Router Information Protocol

RIP Stability Features RIP prevents routing loops from continuing indefinitely by implementing a limit on the number of hops allowed in a path from the source to a destination. The maximum number of hops in a path is 15. If a router receives a routing update that contains a new or changed entry, and if increasing the metric value by 1 causes the metric to be infinity (that is, 16), the network destination is considered unreachable. The downside of this stability feature is that it limits the maximum diameter of a RIP network to less than 16 hops. RIP includes a number of other stability features that are common to many routing protocols. These features are designed to provide stability despite potentially rapid changes in a network's topology. For example, RIP implements the split horizon and holddown mechanisms to prevent incorrect routing information from being propagated.

Routing Updates

How Routing Portocol Sends Routing-Update

---

RIP sends routing-update messages at regular intervals and when the network topology changes. When a router receives a routing update that includes changes to an entry, it updates its routing table to reflect the new route. The metric value for the path is increased by 1, and the sender is indicated as the next hop. RIP routers maintain only the best route (the route with the lowest metric value) to a destination. After updating its routing table, the router immediately begins transmitting routing updates to inform other network routers of the change. These updates are sent independently of the regularly scheduled updates that RIP routers send.

Background of Routing Information Protocol

Routing Information Protocol (RIP)

---

The Routing Information Protocol, or RIP, as it is more commonly called, is one of the most enduring of all routing protocols. RIP is also one of the more easily confused protocols because a variety of RIP-like routing protocols proliferated, some of which even used the same name! RIP and the myriad RIP-like protocols were based on the same set of algorithms that use distance vectors to mathematically compare routes to identify the best path to any given destination address. These algorithms emerged from academic research that dates back to 1957.

Today's open standard version of RIP, sometimes referred to as IP RIP, is formally defined in two documents: Request For Comments (RFC) 1058 and Internet Standard (STD) 56. As IP-based networks became both more numerous and greater in size, it became apparent to the Internet Engineering Task Force (IETF) that RIP needed to be updated. Consequently, the IETF released RFC 1388 in January 1993, which was then superceded in November 1994 by RFC 1723, which describes RIP 2 (the second version of RIP). These RFCs described an extension of RIP's capabilities but did not attempt to obsolete the previous version of RIP. RIP 2 enabled RIP messages to carry more information, which permitted the use of a simple authentication mechanism to secure table updates. More importantly, RIP 2 supported subnet masks, a critical feature that was not available in RIP.

Hyper Terminal Setup in Window

HYPER TERMINAL

From windows

1). Click on programs

2). Click on Accessories

3). Select hyper terminal if available. If it does not appear on the list of accessory programs, then go to How to install Hyper terminal.

---

HOW TO SET UP WINDOWS HYPER TERMINAL

1) In hyper terminal create a "new connection" this can be done by clicking the Hypertrm.exe icon or via the menu within HyperTerminal "File:NewConnection".

2) Type in a name for the connection (for example, cyq504).

3) Under "connect using" select "Direct to Com 2" if your available com port is com 2 otherwise select the appropriate com port. (Modems are relentlessly selfish about interrupts. So if a modem is present then avoid the modem port and it's cousin. That is, if the modem is on com 1 then avoid both com 1 and 3. Com 1 and 3 share an interrupt while com 2 and 4 share a different interrupt; in this case avoid 2 and 4)

4) Set "Bits per second" to 9600.

5) Set "Data Bits" to 8.

6) Set "Stop Bits" to 1.

7) Set "Flow control" to None.

8) Click OK - the hyper terminal screen should appear.

9). Select properties from the menu bar.

10) Click on "settings", use default: autodetect and back scroll 500 lines.

11) For "ASCII setup" use

a). Sending - check: "echo typed characters locally" box. This lets you see the commands you type in.

b). Receiving - check: "append line feeds" and "wrap long lines". The CyQ module emits a carriage return (CR), but no line feed. This keeps data from being overwritten on the screen.

11) Under "File" menu select "Save As" and save the configuration file to a convenient folder.

You can create a shortcut to the configuration file and put it on the desktop, this makes life a bit simpler. The configuration files have a naming convention of *.ht where star is the name you chose when setting up the new connection. For example, "cyq504.ht".

Cisco Router Configuration Commands

Cisco Router Configuration Commands

Configuration of router is a routine when setting-up networkng. During our lab practice we are give the command, but in reality, if you need to set-up a network, it involved router. Configuration of router is a must, understanding of some basic commands will be an advantage.

Here is a link to read more of the Cisco router configurating commands :

Cisco Router Commands

Learn to Subnet

Video Tutorial on IP Addressing and Subnetting

Subnetting is a very basic requirement for setting up networking. You may have to take some time to understand the whole issue of ip addressing and subnetting. Learn from Video tutorial.

