IP Subnet Table

Class A

Number of bits borrowed	Number of usable subnets	Number of usable IPs	Subnet Mask
2	4	4mt	255.192.0.0
3	8	2mt	255.224.0.0
4	16	1mt	255.240.0.0
5	32	524t	255.248.0.0
6	64	262t	255.252.0.0
7	128	131t	255.254.0.0
8	256	65,536	255.255.0.0

Class B

Number of bits borrowed	Number of usable subnets	Number of usable IPs	Subnet Mask
2	4	16,380	255.255.192.0
3	8	8,190	255.255.224.0
4	16	4,094	255.255.240.0
5	32	2,046	255.255.248.0
6	64	1,022	255.255.252.0
7	128	510	255.255.254.0
8	256	254	255.255.255.0

Class C

Number of bits borrowed	Number of usable subnets	Number of usable IPs	Subnet Mask
2	4	60	255.255.255.192
3	8	30	255.255.255.224
4	16	14	255.255.255.240
5	32	6	255.255.255.248
6	64	2	255.255.255.252

TCP/IP Subnet Table

Prefix	Subnet Mask	Number of Hosts	Networks (Class B) *	Networks (Class C) *	Inverse Mask +	Notes
/16	255.255.0.0	65534	1		0.0.255.255	Class B
/17	255.255.128.0	32766	0+1		0.0.127.255	In Class A networks, CIDR, or subnet-zero enabled networks only
/18	255.255.192.0	16382	2+1		0.0.63.255
/19	255.255.224.0	8190	6+1		0.0.31.255
/20	255.255.240.0	4090	14+1		0.0.15.255
/21	255.255.248.0	2046	30+1		0.0.7.255
/22	255.255.252.0	1022	62+1		0.0.3.255
/23	255.255.254.0	510	126+1		0.0.1.255
/24	255.255.255.0	254	254+1	1	0.0.0.255	Class C
/25	255.255.255.128	126	510+1	0+1	0.0.0.127	in class B or larger networks, CIDR, or subnet-zero enabled networks only
/26	255.255.255.192	62	1022+1	2+1	0.0.0.63
/27	255.255.255.224	30	2046+1	6+1	0.0.0.31
/28	255.255.255.240	14	4090+1	14+1	0.0.0.15
/29	255.255.255.248	6	8190+1	30+1	0.0.0.7
/30	255.255.255.252	2	16382+1	62+1	0.0.0.3
/31	255.255.255.254	0				Invalid mask since it leaves no host bits
/32	255.255.255.255	1			0.0.0.0	Special single host mask

www.mindflip.com

OSI Diagram

OSI Network Architecture

Open Systems Interconnection (OSI) model is a reference model developed by ISO (International Organization for Standardization) in 1984, as a conceptual framework of standards for communication in the network across different equipment and applications by different vendors. It is now considered the primary architectural model for inter-computing and inter-networking communications. Most of the network communication protocols used today have a structure based on the OSI model. The OSI model defines the communications process into 7 layers, dividing the tasks involved with moving information between networked computers into seven smaller, more manageable task groups. A task or group of tasks is then assigned to each of the seven OSI layers. Each layer is reasonably self-contained, so that the tasks assigned to each layer can be implemented independently. This enables the solutions offered by one layer to be updated without adversely affecting the other layers.

The specific description for each layer is as follows:

Layer 7: Application Layer

• Defines interface-to-user processes for communication and data transfer in network
• Provides standardized services such as virtual terminal, file and job transfer and operations

Layer 6: Presentation Layer

• Masks the differences of data formats between dissimilar systems
• Specifies architecture-independent data transfer format
• Encodes and decodes data; encrypts and decrypts data; compresses and decompresses data

Layer 5: Session Layer

• Manages user sessions and dialogues
• Controls establishment and termination of logic links between users
• Reports upper layer errors

Layer 4: Transport Layer

• Manages end-to-end message delivery in network
• Provides reliable and sequential packet delivery through error recovery and flow control mechanisms
• Provides connectionless oriented packet delivery
• Device used - PC
  

Layer 3: Network Layer

• Determines how data are transferred between network devices
• Routes packets according to unique network device addresses
• Provides flow and congestion control to prevent network resource depletion
• Device used - Router
  

Layer 2: Data Link Layer

• Defines procedures for operating the communication links
• Frames packets
• Detects and corrects packets transmit errors
• Device used - Bridge/Switch
  

