Cisco Reference

Guide

By Frank Hall

By Frank Hall

Table of Contents

NETWORKING: THE BASICS ............................................ 4

THE OPEN SYSTEM INTERCONNECTION (OSI) MODEL ..... 5

DEVICES ......................................................................... 6

THE HUB ......................................................................... 6

SWITCHES ...................................................................... 6

ROUTERS ........................................................................ 7

NETWORKING: CABLES ................................................... 8

CABLE TYPES ................................................................. 8

NETWORKING: CABLING CONFIGURATION FOR CONNECTING NETWORK

DEVICES ......................................................................... 9

STRAIGHT THROUGH VS. CROSSOVER ......................... 10

NETWORKING: THE BASICS SUMMARY ......................... 10

SUBNETTING FINDING HOSTS AND SUBNETS ................ 11

SO WHAT ARE HOSTS AND SUBNETS? .......................... 11

By Frank Hall

SUBNET ADDRESS: HOW ARE THEY CONSTRUCTED? ... 11

IP ADDRESSES: THE DIVIDE BETWEEN HOSTS AND SUBNETS 12

FINDING THE SUBNETS: THE MATH PART ..................... 14

FINDING THE HOSTS PER SUBNET: THE MATH PART .... 14

SUBNETTING: SUMMARY ............................................... 16

CISCO COMMANDS ........................................................ 17

CREATE VLAN ON CISCO SWITCH ................................. 26

NETWORKING CHEAT SHEETS ...................................... 29

IPV4 SUBNETTING LONG SHEET ................................... 31

IPV6 LONG SHEET ........................................................ 32

COMMON COMMUNICATION PORTS .............................. 34

PHYSICAL TERMINATORS ............................................. 36

By Frank Hall

Networking: The Basics

In this lesson we are going to cover the very basics of computer networking. This is the bare

essentials you need to know before moving on to Cisco networking. This will cover the

different types of cables, cable types, interconnecting Cisco network devices and finally the

OSI model.

By Frank Hall

The Open System Interconnection (OSI) model

The Open System Interconnection (OSI) model defines the network process function. This

includes components of networking and data transmission. When you understand how the

OSI Model works you will understand how everything can communicate in a network. The

table below depicts the seven layers and what each layer does.

Devices

The Hub A hub is the dumbest network device. It does not have any memory. It is not

configurable. Most importantly is does not route. All a hub does is connect two or more

computers, receives a transmission signal, amplifies the signal, and sends to every

By Frank Hall

computer on the hub. Unlike a switch or router when a hub transmits a signal it goes out

every port, or what is called multicast.

Switches Switches are more intelligent than a hub and is used to connect multiple devices on the

same network. Unlike a hub, a switch has memory that can store configurations. The

network switch handles packets of data differently than a hub, sending specific data to the

computer it is sending the data.

By Frank Hall

Routers

In a network topology, the router is at the top. The router is the most intelligent networking

device. A router is more intelligent than hubs and switches because it has memory, security,

maintains routing information, and is configurable. A router transmits data from one

computer network to another. Unlike switches and hubs, the router routes packages to the

network along with local computers. It is used to communicate through networks. All

connections go to the router.

By Frank Hall

Networking: Cables

Cable Types There are many types of cables that are used for networking computers and network

devices together. The three most common cables that are used today are CAT-5/CAT-5e,

CAT-6, and Fiber Optic. The cable type we will be using is CAT-5 and the configurations of

this cable that are used on the hubs, switches and routers.

1 - CAT-5/CAT-5e

2 CAT-5 Cable is a twisted pair cable that used for a structured computer networks. There are eight twisted

pairs of copper wiring in a CAT-5 Cable. The twisting of the cables reduces the electrical interference and

crosstalk between the cables. CAT-5 supports 10Base-T, 100Base-T, and 1000Base-T transfer rate speed.

By Frank Hall

3 - CAT-6

CAT-6 Cable is very similar to CAT-5 in appearance but the difference is how the cable handles higher transfer

rates. CAT-6 uses all four twisted pairs and supports up to 1 Gb per second. It also has additional shielding

which reduces crosstalk more than CAT-5 cable.

