Routing

Static Routing
Manually added routes


Dynamic Routing
Self-learned routes. E.g. RIP (Routing Information Protocol), OSPF , EIGRP ETC.

Administrative Distances
Trustworthiness of a routing information

The lower the value, the higher the trustworthiness
The higher the value, the lower the trustworthiness

What is an administrative distance of 0?

0 is the default administrative distance for directly connected routes. The router trusts a 0 distance the MOST.

What is the administrative distance used for in static routes?

To rate the source’s trustworthiness. Same as dynamic, it assigns the weighted averages of the links, 255 is the last resort, least trusted.

Static routes are used for which of the following?

Defining a path to an IP destination network. Building routing tables to remote networks.

What is the command that you should use when using static and default routes with your Cisco routers?

The ip classless command tells the router to expect subnetted internetworks on its interfaces. Default is classful mode, which means they look for an entire address class on each interface and do not consider the subnets when making routing decisions.

What is the command syntax to set a gateway of last resort in your Cisco router?

“ip route 0.0.0.0 0.0.0.0 Next hop address” sets a gateway of last resort, or default.

Which Cisco IOS command can you use to see the routing table?

“sh ip route” shows the IP protocol routing table maintained in the router. Sh ipx route will show IPX.

What are three ways that routers learn paths to destinations?

Static, default or dynamic routing.

When should you use static routing instead of dynamic routing?

When you have very few routers and want to save bandwidth. Dynamic routing takes up a great deal of bandwidth. On a slow WAN link static routes may be a better solution.

What are three ways to build routing tables?

Router learns routes by default, statically, or dynamically.

What is the command syntax for creating an IP static route in a Cisco Router?

IP route destination_network subnet_mask default_gateway

How do you create a default route?

By using all zeros to specify the remote network and the subnet mask. The router will use this route as the gateway of last resort.

When looking at a routing table, what does the “S” mean?

Statically connected

What is true about IP routing?

A device will send a frame with the hardware destination or the default gateway. The router will strip the frame and put the datagram in a new frame with the new remote destination address.

What static route parameter will tell a router the name of the interface to use to get to a destination network?

INTERFACE , “ip route INTERFACE ”

The interface parameter is rarely used, but can be used to tell a router what interface to use for a route to a remote network.

When creating a static route, what is the gateway parameter used for?

Defining the next hop.

What does a router do with a received packet that is destined for an unknown network?

It will drop the packet and send an ICMP reply to the sending host.

What is true when creating static routes?

Gateway is required, the administrative distance is optional.

“ip route INTERFACE ”

Interface not required.

When looking at a routing table, what does the “C” mean?

Directly Connected