Introduction to Routing

The purpose of Data Link Layer (Layer 2) is to deliver frames across

• the internet

• a single link

• several networks

• a adjacent networks

The job of the Network Layer is to deliver packets across

• the internet

• a single link

• networks along the best path

• a single network

Select all of the frame formats on the wide area network (WAN) side

• ATM

• Frame Relay

• PPP

• Ethernet

Select all that applies to a router

• Each side of a router is a different network with its own identity

• Each side of a router is on the same broadcast domain

• Routers connect end-devices to end-devices

• Routers do encapsulation / decapsulation of packets into and out of frames

A routing table contains (select all that is correct)

• A list of all networks known to the router

• The cost to reach each network

• The direction that packets can be sent to reach the network

• The MAC addresses of end-devices

Routers use a priority system to make decisions as to how to send packets across multiple redundant paths, what is the first step in this priority system ?

• If there are multiple entries in the routing table for the same network which is of the same size and has the same cost, choose one entry at random and deliver the packet using the Via information on that route.

• If multiple routes have the same size, then choose the route with the lowest cost.

• If multiple routes match the destination IP address, choose the route that has the smallest IP address range

• The destination IP address must fall in the network range of a route entry.

How do routers establish route entries (select all that is correct) to build the route table ?

• Router learn about networks that are directly connected to them.

• Route entries can be manually entered by network administrators

• Routers learn about networks using the DHCP server.

• Network administrators can setup a dynamic routing protocol on routers

If an entry in the routing table is out of date or points in the wrong direction, then (select all that applies)

• packets may take a path to the destination network which is not the best path

• packets may loop around and around within the network and eventually get delivered.

• packets may never reach the network because a router drops them when it does not have a route to that network

• packets may loop around and around within the network and never get delivered.

What do you understand by the term convergence in relation to routers?

• the state where all routers have accurate and up to date knowledge of all the users in the wider network

• the state where all routers have accurate and up to date knowledge of all the end devices in the wider network

• the state where all routers have accurate and up to date knowledge of all the switches in the wider network

• the state where all routers have accurate and up to date knowledge of all the networks in the wider network

What are the goals of a dynamic routing protocol (select all that is correct) ?

• To find and use an alternate route if an existing route is removed from the table.

• To dynamically learn and fill the routing table with a route to all networks in the overall internet.

• If more than one route to a network is available, to put the best route in the routing table. The other routes may also be added as fallback entries.

• To determine when routes in the table are no longer valid, and to remove them from the routing table.