4 - Fiber Optic

Fiber Optic cable contains glass tubes wrapped in insulated casing and is designed for transfer speeds of

100Mbps and higher. It uses pulsating light to carry the data. Since fiber uses glass tubes and light it is less

susceptible to electrical inference and crosstalk.

Illustrations are from Verizon.com, pakistanstuff.com, citrusmicro.com

By Frank Hall

Networking: Cabling configuration for connecting network devices There are two ways to configure your CAT-5 Cable for connecting them to computers and

network devices. These two configurations are called Straight Through and Crossover. The

terms straight through and crossover refer to how the cables are arranged in the connector.

4 - A Straight through Cable is arranged the same at both ends of the cable.

5 - A Crossover Cable is similar but the transmit(TX) and receive(RX) lines are in opposite positions at the ends of the

cable.

Straight Through vs. Crossover When connecting network devices, the rule is “Same device uses a crossover. Different

device used a straight through.” As seen in these two diagrams.

By Frank Hall

Now that you know how to network devices with the correct cables this will ensure data

flow, network availability, and security are maintained at a constant rate. Know how each

cable is constructed and which device it connects to will increase in your troubleshooting

abilities.

When connecting network devices, the rule is “Same device uses a crossover. Different

device used a straight through.” As seen in these two diagrams.

Networking: The Basics summary This concludes my class on Networking the basics you need to know. You have learned

about the OSI Model, the seven layers and how data flow works according the OSI Model.

You know have the knowledge of the different network devices and how they affect data

flow on a network. Finally, you have learned about network cables, how they are

constructed, how straight through and crossover cables are constructed, and which

network device is connected using either a straight through or crossover cables.

Subnetting Finding Hosts and subnets

Knowing how to subnet a very important part of creating a computer network. You must

know how to divide your IP addresses among your routers, switches and workstations. This

is to use all your IP addresses efficiently and to ensure your network operates with as few

problems as possible. When you are creating your network you must determine the

number of hosts and subnets that will need to be used.

By Frank Hall

So what are Hosts and Subnets?

A Host in relationship to a network is a computer/device that connectivity to your network

and is able to communicate with other computer and devices. A host address is used to

identify a device that is on the network. When this host address is combined with a

network address a 32 bit IP address is created.

A Subnet or subnetwork is a subdivision of your IP network. Subnetting allows you to create

multiple logical networks that exist within a single Class A, B, or C network. If you do not

subnet, you are only able to use one network from your Class A, B, or C network, which is

unrealistic.

Subnet Address: How are they constructed?

An IPv4 address is made up of 8 bits. These 8 bits are arranged into octets. When you have

4 octets you have a full 32bit IPv4 IP address as the illustration below has displayed. Each

byte in the octet has a

place value that from 128-1. How do we get to 128 from 1? That is simple each place value

is doubled. That is to say (1+1=2, 2+2=4, 4+4=8, etc. To 128). When the IP address is

displayed in binary, as seen below, when the bit is used it is marked with a one (1). If the bit

is not needed or used it will be marked with a zero (0).

In order to figure out which octet is valued at all you need to do is to add up the place

holders that are marked with a one (1) meaning this bit is being used. As seen in the display

below in the first three octets if you add 128+64+32+16+8+4+2+1 = 255. This also indicates

that all the bits are being used in this octet. Now in the fourth octet when we add the bits

that are on which are 128+64+32+16 = 240. The subnet IP address is 255.255.255.240.

By Frank Hall

IP Addresses: The divide between Hosts and Subnets

The number of hosts or subnets depends on the Class of network. For instance, a Class

"A" network requires more hosts then subnets. A Class "C" network requires more

subnets. When determining how many hosts and subnets are needed always remember

the hosts you need the less subnets you have. The more subnets that are needed the less

hosts you have to use in your network.

The chart displays the subnet for each network class. As describes to you in the previous slide the Class "A"

network has the least number of network/subnets and the most hosts. While the Class “C" has the most

networks/subnets and the least number of hosts.

