Distance Vector
Examining the Cisco IP Routing Table
Routing tables are generated by devices learning new remote networks using some form of a routing protocol. Routing tables are used by routers, for example, to make intelligent decisions regarding where packets should be sent so that user data is sent as efficiently as possible. Hence, one of the most common IOS commands used on a Cisco router is to display a routing table. The command to display the IP routing table on a Cisco router is This command can also be written as The Internet routing...
Internetwork Packet Exchange IPX
The addressing method used in IPX is a network with the source MAC address appended 32 bits is used to identify the IPX network and 48 bits identifies the host portion, because the burned-in address (BIA) is used to identify the node or client address to IPX. IPX allows clients and servers to communicate locally or remotely. The routing protocol can be IPX RIP or Cisco propriety EIGRP on Cisco routers. Figure 2.8 shows the relationship between the OSI model and...
OSI Model Layers
The following sections provide descriptions and typical examples of each OSI layer. Furthermore, examples of communication methods and functions follow each layer description. The Physical layer consists of standards that describe bit ordering, bit transmission rates, connector types, and electrical specifications. Information is transmitted as binary bits (ones and zeros). Examples of Physical layer standards include the following The Data Link layer will focus on getting data reliably across...
How Data Flows through the OSI Layers
To get a better understanding of how the OSI layers function, it is important to know how data flows between the layers. In this section, we'll trace the data as it flows through the layers of the OSI model. As you will see in this section, each layer adds (or encapsulates) some form of header or trailer. (Layer 2, the Data Link layer, is responsible for adding a trailer.) Figure 2.2 shows the data flow from Device A to Device B. Note The example in Figure 2.2 demonstrates how end user packets...
Common Routing Characteristics
Routing protocols use certain features to ensure that valid routing information is gathered as accurately as possible and without corruption. This section discusses IP RIP as an example. IP RIP is widely used in the Unix industry and is relatively easy to configure and maintain. To enable RIP on a Cisco router, you simply type the command router rip and then enable the networks you wish to be advertised with the network < address> command. Note Chapter 6provides a detailed example of IP RIP...
Maximum Transmission Unit MTU
MTU specifies the maximum frame size allowed across a medium. For example, on an Ethernet interface on a Cisco router, the default MTU size is set to 1,500 bytes. X.25 can go as low as 128 bytes. Listing 2.4 displays the Ethernet statistics taken from a Cisco router's Ethernet interface, note the MTU size is readily visible. Listing 2.4 Show interface Ethernet0 command output. R1 sh interface ethernet0 Ethernet0 is up, line protocol is up Hardware is Lance, address is 0060.7015.5e4d (bia...
Routing Vs Routed Protocols
Routing protocols apply a set of rules to a network topology to determine the best path to a destination from a given reference point. They also communicate network topology information to other routers in their networks. Routing protocols build routing tables from the gathered information. Examples of routing proto cols are Open Short Path First (OSPF) and IPX's Routing Information Protocol (IPX RIP). In contrast, a routed protocol is a protocol that contains layer 3 information that allows it...
Transmission Control Protocol TCP
The Transmission Control Protocol (TCP) address transports functions of the OSI model. The Transport layer is primarily concerned with end-to-end data transport to the upper layers of the OSI model. TCP delivery is guaranteed. TCP also provides error checking. TCP runs over the IP protocol and is a connection-orientated protocol. It also uses windowing and acknowledgments to ensure segments are sent as efficiently as possible. Unlike IP, TCP will reorder segments that arrive at the destination....
IEEE 802x Protocols
The IEEE has defined various standards that relate to the 802.x protocols family, such as the descriptions for Ethernet in 80.2.3. Table 2.4 shows the IEEE standards for 802.x protocol standards, where x represents a standard. Memorize the most common 802.x protocol standards, such as Ethernet 802.3. You need to be able to identify which protocol standard is relevant to Ethernet or Token Ring in today's networks. Each IEEE standard has limitations, such as cable length and transmission speed....