Layer 1: Physical Layer

• Defines physical means of sending data over network devices
• Interfaces between network medium and devices
• Defines optical, electrical and mechanical characteristics
• Device used - Repeater/NIC, Hub/Tranceiver
  

www.networkdictionary.com

Rollover Cable

Rollover cable (also known as Cisco console cable) is a type of null-modem cable that is most commonly used to connect a computer terminal to a router's console port. This cable is typically flat (and has a light blue color) to help distinguish it from other types of network cabling. It gets the name rollover because the pinouts on one end are literally rolled over when RJ45 plugs are used at both ends.

www.wikipedia.org

Devices can be connected by Roll-over:

Console port to Switch

Console port to Router

Cross Over Cable

Crossover Cable

Crossover cable that maps all output signals on one electrical connector to the input signals on the other connector, allowing two electronic devices to perform full-duplex communication. Most commonly, the term refers to the Ethernet crossover cable, but other cables follow the same principle. It also allows devices to communicate without a switch, hub, or router. Cross-Over cables are used to connect two computers directly through NICs without the use of a Hub or Switch or to uplink two or more hubs, switches or routers. The Pins of the RJ-45 Connectors at both ends of a cross-over cable are connected as follows:

Pin 1 ----------- Pin 3
Pin 2 ----------- Pin 6

www.wikipedia.org

Crossover used to connect same devices.

Devices can be connected by Crossover:

PC to PC

Router to Router

Switch to Switch

Hub to Hub

PC to Router

Straight-throught Cable- RJ-45 Plug

Straight-throught Cable

s

Straight-through Cable

Straight-through cable is a type of twisted pair copper wire cable for local area network (LAN) use for which the RJ-45 connectors at each end have the same pinout (i.e., arrangement of conductors).

It is identical to crossover cable, except that in the latter the wires on the cable are crossed over so that the receive signal pins on the connector on one end are connected to the transmit signal pins on the connector on the other end.

Straight-through cable is also commonly referred to as patch cable. However, this might be confusing in some situations because patch cable also has a broader definition that emphasizes the fact that there is a connector on each end rather than the equality (or lack thereof) of the pinouts.

Straight-through cable is used to connect computers and other end-user devices (e.g., printers) to networking devices such as hubs and switches. It can also be used to directly connect like devices (e.g., two hubs or two switches) if the cable is plugged into an uplink port on one (but not both) of the devices. Crossover cable is used to connect two like devices without the use of an uplink port.

www.linfo.org

Straight-through used to connect different devices.

Devices can be connected by Straight-through:

PC to Switch

PC to Hub

Switch to Router

Hub to Router

Transmission Control Protocol (TCP)

The Transmission Control Protocol (TCP) is one of the core protocols of the Internet protocol suite. TCP provides reliable, in-order delivery of a stream of bytes, making it suitable for applications like file transfer and e-mail. It is so important in the Internet protocol suite that sometimes the entire suite is referred to as "the TCP/IP protocol suite." TCP is the transport protocol that manages the individual conversations between web servers and web clients. TCP divides the HTTP messages into smaller pieces, called segments, to be sent to the destination client. It is also responsible for controlling the size and rate at which messages are exchanged between the server and the client.

www.wikipedia.org

Cisco Router Configuration Commands

Requirement	Cisco Command
Set a console password to cisco	Router(config)#line con 0 Router(config-line)#login Router(config-line)#password cisco
Set a telnet password	Router(config)#line vty 0 4 Router(config-line)#login Router(config-line)#password cisco
Stop console timing out	Router(config)#line con 0 Router(config-line)#exec-timeout 0 0
Set the enable password to cisco	Router(config)#enable password cisco
Set the enable secret password to peter. This password overrides the enable password and is encypted within the config file	Router(config)#enable secret peter
Enable an interface	Router(config-if)#no shutdown
To disable an interface	Router(config-if)#shutdown
Set the clock rate for a router with a DCE cable to 64K	Router(config-if)clock rate 64000
Set a logical bandwidth assignment of 64K to the serial interface	Router(config-if)bandwidth 64 Note that the zeroes are not missing
To add an IP address to a interface	Router(config-if)#ip addr 10.1.1.1 255.255.255.0
To enable RIP on all 172.16.x.y interfaces	Router(config)#router rip Router(config-router)#network 172.16.0.0
Disable RIP	Router(config)#no router rip
To enable IRGP with a AS of 200, to all interfaces	Router(config)#router igrp 200 Router(config-router)#network 172.16.0.0
Disable IGRP	Router(config)#no router igrp 200
Static route the remote network is 172.16.1.0, with a mask of 255.255.255.0, the next hop is 172.16.2.1, at a cost of 5 hops	Router(config)#ip route 172.16.1.0 255.255.255.0 172.16.2.1 5
Disable CDP for the whole router	Router(config)#no cdp run
Enable CDP for he whole router	Router(config)#cdp run
Disable CDP on an interface	Router(config-if)#no cdp enable