By Frank Hall

Finding the Subnets: The Math Part

When you are determining the number of subnets that are need for your network the

formula that is used is 2^n (n=number of borrowed bits from the host). No in the diagram

below we have the last two octets of out IP address displayed in the actual number and in

binary. When you apply the formula 2^n what you are calculating is the number of bits

that are being used or marked as one “1”. So our formula is 24 or 2x2x2x2 = 16. So the

number of subnets is 16.

By Frank Hall

Finding the Hosts per Subnet: The Math Part When you are determining the number of hosts per subnet that are need for your

network the formula that is used is 2^n -2 (n= number of bits in the host portion. Then we

subtract 2). In the diagram below we have the last two octets of our subnet address

displayed in the actual number and in binary. When you apply the formula 2^n -2 what

you are calculating is the number of bits that are not being used or marked as zero “0”

from the host bits. You must subtract 2 because an address consisting of all 0 bits

specifies the network, and an address of all 1 bits is used for network broadcasts. So our

formula is 24 -2 or (2x2x2x2) -2. So the number of hosts per subnet is 14.

Now that you understand how to find hosts and subnets how do you find the subnet mask when

all you have is an IP address and the number of subnets?

IP 192.168.10.0 You need 14 subnets. What is the subnet mask?

To solve this, you need to work the 2^n -2 formula in reverse. The formula will be 2^n +2. 14

subnets = 24 +2 = 16 which is the number of subnets. You use the 24 which indicates the

number of bits that are used in the subnet and add then together for the subnet address or

128+64+32+16 which is 240.

By Frank Hall

Subnetting: Summary

Now that you have reviewed this presentation you should now know how to find

Subnets, hosts per Subnet, or find the subnet mask. Of course you need to practice these

skills to keep them sharp. If you have any questions always feel free to ask.

Oh yes I nearly forgot. There is a cheat sheet on the last slide. Don’t always depend on

knowing the cheat sheet. It’s good to have when you are taking a test, it is always better to

know how to find the solution on your own.

By Frank Hall

Cisco Commands

Cisco Modes

Description Keyboard short cut

User mode

Switch>

Enter Privilege mode

Switch>enable

Privileged mode

Switch#

Enter configuration mode

Switch configure terminal

Global Config mode

Switch(config)#

Enter Interface mode

Switch(config)#interface fa0/1

Interface mode

Switch(config-if)

Return to global configuration

Switch(config-if)exit

Exit Global Config mode

Switch(config)#exit

Return to use mode

Switch#disable

Logout

Switch>exit

Keyboard Shortcuts

Description Keyboard shortcut

Recall Previous command

Up arrow or <Ctrl> p

Recall Next command

Down arrow or <Ctrl> n

Beginning of command

<Ctrl> a

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End of command

<Ctrl> e

Delete input

<Ctrl> d

Exit Configuration Mode

<Ctrl> z

Complete command

TAB

Device Configuration

Description Commands

Configure device system name

Switch(config)#hostname sw1

Sets the encrypted enable password

Switch(config)#enable secret cisco

Sets the unencrypted enable password

Switch(config)#enable password cisco

Enable password encryption on all clear text password within the configuration file

Switch(config)#service password-encryption

Configure a Message Of The Banner, with an ending character of $

Switch(config)#banner motd $

Assign IP address to vlan Switch(config)#int vlan 1 Switch(config-if)#ip addr 172.22.1.11 255.255.255.0

Assign Default gateway, note the mode

Switch(config)#ip default-gateway 10.1.1.1

Select one interface

Switch(config)#int fa0/1

Select a range of interfaces (version dependant)

Switch(config)#int range fa0/1 – 12

Set the interface description

Switch(config-if)#description

By Frank

By Frank Hall

Add vlan using config mode switch(config)#vlan 11 switch(configvlan)#name

test

Configure Interface fa0/1 @

speed 100 Mbps and full duplex

Switch(config-if)#speed 100 Switch(config-if)#duplex full

Assign interface to vlan

switch(config-if)#switchport access vlan 11

Enable Port Security. Switch(config-if)#switchport mode access Switch(config-if)#switchport port-security Switch(configif)#switchport port-security mac-address sticky

Disable Interface Switch(config-if)shutdown

Enable Interface

Switch(config-if)no shutdown

Configures 5 Telnet sessions each with a password of ‘cisco’

