Routed vs. Routing Protocol

• A routing protocol sends and receives routing information packets to and from other routers.
• A routed protocol can be routed by a router, which means that it can be forwarded from one router to another.
• A routed protocol contains the data elements required for a packet to be sent outside of its host netowkr or network segment. In other words, a routed protocol can be routed.
• Protocols used to communicate routing information between routers within an autonomous system are Interior Gateway Protocols (IGP), which are routing protocols, but not routed protocols.

Examples of routed protocols are IP and IPX, and examples of routing protocfols are RIP and IGRP.

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As far as the CCNA exam goes, there are three types of routing: static, dynamic, and default.

Static routes - are fixed routes that are manually entered by the administrator into the router's configuration.

Dynamic routing - is the process by which a network adapts automatically to the changes in topology or traffic as those changes occur.

Default routes - are very much like static route. The administrator enters the default route, and it becomes the default path the router uses to forward packets for which it knows no other route to use. Without a default route, packets with unknown destinations are dripped.

A static route is configured on the router with a command like this:
ip route [destination_network] [mask] [next_hop_address or exit interface] [administrative-distance] [permanent]
Example: RouterA(config)#ip route 192.168.1.0 255.255.255.0 192.168.1.1 3
Using the previous command example the key elements of the static router configuration command are:

ip route: This is the command used to designate a static route.

destination address: in this example, 209.220.93.243 is the IP address of the destination network.

submet mask: 192.169.1.0 is a Class C IP address and is using the default subnet mask for Class C addresses, 255.255.255.0

next hop: Following the subnet mask is the address of the next hop router, 192.168.1.1

administrative distance: This is a number between 0 and 255 that indicates how well the route can be trusted. The higher the number, the lower the trust.

permanent: if the interface is shut down or the router cannot communicate to the next hop router, the route is automatically discarded from the routing table. Choosing the permanent option keeps the entry in the routing table no matter what happens.

Static routing has the following benefits:

No overhead on the router CPU

No bandwidth usage between routers

Security (because the administrator only allows routing to certain networks) Static routing has the following disadvantages:

The administrator must really understand the internetwork and how each router is connected to configure the routes correctly.

If on network is added to the internetwork, the administrator must add a route to it on all routers.

It's not feasible in large networks because it would be a full-time job.

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Routers use a series of calculations and metric-based decisions to determine the most efficient and economical router for a packet to use to reach its destination. In general, these calculations and decisions are embedded in an algorithm.
Here are some of the metrics used to determine the better route:

Bandwidth: Maximum throughput speed in bits-per-second.

Cost: A arbitrary value assigned by the administrator for the crossing and intersection of networks.

Delay (latency): A group of factors such as congestion or distance.

Hop Count: The number of routers a packet passes through to reach its destination.

Load: The measure of traffic that flows through a router.

MTUs (maximum transmission unit): The largest message size allowed on all routes to the destination.

Reliability: A value representing the amount of downtime for a network.

Ticks: A measurement of delay, based on the clock in a personal computer, where one tick is 1/18 of a second. It's used as part of the metric in IPX (Novell) RIP.

For the CCNA exam, you should remember that a distance-vector algorithm is concerned primarily with hop count, or the number of routers that a packet must pass through to reach its destination. RIP and IGRP use distance-vector algorighms. In each of these routing protocols, the routing table lists a remote network and also the number of hops required to get to it.
RIP uses a maximum hop count of 15 and IGRP uses a maximum hop count of 255. Both are distance-vector routing protocols and interior routing protocols.
Three mechanisms used with distance-vector protocols to control routing (count to infinity) loops are split horizon, route poisoning, and hold-downs.

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RIP (Routing Information Protocol) is a classful, distance-vector routing protocol. As such, it uses information provided to it by its neighboring routers to maintain information in a routing table about the cost, in terms of hops and other metrics, of a particular route. For the CCNA exam focus on adding RIP statements to the router.
The IGRP router command requires an autonomous system number to be assigned to the network entries included in the command.
An IPX network address is an 80-bit number that is made up of a 32-bit network ID and the 48-bit MAC address. Because an IPX address includes the MAC address of a node, there's no need for ARP translations on an IPX network.
Novell encapsulations and their Cisco equivalents:

Interface	Cisco Command Word
Ethernet	novell-ehter
Token Ring	sap
FDDI	snap
Serial	hdlc

Novell Frame Types and Their Cisco Equivalents:

Novell	Cisco
Ethernet_802.2	sap
Ethernet_802.3	novell-ether (default)
Ethernet_snap	snap
Ethernet_II	arpa
FDDI_snap	snap (default)
FDDI_raw	novell-fddi
FDDI_802.2	sap
Token-Ring	sap (default)
Token-Rint_snap	snap

Cisco Commands used to Monitor Router Operations:

Command	Action
Privileged Exec Mode	You must be in this mode to use the remaining commands in this table.
ping	Verifies that a network connection is reachable.
show ipx traffic	Displays IPX traffic statistics.
show ipx route	Displays all IPX entries in the routing table or just one entry if the network value is entered.
show ipx interface	Displays a detailed view of an interface's IPX settings.
show ipx servers	Lists the IPX servers discovered through SAP advertisements.
debug ipx sap	Displays messages regarding SAP updates.
debug ipx routing	Displays messages about each routing update.