Cisco Router Dynamic Routing Protocols

Dynamic Routing Protocols

• Cisco ISR routers support various dynamic IPv4 routing protocols, including EIGRP, OSPF, IS-IS, and RIP.
• Cisco ISR routers also support dynamic IPv6 routing protocols, including RIPng, OSPF v3, EIGRP for IPv6, and MP-BGP4.

Static Routing

• Routers can learn about remote networks through manual or dynamic configuration.
• Static routes are manually entered into the route table, providing better security and using less bandwidth.
• Static routes have a fixed path and do not require CPU cycles for calculation and communication.
• However, static routing has disadvantages, including time-consuming initial configuration and maintenance, error-prone configuration, and the need for administrator intervention.

Why Use Static Routing?

• Static routing provides advantages, including better security, reduced bandwidth usage, and fixed path determination.
• However, static routing has disadvantages, including time-consuming initial configuration and maintenance, error-prone configuration, and the need for administrator intervention.

When to Use Static Routes

• Static routing is suitable for smaller networks that are not expected to grow significantly.
• Static routing is used for routing to and from stub networks, which are networks accessed by a single route.
• Static routing is used to create a single default route to represent a path to any network that does not have a more specific match with another route in the routing table.

Types of Static Routes

• Static routes can be used to connect to a specific network, provide a gateway of last resort for a stub network, reduce the number of routes advertised by summarizing several contiguous networks, and create a backup route in case a primary route link fails.
• Default static routes are used to send traffic to any destination beyond the next upstream router.
• Default static routes are configured with a destination IPv4 address of 0.0.0.0/0.
• Summary static routes are used to reduce the number of routes advertised by summarizing several contiguous networks.
• Floating static routes are used to provide a backup path to a primary static or dynamic route in the event of a link failure.

Configure IPv4 Static Routes

• The next hop can be identified by an IP address, exit interface, or both.
• There are three types of routes: next-hop route, directly connected static route, and both.
• Administrative Distance is the "trustworthiness" of the route, with lower values indicating higher trustworthiness.

The Routing Table

• The routing table is a file stored in RAM that contains information about directly connected routes, remote routes, and network or next hop associations.
• The show ip route command is used to display the contents of the routing table.
• Routing table sources include link local interfaces, directly connected interfaces, static routes, and dynamic routing protocols.

Directly Connected Routes

• A newly deployed router without any configured interfaces has an empty routing table.
• An active, configured directly connected interface creates two routing table entries: Link Local (L) and Directly Connected (C).

Statically Learned Routes

• Static routes are manually configured and define an explicit path between two networking devices.
• Static routes must be manually updated if the topology changes.
• Benefits of static routes include improved security and control of resources.
• The syntax for a static route to a specific network is ip route network mask {next-hop-ip | exit-intf}.
• The syntax for a default static route is ip route 0.0.0.0 0.0.0.0 {exit-intf | next-hop-ip}.