Blog2Blog Maak je eigen Blog2Blog | Gratis je eigen blog c.q weblog op internet
CCNA Geheugensteuntje

CCNA Geheugensteuntje

Home - Profile - Archives

EIGRP - Posted at 14:57 on 20/1/2007 by @lfons

Underlying Processes and Technologies

To provide superior routing performance, Enhanced IGRP employs four key technologies that combine to differentiate it from other routing technologies: neighbor discovery/recovery, reliable transport protocol (RTP), DUAL finite-state machine, and protocol-dependent modules.

The neighbor discovery/recovery mechanism enables routers to dynamically learn about other routers on their directly attached networks. Routers also must discover when their neighbors become unreachable or inoperative. This process is achieved with low overhead by periodically sending small hello packets. As long as a router receives hello packets from a neighboring router, it assumes that the neighbor is functioning, and the two can exchange routing information.

Reliable Transport Protocol (RTP) is responsible for guaranteed, ordered delivery of Enhanced IGRP packets to all neighbors. It supports intermixed transmission of multicast or unicast packets. For efficiency, only certain Enhanced IGRP packets are transmitted reliably. On a multiaccess network that has multicast capabilities, such as Ethernet, it is not necessary to send hello packets reliably to all neighbors individually. For that reason, Enhanced IGRP sends a single multicast hello packet containing an indicator that informs the receivers that the packet need not be acknowledged. Other types of packets, such as updates, indicate in the packet that acknowledgment is required. RTP contains a provision for sending multicast packets quickly when unacknowledged packets are pending, which helps ensure that convergence time remains low in the presence of varying speed links.

The DUAL finite-state machine embodies the decision process for all route computations by tracking all routes advertised by all neighbors. DUAL uses distance information to select efficient, loop-free paths and selects routes for insertion in a routing table based on feasible successors. A feasible successor is a neighboring router used for packet forwarding that is a least-cost path to a destination that is guaranteed not to be part of a routing loop. When a neighbor changes a metric, or when a topology change occurs, DUAL tests for feasible successors. If one is found, DUAL uses it to avoid recomputing the route unnecessarily. When no feasible successors exist but neighbors still advertise the destination, a recomputation (also known as a diffusing computation) must occur to determine a new successor. Although recomputation is not processor-intensive, it does affect convergence time, so it is advantageous to avoid unnecessary recomputations.

Protocol-dependent modules are responsible for network layer protocol-specific requirements. The IP-Enhanced IGRP module, for example, is responsible for sending and receiving Enhanced IGRP packets that are encapsulated in IP. Likewise, IP-Enhanced IGRP is also responsible for parsing Enhanced IGRP packets and informing DUAL of the new information that has been received. IP-Enhanced IGRP asks DUAL to make routing decisions, the results of which are stored in the IP routing table. IP-Enhanced IGRP is responsible for redistributing routes learned by other IP routing protocols.

EIGRP - Posted at 14:57 on 20/1/2007 by @lfons

Enhanced IGRP

The Enhanced Interior Gateway Routing Protocol (EIGRP) represents an evolution from its predecessor IGRP (refer to Chapter 42, "Interior Gateway Routing Protocol"). This evolution resulted from changes in networking and the demands of diverse, large-scale internetworks. Enhanced IGRP integrates the capabilities of link-state protocols into distance vector protocols. Additionally, EIGRP contains several important protocols that greatly increase its operational efficiency relative to other routing protocols. One of these protocols is the Diffusing update algorithm (DUAL) developed at SRI International by Dr. J.J. Garcia-Luna-Aceves. DUAL enables EIGRP routers to determine whether a path advertised by a neighbor is looped or loop-free, and allows a router running EIGRP to find alternate paths without waiting on updates from other routers.

Enhanced IGRP provides compatibility and seamless interoperation with IGRP routers. An automatic-redistribution mechanism allows IGRP routes to be imported into Enhanced IGRP, and vice versa, so it is possible to add Enhanced IGRP gradually into an existing IGRP network. Because the metrics for both protocols are directly translatable, they are as easily comparable as if they were routes that originated in their own autonomous systems (ASs). In addition, Enhanced IGRP treats IGRP routes as external routes and provides a way for the network administrator to customize them.

This chapter provides an overview of the basic operations and protocol characteristics of Enhanced IGRP.

Enhanced IGRP Capabilities and Attributes

Key capabilities that distinguish Enhanced IGRP from other routing protocols include fast convergence, support for variable-length subnet mask, support for partial updates, and support for multiple network layer protocols.