Cisco Router Show Commands

Requirement	Cisco Command
View version information	show version
View current configuration (DRAM)	show running-config
View startup configuration (NVRAM)	show startup-config
Show IOS file and flash space	show flash
Shows all logs that the router has in its memory	show log
View the interface status of interface e0	show interface e0
Overview all interfaces on the router	show ip interfaces brief
View type of serial cable on s0	show controllers 0 (note the space between the 's' and the '0')
Display a summary of connected cdp devices	show cdp neighbor
Display detailed information on all devices	show cdp entry *
Display current routing protocols	show ip protocols
Display IP routing table	show ip route
Display access lists, this includes the number of displayed matches	show access-lists
Check the router can see the ISDN switch	show isdn status
Check a Frame Relay PVC connections	show frame-relay pvc
show lmi traffic stats	show frame-relay lmi
Display the frame inverse ARP table	show frame-relay map

Cisco Router Basic Operations

Requirement	Cisco Command
Enable	Enter privileged mode
Return to user mode from privileged	disable
Exit Router	Logout or exit or quit
Recall last command	up arrow or
Recall next command	down arrow or
Suspend or abort	and and 6 then x
Refresh screen output
Compleat Command	TAB

Cisco Router Copy Commands

Requirement	Cisco Command
Save the current configuration from DRAM to NVRAM	copy running-config startup-config
Merge NVRAM configuration to DRAM	copy startup-config running-config
Copy DRAM configuration to a TFTP server	copy runing-config tftp
Merge TFTP configuration with current router configuration held in DRAM	copy tftp runing-config
Backup the IOS onto a TFTP server	copy flash tftp
Upgrade the router IOS from a TFTP server	copy tftp flash

Cisco Router Debug Commands

Requirement	Cisco Command
Enable debug for RIP	debug ip rip
Enable summary IGRP debug information	debug ip igrp events
Enable detailed IGRP debug information	debug ip igrp transactions
Debug IPX RIP	debug ipx routing activity
Debug IPX SAP	debug IPX SAP
Enable debug for CHAP or PAP	debug ppp authentication
Switch all debugging off	no debug all undebug all

www.tomax7.com

Default Logins and Passwords for Networked Devices

Packet

A packet is piece of a message transmitted over a packet-switching network. See under packet switching. One of the key features of a packet is that it contains the destination address in addition to the data. In IP networks, packets are often called datagrams.

A unit of data that is routed between an origin and a destination on the Internet or any other packet-switched network. When any file (e-mail message, HTML file, GIF file Uniform Resource Locator request, and so forth) is sent from one place to another on the Internet, the Transmission Control Protocol (TCP) layer of TCP/IP divides the file into "chunks" of an efficient size for routing. Each of these packets is separately numbered and includes the Internet address of the destination. The individual packets for a given file may travel different routes through the Internet. When they have all arrived, they are reassembled into the original file (by the TCP layer at the receiving end).

IP Address

Internet protocol (IP) is the set of techniques used by many hosts for transmitting data over the Internet. The current version of the Internet protocol is IPv4, which provides a 32-bit address system.

Internet protocol is a "best effort" system, meaning that no packet of information sent over it is assured to reach its destination in the same condition it was sent. Often other protocols are used in tandem with the Internet protocol for data that for one reason or another must have extremely high fidelity.

Every device connected to a network, be it a local area network (LAN) or the Internet, is given an Internet protocol number. This address is used to identify the device uniquely among all other devices connected to the extended network.

The current version of the Internet protocol (IPv4) allows for in excess of four billion unique addresses. This number is reduced drastically, however, by the practice of webmasters taking addresses in large blocks, the bulk of which remain unused. There is a rather substantial movement to adopt a new version of the Internet protocol (IPv6), which would have two to the one-hundred twenty-eighth power of unique addresses. This number can be represented roughly by a three with thirty-nine zeroes after it.

Subneting

Subnetting is the process of breaking down an IP network into smaller sub-networks called "subnets." Each subnet is a non-physical description (or ID) for a physical sub-network (usually a switched network of host containing a single router in a multi-router network).

Cisco CCNA subnetting tutorial

Download links:

link 1
semsim.com
link 2