Dynamic Routing Protocols

Question 1

Dynamic routing protocols

Answer 1

• Listen for subnet information from other routers
  
  • Sent from router to router
• Provide subnet information to other routers
  
  • Tell other routers what you know

• Determine the best path based on the gathered
information
• Every routing protocol has its own way of doing this

• When network changes occur, update the available
routes
• Different convergence process for every dynamic
routing protocol

Question 2

Which routing protocol to use?

Answer 2

• What exactly is a route?
  
  • Is it based on the state of the link?
  • Is it based on how far away it is?

• How does the protocol determine the best path?
• Some formula is applied to the criteria to create a
metric
• Rank the routes from best to worst

• Recover after a change to the network
• Convergence time can vary widely between routing
protocols

• Standard or proprietary protocol?
• OSPF and RIP are standards, some functions of
EIGRP are Cisco proprietary

Question 3

Distance-vector routing protocols

Answer 3

• Information passed between routers contains routing
tables
• How many “hops” away is another network?
• The deciding “vector” is the “distance”

• Usually automatic
  
  • Very little configuration
• Good for smaller networks
  
  • Doesn’t scale well to very large networks
  • RIP, RIPv2, EIGRP

Question 4

Link-state routing protocols

Answer 4

• Information passed between routers is related to the
current connectivity
• If it’s up, you can get there.
• If it’s down, you can’t.

• Consider the speed of the link
  
  • Faster is always better, right?
• Very scalable
  
  • Used most often in large networks
  • OSPF - Large, scalable routing protocol

Question 5

Hybrid routing protocols

Answer 5

• A little link-state, a little distance-vector
  
  • Not many examples of a hybrid routing protocol

• BGP (Border Gateway Protocol)
• Determines route based on paths, network policies,
or configured rule-sets