A router running Enhanced IGRP stores all its neighbors' routing tables so that it can quickly adapt to alternate routes. If no appropriate route exists, Enhanced IGRP queries its neighbors to discover an alternate route. These queries propagate until an alternate route is found.

Its support for variable-length subnet masks permits routes to be automatically summarized on a network number boundary. In addition, Enhanced IGRP can be configured to summarize on any bit boundary at any interface.

Enhanced IGRP does not make periodic updates. Instead, it sends partial updates only when the metric for a route changes. Propagation of partial updates is automatically bounded so that only those routers that need the information are updated. As a result of these two capabilities, Enhanced IGRP consumes significantly less bandwidth than IGRP.

Enhanced IGRP includes support for AppleTalk, IP, and Novell NetWare. The AppleTalk implementation redistributes routes learned from the Routing Table Maintenance Protocol (RTMP). The IP implementation redistributes routes learned from OSPF, Routing Information Protocol (RIP), Intermediate System-to-Intermediate System (IS-IS), Exterior Gateway Protocol (EGP), or Border Gateway Protocol (BGP). The Novell implementation redistributes routes learned from Novell RIP or Service Advertisement Protocol (SAP).

Alles in een - Posted at 14:31 on 20/1/2007 by @lfons

1. Networking fundamentals






TCP/IP Protocols






Application (7)




o.a.:HTTP, SMTP,

Presentation (6)





Session (5)





Transport (4)





Network (3)





Datalink (2)


Network Access


o.a. Ethernet, Frame

Physical (1)




Relay, PPP



Application Layer (7)

This layer is responsible for file, message, print, database, and application services. It is also responsible for synchronizing applications on the client and the server, determining if sufficient resources exist for the intended communication, understanding resources that are needed to communicate between two devices and establishing their availability, agreeing on error control and data integrity of communicating applications, and providing processes and services to end users. Always think of “data” with this layer.


Presentation Layer (6)

Responsible for the format, conversion, encryption, decryption, compression, and decompression of data. This layer also negotiates which format or syntax to use, such as PICT, TIFF, JPEG, MIDI, QuickTime, and MPEG. This layer presents data to the Application layer, so basically, it services the Application layer and is serviced by the Session layer. Always think of “data” with this layer.


Session Layer (5)

This layer is responsible for establishing, managing, and terminating sessions between applications. Its main concern is dialog control between nodes, or devices. It keeps data from different applications separate from each other and offers three modes: simplex, half-duplex, and full-duplex. Some examples of Session Layer protocols and interfaces are SQL (Structured Query Language), RPC (Remote Procedure Call), X Window, and Network File System (NFS). Always think of “data” with this layer.


Transport Layer (4)            [TCP, UDP, SPX]

Responsible for sequencing, session establishment, and maintenance and termination (tear-down) of virtual circuits. Services in this layer segment and reassemble data from upper-layer applications. It establishes a logical connection between the sending host and the destination host. Always think of “segments” with this layer.


Network Layer (3)              [IP, IPX]

This layer decides the best path through a network and handles network addressing. It is responsible for routing within an internetwork. Routers are defined at this layer.  Always think of “packets or datagrams” with this layer.


Data Link Layer (2)             [802.3/802.2, HDLC]

Responsible for providing reliable transmission of data across the Physical layer. It formats the message into data frames and adds a header to the frame containing the hardware source and destination address. Consists of two sublayers: Media Access Control (MAC) and Logical Link Control (LLC). The MAC sublayer is responsible for Media Access, Framing, and Logical Topology. The LLC sublayer can provide error correction while the MAC sublayer only provides error detection. Always think of “frames” with the Data Link layer


Physical Layer (1)              [EIA/TIA-232, V.35]

This layer is responsible for sending and receiving bits. It specifies the electrical, mechanical, functional, and procedural requirements for activating, maintaining, and deactivating a physical link between systems. It is where the cable, connector, and signaling specifications are defined. This layer is the only layer that does not rely on a layer beneath it and the only one that can communicate electrical/light pulses to the other side. Always think of “bits” with this layer.