Switch(config)#line vty 0 4 Switch(config-line)#login Switch(config-line)#password cisco

Enable and define console

password of ‘cisco’ Switch(config)#line con 0 Switch(config-line)#login Switch(config-line)#password cisco

Synchronise console messages (keep what you have typing on the screen)

Switch(config-line)#logging synchronous

Set the timezone and automatically adjust

Switch(config)#clock timezone gmt 0 Switch(config)#clock

summer-time gmt recurring

Sets the switch priority for the vlan. This combined with the switch mac address creates the switch BID

Switch(config)#spanning-tree vlan 1 priority 4096

Enables portfast

Switch(config)#int fa0/1 Switch(config-if)#spanning-tree portfast

Enables RSTP. Other options are, PVST and MST

Switch(config)#spanning-tree mode rapid-pvst

Creates a vlan. Note this now done in config mode not vlan database. Also note the ‘int vlan’ command does NOT create vlans

Switch(config)#vlan 2 Switch(config-vlan)#name sales

By Frank Hall

Assign an interface to vlan 2

Switch(config-if)#switchport access vlan 2

Unconditionally forces an interface into trunking. Other options are access and dynamic

Switch(config-if)#switchport mode trunk

Manually assign a switch to a VTP domain. A switch will automatically become part of a VTP domain if it’s currently in the ‘null’ domain and receives a VTP frame

Switch(config)#vtp domain lab

Changes the VTP mode from the default ‘server’ mode to client mode. In client mode no changes can be made

Switch(config)#vtp mode client

Enable the http server to SDM can be used

Router(config)#ip http server

Defines a username and password. The list can be used for many things from PPP authentication to user access

Router(config)#username sue password cisco

Defines a local host file. Like /etc/hosts in unix

Router(config)#ip host mypc 10.1.1.3

Disables DNS lookup. Useful when a command as been miss typed

Router(config)#no ip domain-lookup

Sets the logical (not

physical) bandwidth of interface. This is used by

routing protocols, SNMP queuing etc

Router(config)#int s0 Router(config-if)#bandwidth

Sets the physical clock

Router(config-if)#clock rate 64000

Set the serial interface WAN encapsulation. Other options are PPP or frame-relay

Router(config-if)#encapsulation hdlc

Authentication on PPP is optional. This command enable chap on the interface. Other option PAP

Router(config-if)#ppp authentication chap

By Frank Hall

Defines the type of LMI being used. If left unconfigured the correct LMI type should be automatically detected

Router(config-if)#frame-relay lmi-type cisco

Defines a static route. Renumber static routes have an admin distance of 1. Therefore will over ride any dynamic routing.

Router(config)#ip route 50.0.0.0 255.0.0.0 10.1.2.1

Enables RIP version 1 on all LOCAL interfaces which have a 10.x.x.x address Enables RIP version 2

Router(config)#router rip Router(config-router)#network 10.0.0.0 Router(config-router)#version 2

Enable the router to provide a

DHCP service. Router(config)#ip dhcp pool MYPOOL Router(dhcp-config)#network 10.1.1.0 255.255.255.0 Router(dhcp-config)#default-router 10.1.1.1 Router(dhcp-config)#exit Router(config)#ip dhcp excluded-address 10.1.1.1

10.1.1.99

Changes the config register

which controls what the Router(config)#config-register 0x2102

router does when the router boots

Creates a logical sub interface below the physical interface Enables 802.1q trunking on the interface Define the ip address

Router(config)#int fa0/0.1

Router(config-subif)#encapsulation dot1Q 1

Router(config-subif)#ip address 10.1.1.1 255.255.255.0

Enable OSPF on any local interface which start with the ip address 10.1.x.x. Note the inverted mask

Router(config-)#router ospf 1 Router(config-router)#network 10.1.0.0 0.0.255.255 area 0

EIGRP can be configured in a similar way to RIP or the mask option could be used

Router(config)#router eigrp 1 Router(config-router)#network 172.16.0.0 Or Router(config-router)#network 172.16.2.0 0.0.0.255

