Dynamic Routing Protocols

Role of Dynamic Routing Protocol

Dynamically learn information about remote networks and add routes to routing tables.

Determines the best path to each network.

Automatically finds alternate paths if needed.

Advantages of Dynamic Routes over Static Routes

Less administrative overhead.

Scales better.

Less prone to configuration errors.

3 components of Dynamic Routing protocols

1. Data Structures

2. Algorithms

3. Routing Protocol Messages

Define: Routing Protocol Messages

Messages to discover neighboring routers

Exchanges, learns, and maintains accurate network routing information

Define: Distance Vector

Routing protocol that determines the best route for data packets based on distance and direction.

Define: Distance and Direction (in a distance Vector)

Distance - The Hop Count

Direction - The next-hop router / exit interface

What does Routing updates for Distance Vectors usually consist of?

Periodic updates (30sec for RIP) of the entire routing table.

Benefits of Distance Vectors

1. Better for networks with fewer routers and a straightforward network

2. Requires less knowledge with configs and troubleshooting

3. Convergence Time not a concern

Define: Link State

A dynamic routing algorithm that calculates the optimal path for transmitting data by having the devices create a complete map of the network topology.

What does a link-state router do in the topology?

-Receives an update.

-Builds a topology database.

-Uses a Shortest Path First (SPF) algorithm to create its view of the network.

-Builds the routing table.

When are routing updates sent in a Link-state network?

Only when the topology changes. But doesn’t update the entire table.

Pros and Cons of Link States:

Pros:

1. Hierarchical designed better for larger networks

2. Fast Convergence

Cons:

1. Requires more knowledge

Definition: Convergence

When all routers have complete and accurate information about the network

When a router has multiple paths to the same destination, what’s used to compare routes to determine the best ones?

Metrics

Which Routing Protocols are slower/faster?

Slower:

• RIP

Faster:

• EIGRP

• OSPF

What metrics does RIP use?

Hop count, lower the better.

What metrics does OSPF use?

Bandwidth, faster the better

The routing table displays the ______ for both dynamic and static route

metrics

What does the routing table show for static route metrics?

0

Define: Load balancing

What happens if 2+ routes to the same destination have the same metrics?

Load balance

Define: Administrative Distance (AD)

Determines which route is to be installed in the routing table

The lower the administrative distance value, the more _________ the route

Trustworthy

What are the Administrative Distances for all the route sources?

Connected 0

Static 1

EIGRP summary route 5

External BGP 20

Internal EIGRP 90

OSPF 110

RIP 120

External EIGRP 170

Internal BGP 200