ICND1 - 5. Routing

Provide a brief description of routing.

Routing is the process of finding a path to a destination and moving information across an internetwork from the source to the destination.

What is the difference between a routed and a routing protocol?

A routed protocol is a protocol that provides the information in its network layer to allow a packet to direct traffic and defines the use of fields within a packet. Examples of routed protocols are IPv4 and IPv6. A routing protocol finds routes in an internetwork and maintains route awareness. Routing protocols aid in building and maintaining routing tables that routers will use to determine how routed protocols are routed. Routing Information Protocol v2 (RIPv2), Enhanced IGRP (EIGRP), Intermediate System-to-Intermediate System (IS-IS), Open Shortest Path First (OSPF), and Border Gateway Protocol (BGP) are examples of routing protocols.

How does a router determine the path a packet should take to reach its destination?

A router determines a path a packet should take to reach a destination by picking the best path to the destination. The best path a packet should take is determined by one of the following methods: Static routing Dynamic routing Default routing

What is the Address Resolution Protocol (ARP)?

ARP is used to resolve a known destination IP address to its associated MAC address on the local network. For a host to communicate with another host, it must know the MAC address of the destination host. If the hosts are on the same subnet, the sending host will send an ARP request to the destination asking for its MAC address. The destination host will reply with its MAC address. If the sending host and the destination host are on a different subnets, the ARP request is sent to default gateway. The default gateway will reply to the ARP request with its MAC address on the local subnet of the sending host and the logical address of the destination host. Note ARP takes the destination IP address and resolves it to the MAC address on the local network through a local broadcast. For the exam, remember that ARP is used when a device knows the destination IP of another device and needs to learn the destination MAC address of that device on the local network.

What is a default route?

Also known as the gateway of last resort, a default route is a special type of route with an all-0s network and network mask. The default route directs any packets for which a destination network is not specifically listed in the routing table. By default, if a router receives a packet to a destination network that is not in its routing table, it drops the packet. When a default route is specified, the router does not drop the packet. Instead, it forwards the packet to the IP address specified in the default route.

What is an example of a Layer 2 address?

An example is a MAC address. Ethernet interface manufacturers assign MAC addresses to end devices and are used for communication over the local network. MAC addresses are hard-coded into the network card and Ethernet interfaces.

What are dynamic routes?

Dynamic routes use a routing protocol to dynamically learn routes to remote networks and add them to the routing table. The routing protocol automatically updates route knowledge whenever new topology information is received.

How do routing protocols maintain their routing tables with each other?

Routing protocols maintain their routing tables through the transmission of messages. These messages are exchanged between routers at periodic intervals or when a change in the network topology occurs. The information contained in the messages varies from routing protocol to routing protocol.

What are static routes?

Static routes are routes to a remote destination that are manually configured on a router. They are administrator-defined routes and allow precise control over routing behavior.

What is the ARP table?

The ARP table stores the reference of each known IP address to its MAC address on the local Layer 3 network. The ARP table is created and maintained dynamically but can also include static ARP entries.

What are six types of information stored in routing tables?

The following are six types of information stored in routing tables: Destination network address Next-hop address Exiting interface Metric Administrative distance Routing source

What are the four types of routes found in a routing table?

The four types of routes found in a routing table are as follows: Directly connected networks: Route entries that a router is directly connected to. Static routes: Routes entered manually by an administrator. Dynamic routes: Routes learned and populated by a routing protocol. Default route: Used to route packets when the router does not have a specific destination for packets in its routing table. The default route is entered manually or dynamically.

What three configuration settings does a host on a TCP/IP network require to communicate with hosts on a remote TCP/IP network?

The three configuration settings needed to communicate with hosts on a remote TCP/IP network are IP address Subnet mask Default gateway address

What are the two key functions that a router performs?

The two key functions that a router performs are path determination (routing) and packet forwarding (switching). Routing protocols used by the routing process are responsible for learning and maintaining awareness of the network topology. The switching function is the process of moving packets from an inbound interface to an outbound interface.

List three advantages and disadvantages of static routes when compared with dynamic routing.

Three advantages of static routing are They conserve routing resources that are consumed when using a routing protocol. Simple to configure in a small network. Quick to implement. Three disadvantages are Scalability is limited. Static routes should be used for small networks or stub networks. A lot of manual configuration is required for larger networks. Do not automatically adapt to network changes.

What two utilities test IP connectivity?

Two utilities are ping and traceroute (tracert). Ping and traceroute are ICMP utilities. ICMP specifically tests Layer 3 connectivity. Traceroute uses UDP when sending packets and ICMP when responding to the request of connectivity.

You want to test TCP/IP connectivity between two hosts. What TCP/IP tools can you use to do this?

You can use ping and traceroute. Ping is a tool that that sends Internet Control Message Protocol (ICMP) packets to test network layer connectivity between two hosts. Ping sends an ICMP echo request packet to the target host and listens for an ICMP echo response. Traceroute also uses ICMP, and it maps the path packets use to reach a destination.