Defines a standard ACL. Standard ACL use number 1-99

Router(config)#access-list 1 permit 172.16.1.1

Defines an Extended ACL. The

first address is the source IP

address

Router(config)#access-list 101 deny tcp host 172.16.1.1 host 172.16.2.1 eq telnet Router(config)#access-list 101 permit ip any any

By Frank Hall

Use the group command to attach an ACL to an interface. is used under an interface if the ACL is to filter traffic

Router(config)#interface fa0/0 Router(config-if)#ip access-group 1 out

An example using named ACL

in stead of numbers Router(config)#ip access-list extended my_list Router(config-ext-nacl)# deny tcp host 172.16.1.1 host 172.16.2.1 eq ftp Router(config-ext-nacl)# permit ip any any

Attaching a named ACL to an

interface Router(config)#int fa0/0 Router(config-if)#ip access-group my_list in

Configuring a static NAT to allow a server to be access via the Internet, using the IP address on interface s0/0/1

Router(config)#ip nat inside source static 10.1.1.2 interface s0/0/1

Defining interface which NAT takes place between

Router(config)#int fa0/0.1 Router(config-if)#ip nat inside

Enables RIPng Router(config)#ipv6 unicast-routing ROuter(config)#ipv6 router rip ccna

Router(config)#int s0/0/0 Router(config-if)#ipv6 rip ccna enable

Privilege Commands

Description Commands Manually starts the setup dialog which is automatically invoked when the device starts with no config

Switch#setup

Displays the config held in DRAM. Which is lost if not copy run start command is not used

Switch#show running-config

Displays the NVRAM (None volatile) config.

Switch#show startup-config

Saves the config. Without this

command all

changes/configuration will be

lost.

Switch#copy running-config startup-config

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Saves the running config to a TFTP server

Switch#copy running-config tftp

Copies IOS files to a TFTP server

Switch#copy flash tftp

Copies files from a TFTP server the device flash

Switch#copy tftp flash

Erase the config held in NVRAM. If this is followed with the reload command all configuration is lost

Switch#erase startup-config

Reboots the device

Switch#reload

Abort sequence

<Shift> <Ctrl> 6

Suspend Telnet Session

<Shift> <Ctrl> 6(then let all keys go, then)x

Show the current sessions. The one with a * is your active session

Switch#show sessions

Forcible closes a telnet session

Switch#disconnect

Set the device local clock.

Note this is not done in

config mode

Switch#clock set 10:00:00 april 2 2008

Display the IOS version along with other useful info e.g sys uptime, config register etc

Switch#show version

Displays the file contents of the flash

Switch#show flash

Displays the clock

Switch#show clock

Displays the users currently logged on

Switch#show users

ault displays the last 10 commands

Switch#show history

Displays the ARP cache

Switch#show arp

By Frank Hall

Displays the spanning tree status on vlan 1

Switch#show spanning-tree vlan 1

Lists all the configured vlans

Switch#show vlan

Displays VTP info such as VTP

mode, VTP domain, VTP counter.

Switch#sh vtp status

Ping selected address

Switch#ping 10.1.1.1

Extended ping. Must be in privilege mode

Switch#ping

Display the interface status

Switch#show int fa0/1

Displays the vlan status and the IP address VLAN 1 (often the management vlan)

Switch#show interfaces vlan 1

Displays a list of CDP neighbours

Switch#show cdp neighbors

Extended information on the above

Switch#show cdp neighbors details

Display CDP packets as they arrive

Switch#debug cdp packets

Display ping packets as they arrive

Switch#debug icmp packets

Display switch MAC Addresses table. These entries are learnt from the source mac address in the Ethernet frames

Switch#show mac address-table

Displays the interface operational status and IP addresses for all router interfaces

Router#show ip interface brief

Displays all the configured routing protocols

Router#show ip protocols

Displays the IP routeing table

Router#show ip route

Displays the NAT translations

Router#show ip nat translations

By Frank Hall

Displays the physical cable DTE/DCE, x.21, V.35, RS232 configuration

Router#show controllers s 0

Displays the end-to-end status. Recall that ‘show interface’ does not

Router#show frame-relay pvc

Displays the type of LMI and the number LMI frames

Router#show frame-relay lmi

Displays the frame relay inverse ARP table

Router#show frame-relay map

To be come neighbours both the local and remote interface must be correctly configured.