2. Operating Cisco Devices


Cisco Router Memory Types:

RAM                        Working Memory and Running-Configuration

Flash                       Cisco IOS Software (IOS= Internetwork Operating System)

ROM                        Basic Cisco IOS Software

NVRAM                   Startup-Configuration (NVRAM= NonVolatile RAM)


Image naming conventions: you can identify  Platform, Features, Image location and compression status



Editing Commands:

Ctrl + A                                   Move to the beginning of the command line

Ctrl + E                                   Move to the end of the command line

Ctrl + B (or left arrow)               Move back one character

Ctrl + F (or right arrow)             Move forward one character

Ctrl + N (or down arrow)            Repeat most recent command

Ctrl + P (or up arrow)                Repeat previous command

Ctrl + D                                   Deletes a single character

Ctrl + R                                   Redisplays a line

Ctrl + U                                   Erases a line

Ctrl + W                                  Erases a word

Ctrl + Z                                   Ends configuration mode and returns you to exec mode


Esc + B                                  Move backward one word

Esc + F                                  Move forward one word


Backspace                              Deletes a single character

Tab                                         Finishes typing a command (not on exam?)


Shift+Ctrl+6 then x                   To suspend Telnet-session. (show sessions, resume nbr, disconnect nbr)




EXEC includes the following:

Context-sensitive help for syntax checking, command prompting, and keyword completion. Use the question mark (?) to activate context-sensitive help. (not on the exam)


>  user mode        # privileged mode                               Setupmode : is triggered on startup when NVRAM is empty     


Enhanced editing that enables commands retrieved from command history to be changed quickly then re-executed. The terminal editing and terminal no editing commands enable and disable enhanced editing.


Examine the status of a router with the following commands: show version, show memory, show protocols, show running-config (or write terminal), show startup-config (or show configuration), show interfaces, show flash and

show ip protocol


The Cisco Discovery Protocol (CDP) displays summary information about directly connected devices and operates at the data link layer.

The show cdp neighbors [detail]command displays ID, local and remote port, holdtime, platform, and capability information.

The show cdp entry  command displays information about a specific device including all layer 3 addresses and Internetwork Operating System (IOS) versions. (device id is case sensitive)

Switch CDP on or off: Entire router:  (config)cdp run  Interface: (config-if)cdp enable



The command to back up a router configuration file (copy a configuration file from a router to a Trivial File Transfer Protocol [TFTP] server) is copy running-config tftp.

The command to restore a configuration file (copy a configuration file from a TFTP server to a router) is:

copy tftp running-config.



Configure and show host-table:

Router(config)#ip host

Router#show hosts









Password from user execute mode to privileged execute mode


Router(config)#enable password password   




VTP - Posted at 14:30 on 20/1/2007 by @lfons


Create, modify en delete VLANs,

Send/forward VTP advertisements

Synchronizes VLAN

VLAN are save in NVRAM


Synchronizes VLAN

Send/forward VTP advertisements


Create, modify en delete VLANs

forward VTP advertisements

VLAN are save in NVRAM

RIP / IGRP / IPX - Posted at 14:29 on 20/1/2007 by @lfons






Default routing matrix

Nr hops


( Load, Reliability, MTU)

Nr Hops



Administrate distance





Update Timers




Na hoeveel seconden wordt de tabel geupdated

Invalid timers


3x Update time


Hoe lang moet een router wachten voordat een route "invaled" is

Holddown timers


3x Update time + 10


Hold down periode

Flush timers


7x Update time


De tijd voordat een route van de tabel wordt verwijderd.

Max hops




Loops - Posted at 14:29 on 20/1/2007 by @lfons

Max hop Counts

Maximaal Aantal hops

Slip Horizon

Informatie kan niet worden terug verzonden in de richting van waar hij kwam

Routing Poisoning

Markeert de route als niet te gebruiken


Timer, voorkomen van "knipperen"

IGP / EGP - Posted at 14:28 on 20/1/2007 by @lfons


Interior Gateway Protocol

Within an autonomous system


Exterior Gateway Protocol

Between autonomous systems

Link State / Balanced Hybrid - Posted at 14:22 on 20/1/2007 by @lfons

Distance vector

Determines the direction, bepaald de richting

Zend tabel naar zijn buren


Recreates the exact topology

Gebruikt Link State Packets

Balanced hybrid



netwerkadressen - Posted at 14:20 on 20/1/2007 by @lfons

Network address 0

Dit netwerk of segment

Network address 1

Alle netwerken

Network address

Gereserveerd voor loopback test

Node address 0

Deze node

Node address 1

Alle nodes

Alles 0

Gebruikt door Cisco routers om de default route aan te wijzen

Alles 1

Broadcast naar alle nodes




Private: - - - -


IP - Posted at 14:19 on 20/1/2007 by @lfons


8 bits

8 bits

8 bits

8 bits

Fist Bit

Class A





0 -> 0-127


Class B





10 -> 128-191


Class C





110 -> 192-223


Class D


Tussen 224-255 gereserveerd


Class E



ICMP / ARP / R-ARP - Posted at 14:19 on 20/1/2007 by @lfons


  • Internet Control Message Protocol
  • Werkt op de netwerklaag
  • Gebruikt IP voor verschillende services
  • Destination Unreachable
  • Buffer Full
  • HOPS
  • Traceroute
  • Ping


