Chapter 4 Configuring the Router

Performing the Initial Configuration on the Router

Default Routes

A router might not be able to determine the routes to all other networks. To provide complete routing capability, the common practice is to use some routers as smart routers and give the remaining routers default routes to the smart router. (Smart routers have routing table information for the entire internetwork.) These default routes can be passed along dynamically, or can be configured into the individual routers.

Most dynamic interior routing protocols include a mechanism for causing a smart router to generate dynamic default information that is then passed along to other routers.

Default Network

If a router has an interface that is directly connected to the specified default network, the dynamic routing protocols running on the router generates or sources a default route. In the case of RIP, the router advertises the pseudonetwork 0.0.0.0. In the case of IGRP, the network itself is advertised and flagged as an exterior route.

A router that is generating the default for a network also may need a default of its own. One way a router can generate its own default is to specify a static route to the network 0.0.0.0 through the appropriate device.

Gateway of Last Resort

When default information is being passed along through a dynamic routing protocol, no further configuration is required. The system periodically scans its routing table to choose the optimal default network as its default route. In the case of RIP, there is only one choice, network 0.0.0.0. In the case of IGRP, there might be several networks that can be candidates for the system default. The Cisco IOS software uses both administrative distance and metric information to determine the default route (gateway of last resort). The selected default route appears in the gateway of last resort display of the show ip route EXEC command.

If dynamic default information is not being passed to the software, candidates for the default route are specified with the ip default-networkglobal configuration command. In this usage, the ip default-networkcommand takes an unconnected network as an argument. If this network appears in the routing table from any source (dynamic or static), it is flagged as a candidate default route and is a possible choice as the default route.

If the router has no interface on the default network, but does have a route to it, it considers this network as a candidate default path. The route candidates are examined and the best one is chosen, based on administrative distance and metric. The gateway to the best default path becomes the gateway of last resort.

SUMMARY STEPS

1.enable

2.configure terminal

3.ip routing

4.ip route dest-prefix mask next-hop-ip-address [admin-distance] [permanent]

5.ip default-network network-numberor

ip route dest-prefix mask next-hop-ip-address

 

 

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Cisco Systems OL-31454-01 manual Default Routes, Default Network, Gateway of Last Resort

OL-31454-01 specifications

Cisco Systems OL-31454-01 refers to a specific configuration guide for Cisco networking equipment, which serves an essential role in helping IT professionals understand how to deploy and manage their networking hardware efficiently. This document is particularly relevant for those working with Cisco routers and switches, highlighting various features, technologies, and best practices in network management.

A core feature of Cisco Systems OL-31454-01 is its focus on enhancing network performance and reliability. The systems typically include advanced Quality of Service (QoS) mechanisms, ensuring that critical applications receive the necessary bandwidth and performance even during peak usage times. This is crucial for enterprises that rely on uninterrupted access to applications and services.

The guide also discusses technologies such as VLANs (Virtual Local Area Networks), which allow network administrators to segment networks for improved performance and security. By isolating traffic within different VLANs, organizations can mitigate congestion and enhance overall network efficiency.

Another critical aspect of OL-31454-01 is its in-depth look at security features. Cisco networking solutions typically come equipped with integrated security protocols, such as IPsec for Virtual Private Networks (VPNs) and advanced threat detection mechanisms. This layered approach to security helps protect sensitive data from unauthorized access and cyber threats.

Furthermore, the guide emphasizes the importance of automation and programmability in modern networks. Utilizing Cisco's software-defined networking (SDN) capabilities, network engineers can automate various tasks, reducing the potential for human error and freeing up valuable resources. The integration of tools like Cisco DNA Center provides a unified network management platform, enhancing visibility and control across the entire network.

In addition to these features, Cisco Systems OL-31454-01 outlines various compatibility options with existing technologies and infrastructure. The guide ensures that IT teams can seamlessly integrate new hardware into their current networks without significant overhauls, facilitating a more efficient transition.

Overall, OL-31454-01 serves as a comprehensive resource for deploying and managing Cisco systems, offering valuable insights into essential features, technologies, and best practices that can significantly enhance an organization's networking capabilities.