Router#show ip ospf neighbor

If adjacent routers don’t become neighbours. Then use the command to check the local router interface is configured correctly

Router#show ip ospf interface

Same information as the above OSPF commands but with EIGRP. Remember that AS numbers MUST match

Router#show ip eigrp neighbor

Same information as the above OSPF commands but with EIGRP

Router#show ip eigrp interface

IPv6 ping. Recall that :: means all zero in between

Router#ping 2000:1000:500:3::1

By Frank Hall

Create VLAN on Cisco Switch If you are planning to have only one network in your whole switch (for example, 10.10.192.0). i.e.

All the ports in the switch will be connected to the 10.10.192.0 network, then you don’t need to

create a VLAN, just use the default VLAN 1.

Every switch comes with the default VLAN 1 as shown below. In this example, all the ports in this

switch (from 1 through 8) are part of the default VLAN 1.

• #show vlan

VLAN Name Status Ports

---- -------------------------------- --------- ------------

1 default active Gi1/0/1, Gi1/0/2, Gi1/0/3, Gi1/0/4

Gi1/0/5, Gi1/0/6, Gi1/0/7, Gi1/0/8

In the following example, we are creating 192 VLAN network (for 10.10.192.0 network). While

creating a VLAN you also need to specify the range of ports from the switch that needs to be part of

this VLAN network.

In this example, ports 3 through 6 are configured as part of 192 VLAN network.

By Frank Hall

• config t

• vlan 192

• interface range gigabitEthernet 1/0/3-6

• switchport access vlan 192

• exit

In the above commands:

• config t – Goes into the configuration mode

• vlan 192 – Creates VLAN 192

• interface range gigabitEthernet 1/0/3-6 – Indicates that the port numbers 3 through 6 are

assigned to this VLAN

• swithport access vlan 192 – Indicates that the access to the vlan 192 is enabled

Apart from providing the access to the vlan 192 for the port numbers 3 through 6, you can also

specify the following additional switchport configuration parameters (for example, nonegotiate

and mode access)

• config t

• interface range gigabitEthernet 1/0/3-6

• switchport mode access

• switchport nonegotiate

• exit

Once you’ve created a VLAN verify it as shown below,

• #show vlan

VLAN Name Status Ports

---- -------------------------------- --------- ------------

1 default active Gi1/0/1, Gi1/0/2, Gi1/0/7, Gi1/0/8

192 VLAN0192 active Gi1/0/3, Gi1/0/4, Gi1/0/5, Gi1/0/6

Delete VLAN on Cisco Switch

You might want to delete a VLAN, if you are planning to switch the ports assigned to VLAN 192 to a

different VLAN. Or, you might want to delete a VLAN, just because you’ve created it by mistake.

Let us assume that you want to delete the VLAN 192 (ports 3 through 6) that you just

created.

Deleting a VLAN is as simple as assigning the default VLAN 1 to the ports that are part of the VLAN

you want to delete, and delete the VLAN.

By Frank Hall

i.e. If you want to delete VLAN 192, assign VLAN 1 to the ports 3 through 6, and just delete the

VLAN 192.

First, assign the default VLAN 1 to ports 3 through 6 as shown below.

• interface range gigabitEThernet 1/0/3-6

• switchport access vlan 1

• exit

Next, delete the vlan itself as shown below.

• no vlan 192

Finally, verify that the VLAN 192 got deleted as shown below.

• #show vlan

VLAN Name Status Ports

---- -------------------------------- --------- ------------

1 default active Gi1/0/1, Gi1/0/2, Gi1/0/3, Gi1/0/4

Gi1/0/5, Gi1/0/6, Gi1/0/7, Gi1/0/8

If you don’t know what you are doing, do not execute any of the above commands on

production switch, as you might bring down your network.

6 - Here is a step by step tutorial on configuring a VLAN.

By Frank Hall

Networking Cheat Sheets

By Frank Hall

By Frank Hall

By Frank Hall

By Frank Hall

By Frank Hall

Notes

Notes

By Frank Hall

Notes

By Frank Hall