Mod 14: Routing Concepts

What are the 2 functions of a router?

Determine best path, forward packets to their destination

What is the best path also called?

The longest match

What is the longest match route?

The route with the most far left matching bits with the destination IP of the packet

What are the 3 main ways routers learn routes?

Directly connected, remote networks, default route

What are the 2 ways routers learn about remote networks?

Static, dynamic

What 3 things does a router do after determining best path?

Directly forwards packet, forwards to next hop, drops packet

What is the primary responsibility of router packet forwarding?

To encapsulate packets in the correct L2 frame type

What are the 3 packet forwarding mechanisms supported by routers?

Process switching, fast switching, cisco express forwarding

What are the 5 most common routing table codes?

L, C, S, O, *

What is the prefix length for local IPv4 and IPv6 networks?

/32, /128

What are the benefits of static routes?

More secure, less bandwidth, less CPU usage

What is a stub network?

A network accessed by a single route and the router has a single neighbor

What is a stub router?

A router that only has 1 route to other networks

What are the benefits of dynamic routing protocols?

Can choose best path, can learn new best paths

What is network discovery?

The ability of a routing protocol to share info about known networks to other routers

What are default routes?

Specifies a next hop router when the routing table does not have a best path

What are the 2 types of routes in an IPv4 routing table?

Parent, child

What is AD?

Administrative Distance is a value that determines what route should be added to the routing table

When a router learns about the same route from 2 different sources, what does it use to determine which route to add?

AD value

What are the 2 types of routing protocols?

Interior, exterior

What is the only exterior routing protocol?

BGP

What are the 3 main components of dynamic routing protocols?

Data structures, routing protocol messages, algorithm

How does a routing protocol determine the best path?

A value/metric to determine the distance to reach a network

What does a router do when it has 2 or more routes with the same cost/metrics?

It forwards packets using both paths equally