  • Address Resolution Protocol
  • Wordt gebruikt om de hardware address (MAC) te achterhalen van een host met een IP address


  • Reserve Address Resolution protocol
  • Zorgt ervoor dat een "disc less machine" een IP address krijgt.
UDP Frame - Posted at 14:18 on 20/1/2007 by @lfons

Source port (16)

Destination port (16)

Length (16)

Checksum (16)

Data (varies)

TCP Frame - Posted at 14:18 on 20/1/2007 by @lfons

Source port (16)

Destination port (16)

Sequence number (32)

Acknowledgment (32)

Header Length(4)

Reserved (6)

Code bits (6)

Window (16)

Checksum (16)

Urgent Pointer(16)

Options (0-32)

Data (varies)

TCP/IP Protocol - Posted at 14:17 on 20/1/2007 by @lfons

Application layer








Transport Layer (h-h)



Internet Layer


Network Access


Fast Ethernet

Token ring


Switch Types - Posted at 14:17 on 20/1/2007 by @lfons

Type Switch


Store and Forward

Leest het hele frame, doet een CRC check en zoek de "Destination Adress" op de MAC filter table

Cut Through

Leest tot aan het " Destination Hardware Address" en zoekt dan de "Destination Address" op in de MAC filter database

Fragment Free

Controleert de eerst 64 Bytes van een frame op fragmentatie voordat hij de frame forwards

Spanning Tree (STP) status - Posted at 14:16 on 20/1/2007 by @lfons

Status poort



  • Geen frames forwarden
  • Luistert naar BPDU
  • Alle poorten geblokkeerd (Blocked)


  • Luistert naar de BPDU om er zeker van te zijn dat er geen loops zijn en forward dan de frames


  • Leert MAC adressen en bouwt een filter tabel
  • Forward geen frames


  • Send en Receive
Ethernet Interfaces - Posted at 14:14 on 20/1/2007 by @lfons






50 Ohm Coax, 30 HOST, thinnet


185 meter


50 Ohm Coax, 1024 Host, thicknet


500 meter


2 paar UTP


100 meter


2 paar UTP


100 meter


Multimode fiber


400 meter


Shielded Twisted Pair (STP)


25 meter


4 paar UTP


100 meter


Multimode fiber 780nm laser


260 meter


SM fiber 1300nm Laser


3 – 10 km





Ethernet II Frame - Posted at 14:13 on 20/1/2007 by @lfons














Destination Address

Source Address



Frame Check Sequence -CRC

Ethernet encapsulation - Posted at 14:12 on 20/1/2007 by @lfons


application Layer




Presentation Layer




Sessie Layer



TCP Header

Upper Layer Data



Transport Layer



IP Address




Network Layer







Data Link Layer



Mac Header








Physical Layer


OSI - Posted at 14:09 on 20/1/2007 by @lfons

Application Layer

  • Waar de gebruiker communiceert met de computer.
  • (WWW, E-mail, Telnet)

Presentation Layer

  • Presenteert de data naar de Application Layer
  • Zet de data om in standaard formaten (ASCII,GIF,MP3)

Sessie Layer

  • Houdt applicatie data gescheiden van andere applicatie data.
  • (NFS, SQL)

Transport Layer

  • Verzorgt een End-to-End data transport en maakt een logische verbinding van zender naar ontvanger( TCP)
  • Zorgt voor flow-control
  • Data verpakt in "segments"

Network Layer

  • Verantwoordelijk voor routing door het internetwork en voor netwerk adressering .
  • Data verpakt in "Packets".
  • Router

Data Link layer

  • Zorgt ervoor dat de berichten worden afgeleverd naar de juiste device.
  • Data verpakt in "Frames".
  • Switches en bridged

Physical Layer

  • Zorgt voor het verzenden van de I en 0
  • Data in Bits
  • Hubs

Last Page :: Next Page