Dynamic Routing Protocols Flashcards
What does a routing protocol do?
Allows routers to share best paths to known networks with each other.
How do routers utilize routing protocols?
Routers take the information of best known paths from other routers to determine their own best path. This includes when routing paths go down or when network states change. These changes are done automatically.
What are the two types of routing protocols
Internal Gateway Protocols (IGPs) and External Gateway Protocols (EGPs)
What are interior gateway protocols (IGPs) used for?
Exchanging routing information between routers within an organization.
What are exterior gateway protocols (EGPs) used for?
Exchanging routing information over the Internet between organizations.
What are the types of EGPs used today?
Path Vector Routing Protocol.
What are the types of IGPs used today?
Distance Vector routing protocols and Link state routing protocols.
How do Distance Vector routing protocols work?
Routers only know what’s connected to them and their neighbors.
How do Link State routing protocols work?
Routers shares its connections to its neighbors and that information is passed to every other router in the network.
What are examples of Distance Vector routing protocols?
Routing Information Protocol (RIP) and Enhanced Interior Gateway Routing Protocol (EIGRP)
What are examples of Link State routing protocols?
Open Shortest Path First (OSPF) and Intermediate System - Intermediate System (IS-IS)
What is an example of a Path Vector Routing Protocol
Border Gateway Protocol (BGP). This is the only EGP used today.
How do IGPs know which path to put into a router’s routing table?
Each IGP use a different method to calculate a metric value. The lower the metric value, the better the path. This determines which path is the best path.
How do Distance Vector metrics work?
Each router advertises its known network and shares their metric to get to each of them.
How do Link State metrics work?
Each router takes the information of all the other routers and network information and calculates its own best path.
How do Routing Information Protocol (RIP) Metrics work?
They use hop count, meaning how many routers they go through to get to a destination. Cannot really manipulate the metrics.
How do Open Shortest Path First (OSPF) Metrics work?
It uses a “cost” method, where it takes into account bandwidth by default.
How do IS-IS Metrics work?
Also uses a “cost” method, but does not take into account bandwidth. If costs are not manually set, it takes the lowest hop count.
How do EIGRP Metrics work?
Uses a calculated number determined primarily by bandwidth. Can manually configure path if needed.
What happens when multiple paths have the same cost in IGPs?
All IGPs use Equal Cost Multi Path (ECMP) by adding all paths into the routing table and load balancing the information between them.
What is the purpose of Administrative Distance
Administrative distance is used to determine the priority and best path when routers use multiple routing protocols.
How does administrative distance work?
Priority values are assigned to different routing protocols to determine which protocol to use and then it uses metrics to determine which path to take.
What is the purpose of floating static routes
Because static routes have a value of 1, administrative distance will always take the static path route. Floating static routes allows us to assign static routes as a backup route in case the original best path fails. This is done by assigning a AD value just above the priority value of the routing protocol.
What is a loopback interface?
Virtual interface that’s always up as long as there’s one IP interface that works
If a path is down, how does a loopback interface solve this issue?
A loopback interface allows a single address across multiple interfaces so that when on path goes down, traffic can be rerouted to another interface.
What is the purpose of a passive interface
Passive interfaces allows you to know about the link, while not sending routing information to the device on the other side. Think of it like one way streets.
Why should you always configure a loopback interface as a passive interface.
This way it will advertise its information, but not waste resources sending out and listening for hello packets. Loopbacks will never have adjacencies.
