Friday, July 18, 2008

Uses of the OSI Model

You should be familiar with the OSI model, because it is the most widely used method for talking about network communications. However, remember that it is only a theoretical model that defines standards for programmers and network administrators, not a model of actual physical layers.

Using the OSI model to discuss networking concepts has the following advantages:

Provides a common language or reference point between network professionals
Divides networking tasks into logical layers for easier comprehension
Allows specialization of features at different levels
Aids in troubleshooting
Promotes standards interoperability between networks and devices
Provides modularity in networking features (developers can change features without changing the entire approach)

However, you must remember the following limitations of the OSI model.

OSI layers are theoretical and do not actually perform real functions.
Industry implementations rarely have a layer-to-layer correspondence with the OSI layers.
Different protocols within the stack perform different functions that help send or receive the overall message.
A particular protocol implementation may not represent every OSI layer (or may spread across multiple layers)

Available Commands

User/Privileged Exec Commands

  • clear frame-relay-inarp
    configure terminal
    copy running-config startup-config
    copy startup-config running-config
    disable
    disconnect
    enable
    exit
    help
    ping
    show cdp
    show cdp interface
    show cdp interface
    show cdp neighbors
    show cdp neighbors
    show configuration
    show controllers
    show frame-relay lmi
    show frame-relay map
    show frame-relay pvc
    show frame-relay route
    show history
    show interfaces
    show interfaces (including bri0:1, bri0:2)
    show ip access-lists
    show ip interface
    show ip interface
    show ip route
    show ipx route
    show ipx servers
    show isdn active
    show isdn history
    show isdn status
    show running-config
    show startup-config
    show version
    terminal editing
    terminal history
    terminal history size
    terminal no editing
    terminal no history
    traceroute

Global Configuration Commands

  • access-list <1-99> deny/permit

    access-list <1-99> deny/permit

    access-list <1-99> deny/permit host

    banner
    banner exec
    banner incoming
    banner login
    banner motd
    cdp holdtime

Serial Interface Commands

  • cdp enable
    clock rate
    description
    encapsulation frame-relay
    encapsulation hdlc
    encapsulation ppp
    exit
    frame-relay interface-dlci
    frame-relay inverse-arp
    frame-relay map ip

    help
    ip access-group <1-99>
    ip address

    ipx network

    ipx network
    encapsulation
    ipx network
    encapsulation secondary
    shutdown


BRI Commands

  • description
    dialer fast-idle
    dialer idle-timeout
    dialer map ip

    dialer string
    dialer-group
    exit
    help
    ip address

    isdn spid1
    isdn spid2
    isdn switch-type
    shutdown


Line/Console Commands

  • exit
    help
    login
    password
    Router Commands
    network


Switch User/Privileged Mode Commands

  • configure
    configure terminal
    disable
    enable
    exit
    help
    ping
    show cdp
    show cdp interface
    show cdp interface
    show cdp neighbors
    show cdp neighbors
    show history
    show interfaces
    show interfaces
    show ip
    show running-config
    show spanning-tree
    show spanning-tree
    show version
    show vlan
    show vlan
    show vlan-membership
    show vtp


Switch Global Commands

  • cdp holdtime
    cdp timer
    enable password level 15
    end
    exit
    help
    hostname
    interface
    ip address

    ip default-gateway

    spanning-tree ...
    switchport access vlan
    vlan
    vlan name
    vtp client/server/transparent


Switch Ethernet/Fast Ethernet Commands

  • cdp enable
    description
    exit
    help
    shutdown
    vlan-membership static

Friday, July 11, 2008

Network Engineer Career Profile

Network Engineer - Overview
A Network Engineer is involved in the design and maintenance of both the hardware and software necessary for a computer network. They are high level technical analysts with a specialty in Local Area Networks (LANs) or Wide Area Networks (WANs).

Education for Network Engineers
Many colleges now offer degrees in Network Engineering. The University of Colorado at Boulder, for example, has a great reputation. Drexel University offers a graduate degree in Electrical and Computer Engineering. There are now MBA programs that specialize in Network Management, such as the program offered by If you are looking for an online program for Network Engineering, Westwood College offers a BS in Network Engineering.

Becoming a Network Engineer
Network Engineers usually have a Bachelors degree or higher. They may have had internships or specialty projects within the Network Design and Engineering field. There are often positions to start out in, with increasing responsibility and specialization as you acquire years of experience and specialty certifications.

Career Paths for Network Engineers
Network Engineers are typically promoted to senior level engineers and may focus extensively on specialty areas such as design, performance optimization or network security. Compensation for Network Engineers is excellent. Many of the top paying jobs within the IT field are in Network Engineering. Several of the in Information Technology are within the Networking realm.

Companies Hiring Network Engineers
It seems like everyone is hiring Network Engineers these days! Some of the larger companies that currently have openings include:
Cisco Systems
Microsoft Corporation
Google
Apple Computers
The US Government
Yahoo
Amazon.com
eBay
Network Engineering Links
Links to useful information about Network Engineering, including top industry sites to stay current in the filed:
NetworkComputing.com
IEEE
Electronics and Engineering Network