Dynamic Routing

Dynamic Routing

1. Dynamic Routing Protocols

   • Dynamic Routing Protocol
     • Components
       • Data structures
       • Routing protocol messages
       • Algorithm
     • Purpose
       • Discovery of remote networks
       • Maintaining up-to-date routing information
       • Choosing the best path to destination networks
       • Ability to find a new best path if the current path is no longer available
   • Dynamic Versus Static Routing
     • Static Routing
       • Uses
         • Providing ease of routing table maintenance in smaller networks that are not expected to grow significantly.
         • Routing to and from a stub network, which is a network with only one default route out and no knowledge of any remote networks.
         • Accessing a single default route
       • Advantages
         • Easy to implement in a small network
         • Very secure
         • Route to destination is always the same
         • No routing algorithm or update mechaisma required
       • Disadvantages
         • They are not easy to implement in a large network
         • Managing the static configurations can become time consuming
         • If a link fails, a static route cannot reroute traffic
     • Dynamic Routing
       • Uses
         • Dynamic routing protocols help the network administrator manage the time-consuming and exacting process of configuring and maintaining static routes
       • Advantages
         • Suitable in all topologies
         • Generally independent of the network size
         • Automatically adapts topology to remote traffic if possible
       • Disadvantages
         • Can be more complex to implement
         • Less secure
         • Route depends on the current topology
         • Reqiures additional CPU, RAM, and link bandwith

2. RIPv2

   • Configuring the RIP Protocol
     • Advertise Networks
       • Enables RIP on all interfaces that belong to a specific network. Associated interfaces now both send and receive RIP updates
       • Advertises the specified network in RIP routing updates sent to other routers every 30 seconds
     • Very RIP Routing
       • 1. RIP routing is configured and running on router R1
       • 2. The values of various timers; for example, the next routing update, is sent by R1 in 16 seconds
       • 3. The version of RIP configured is currently RIPv1
       • 4. R1 is currently summarizing at the classful network boundary
       • 5. The classful networks are advertised by R1. These are the networks that R1 includes in its RIP updates
       • 6. The RIP neighbors are listed, including their next-hop IP address, the associated AD that R2 uses for updates sent by this neighbor, and when the last update was received from this neighbor
     • Enable and Verigy RIPv2
       • Use the version 2 router configuration mode command to enable RIPv2
       • By default, when a RIP process is configured on a Cisco router, it is running RIPv1
     • Disable Auto Summarization
       • To modify the default RIPv2 behavior of automatic summarization, use the no auto-summary router configuration mode command
     • Configure Passive Interfaces
       • Three ways to sending out unneeded updates on a LAN impacts the network
         • Wasted Bandwidth
         • Wasted Resources
         • Security Risk
     • Propagate a Default Route
       • A default static route using the ip route 0.0.0.0 0.0.0.0 command
       • The default-information originate router configuration command. This instructs R1 to originate default information, by propagating the static default route in RIP updates

3. The Routing Table

   • Parts of an IPv4 Route Entry
     • Directly Connected Entries
       • Route source
       • Destination network
       • Outgoing interface
     • Remote Network Entries
       • Route source
       • Destination network
       • Administrative distance
       • Metric
       • Next hop
       • Route timestamp
       • Outgoing interface