CCNP CCIE Complete

DHCP is an open standard that is based partly on the BOOTP protocol specified in RFC 951 and RFC 1541. DHCP can be used by Unix, Macintosh, and Windows-based systems. However, the protocol did not attain mainstream corporate recognition until ... [full story]

The commands to configure dynamic addressing depend on the method used. Although DHCP is one option (used as an example in the following text), there are other methods, including proprietary ones. Before we discuss incorporating a dynamic addressing solution, ... [full story]

PPP configuration also requires attention to layer 3 addressing. In this section, IP addressing considerations are presented due to both their complexity and frequency. These include static, IP unnumbered, and dynamic addressing options: Static addressing Clearly, the use of static ... [full story]

To dedicate a line for use by SLIP or PPP, the administrator can use the async mode dedicated command. This command prevents the user from changing the encapsulation protocol and can augment security by restricting the method of access. The ... [full story]

There are a few choices for the administrator or designer to consider when deploying PPP. These choices are above and beyond those that would be used with any other technology such as IP addressing assignments (the actual addresses, not the ... [full story]

Although differences can exist in the configuration methodology needed for different platforms, most steps are consistent and similar. Stated another way, commands for a Cisco access server are different from those for a Shiva LanRover, but the functions are similar. ... [full story]

The Frame Check Sequence field is two octets (16 bits) and provides a cyclical redundancy check (CRC) value, and it is used to validate the packet’s integrity. This is also called a checksum . [full story]

The Information field is also called the Data field . This field contains the data of the packet that has been encapsulated in PPP. The Information field’s length is determined by the amount of user data offered, which can range ... [full story]

Value (in hex) Protocol Name0001 Padding Protocol0021 Internet Protocol0023 OSI Network Layer0025 Xerox NS IDP0027 DECnet Phase IV0029 AppleTalk002b Novell IPX002d Van Jacobson Compressed TCP/IP002f Van Jacobson Uncompressed TCP/IP 0031 Bridging PDU 0035 Banyan VINES 0041 Cisco Systems 0201 ... [full story]

The Protocol field is two octets (16 bits) and identifies the upper layer protocol. An upper layer protocol would include IPCP, the IP Control Protocol. The more commonly assigned Protocol fields and their hexadecimal values are listed in Table 24.1. ... [full story]

The Control field is a single octet (eight bits) and contains the binary sequence 00000011 (0x03 hexadecimal), which is the Unnumbered Information (UI) command. This signifies that the subsequent bits will provide information regarding the remaining data—as opposed to the ... [full story]

The Address field is a single octet (eight bits) with the binary sequence of 11111111 (0xff hexadecimal). This is known as the All-Station Address because PPP does not assign individual station addresses. The field is included to allow addressing; however, ... [full story]

The Flag field is a single octet (eight bits) that indicates the beginning and end of each frame; it has a unique pattern of 01111110. Sometimes, a single flag ends one frame and begins the next. But, as can be ... [full story]

There appear to be two schools of thought on Request for Comments (RFCs) �"the documents that are used to establish and document standards in computer networking. Some believe that only geeks bother to memorize and recite the various RFC numbers, ... [full story]

PPP is documented in RFC 1661 as a standard method for transporting multiple protocols over point-to-point links. PPP substantially improved upon the Serial Line Internet Protocol (SLIP). SLIP transports IP packets only across serial circuits. NOTE:Although beyond the scope ... [full story]

Know the commands and syntax used to configure PPPconnections between the central site and branch offices.
Understand the commands and syntax to configure PAP orCHAP authentication.
Know how to configure multilink services.
Be able to verify and troubleshoot PPP configurations.
Know the commands and ... [full story]

Command Functionline N Cisco routers refer to asynchronous ports as lines. N is equal to the numberof the port and is used before the rest of the commands in this tableto get into line configuration mode.login The login command is ... [full story]

Command Function&F The AT&F command resets most modems to their factory defaults.&C This command configures the modem-for-modem control (C is for CarrierDetect). C1 instructs the modem to use CD to reflect the actual connection status.S0=1 There are a number of ... [full story]

Manual configuration can eliminate the negotiation process required for automatic configuration, but it adds substantially to the configuration process. It requires router configuration changes if the modem is changed, possibly through an upgrade or replacement to a different vendor or ... [full story]

Cisco provides many troubleshooting services to assist in the diagnostic process, and support for troubleshooting the automatic configuration service is no exception. However, before using the debug commands and other troubleshooting tools, it is best to review the status of ... [full story]

To add entries to the modemcap database, the administrator can use the modemcap edit command followed by the database name: modemcap edit modem-profile-name. Configurations provided with the router cannot be modified. Administrators should create a similar user-created entry with their ... [full story]

This section introduces the commands used for automatic configuration. The modem autoconfigure type Command The modem autoconfigure type modem-type command is used to instruct the router to automatically configure the modem attached to a port by using the ... [full story]

Most modern modems provide the capability to identify their type and specifications, which a computer or router can use to assist in the configuration process. Obviously, the benefit of automatic configuration is that it reduces the number of administrative tasks ... [full story]

Asynchronous connections, like other connections, require configuration before they can be used. In applications using Cisco routers, this configuration can be supplemented with automatic functions or it can be manual. As such, there are three possible configuration options:  Manual ... [full story]

Error correction validates the integrity of the data and is frequently used with compression to verify that the compression process did not corrupt the data. The impact of a single-bit error can distort substantial amounts of compressed data—instead of just ... [full story]

Data compression substitutes repetitive data in a bit stream with fewer bits that will be interpreted, or uncompressed, on the other device. Later in this book, we will present a more detailed example of data compression; for this introduction, it ... [full story]

Modulation Standards Modulation defines the method used to encode the data stream between DCE devices. There are many modulation standards, including several proprietary methods. Modems will negotiate the modulation standard to be used during the connection. Modern modems will ... [full story]

DTE-to-DCE Signaling Wire Function TXD Transmits data from the DTE to the DCE. All serial connections send their data one bit at a time over a single transmission path. This differs from parallel transmissions that have multiple paths. Printers, ... [full story]

The cables used in various asynchronous connections differ depending on the end equipment plus the type and distance of the connection. Modems typically use two types of connectors—one for the connection to the host and one for the connection to ... [full story]

When discussing the limitations of serial signaling, it would be remiss not to discuss the limitations of the public phone system and the analog technology available today. As noted earlier in this chapter, asynchronous connections are limited to 56Kbps, or ... [full story]

Understanding Asynchronous Modems Technically, modems are modulator/demodulators, but most people define them by their highlevel function: modems connect devices to the telephone network. The modem connects the computer or router to the phone network and might incorporate a pass-through for ... [full story]

AsynchronousConnections
Know the commands and procedures necessary to configure an access server for modem connectivity so telecommuters can access the central site.
Know the commands and procedures to configure dial-out connections.
Know the commands used for ... [full story]