• Configure a global IPv6 address with an interface identifier (ID) in the low-order 64 bits  – ipv6address ipv6-address/ipv6-length eui-64
• Configure a link-local address – ipv6address ipv6-address/ipv6-length link-local