IP Packet Header

The Internet Protocol (IP) uses a Datagram service to transfer packets of data between end systems using routers. The IP packet header consists of 20 bytes of data. An option exists within the header that allows further optional bytes to be added, but this is not normally used (with the occasional exception of something called "Router Alert"). The full header is shown below: The header fields are discussed below: Version (always set to the value 4, which is the current version of IP) IP Header Length (number of 32 -bit words forming the header, usually five) Type of Service (ToS), now known as Differentiated Services Code Point (DSCP) (usually set to 0, but may indicate particular Quality of Service needs from the network, the DSCP defines the way routers should queue packets while they are waiting to be forwarded). Size of Datagram (in bytes, this is the combined length of the header and the data) Identification ( 16-bit number which together with the source address uniquely identifies this packet - used during reassembly of fragmented datagrams) Flags (a sequence of three flags (one of the 4 bits is unused) used to control whether routers are allowed to fragment a packet (i.e. the Don't Fragment, DF, flag), and to indicate the parts of a packet to the receiver) Fragmentation Offset (a byte count from the start of the original sent packet, set by any router which performs IP router fragmentation) Time To Live (Number of hops /links which the packet may be routed over, decremented by most routers - used to prevent accidental routing loops) Protocol (Service Access Point (SAP) which indicates the type of transport packet being carried (e.g. 1 = ICMP; 2= IGMP; 6 = TCP; 17= UDP). Header Checksum (A 1's complement checksum inserted by the sender and updated whenever the packet header is modified by a router - Used to detect processing errors introduced into the packet inside a router or bridge where the packet is not protected by a link layer cyclic redundancy check. Packets with an invalid checksum are discarded by all nodes in an IP network) Visit My Other blog on Creating a Blog Body Care Kits Acknowledge Your Spouse

What is an IP address?

Every machine on the Internet has a unique identifying number, called an IP Address. A typical IP address looks like this:

216.27.61.137 To make it easier for us humans to remember, IP addresses are normally expressed in decimal format as a "dotted decimal number" like the one above. But computers communicate in binary form. Look at the same IP address in binary:

11011000.00011011.00111101.10001001 The four numbers in an IP address are called octets, because they each have eight positions when viewed in binary form. If you add all the positions together, you get 32, which is why IP addresses are considered 32-bit numbers. Since each of the eight positions can have two different states (1 or 0) the total number of possible combinations per octet is 28 or 256. So each octet can contain any value between 0 and 255. Combine the four octets and you get 232 or a possible 4,294,967,296 unique values!

Out of the almost 4.3 billion possible combinations, certain values are restricted from use as typical IP addresses. For example, the IP address 0.0.0.0 is reserved for the default network and the address 255.255.255.255 is used for broadcasts.

The octets serve a purpose other than simply separating the numbers. They are used to create classes of IP addresses that can be assigned to a particular business, government or other entity based on size and need. The octets are split into two sections: Net and Host. The Net section always contains the first octet. It is used to identify the network that a computer belongs to. Host (sometimes referred to as Node) identifies the actual computer on the network. The Host section always contains the last octet. There are five IP classes plus certain special addresses:

Default Network - The IP address of 0.0.0.0 is used for the default network.

Class A - This class is for very large networks, such as a major international company might have. IP addresses with a first octet from 1 to 126 are part of this class. The other three octets are used to identify each host. This means that there are 126 Class A networks each with 16,777,214 (224 -2) possible hosts for a total of 2,147,483,648 (231) unique IP addresses. Class A networks account for half of the total available IP addresses. In Class A networks, the high order bit value (the very first binary number) in the first octet is always 0. Net Host or Node 115. 24.53.107

Loopback - The IP address 127.0.0.1 is used as the loopback address. This means that it is used by the host computer to send a message back to itself. It is commonly used for troubleshooting and network testing.

Class B - Class B is used for medium-sized networks. A good example is a large college campus. IP addresses with a first octet from 128 to 191 are part of this class. Class B addresses also include the second octet as part of the Net identifier. The other two octets are used to identify each host. This means that there are 16,384 (214) Class B networks each with 65,534 (216 -2) possible hosts for a total of 1,073,741,824 (230) unique IP addresses. Class B networks make up a quarter of the total available IP addresses. Class B networks have a first bit value of 1 and a second bit value of 0 in the first octet. Net Host or Node 145.24. 53.107

Class C - Class C addresses are commonly used for small to mid-size businesses. IP addresses with a first octet from 192 to 223 are part of this class. Class C addresses also include the second and third octets as part of the Net identifier. The last octet is used to identify each host. This means that there are 2,097,152 (221) Class C networks each with 254 (28 -2) possible hosts for a total of 536,870,912 (229) unique IP addresses. Class C networks make up an eighth of the total available IP addresses. Class C networks have a first bit value of 1, second bit value of 1 and a third bit value of 0 in the first octet. Net Host or Node 195.24.53. 107

Class D - Used for multicasts, Class D is slightly different from the first three classes. It has a first bit value of 1, second bit value of 1, third bit value of 1 and fourth bit value of 0. The other 28 bits are used to identify the group of computers the multicast message is intended for. Class D accounts for 1/16th (268,435,456 or 228) of the available IP addresses. Net Host or Node 224. 24.53.107

Class E - Class E is used for experimental purposes only. Like Class D, it is different from the first three classes. It has a first bit value of 1, second bit value of 1, third bit value of 1 and fourth bit value of 1. The other 28 bits are used to identify the group of computers the multicast message is intended for. Class E accounts for 1/16th (268,435,456 or 228) of the available IP addresses. Net Host or Node 240. 24.53.107

Broadcast - Messages that are intended for all computers on a network are sent as broadcasts. These messages always use the IP address 255.255.255.255.

Visit My Other blog on Creating a Blog
Body Care Kits
Acknowledge Your Spouse

Basic Network Design

The most common form of network is Ethernet. This is a bus-like network that uses Carrier-Sense Multiple Access with Collision Detection (CMSA-CD). Interpreting this we have a network where stations apply a voltage to the bus when they wish to send data, by sensng the bus for this voltage we can determine if the bus is in use; multiple access implies many hosts may be on this bus; collision detect is used to detect multiple hosts sending data at the same time. Initially, it would seem unnecessary to need collision detection, after all, a station on sends data on the bus when there is no one else sending. Due to the propagation delay of electrical signals we can have to stations decide to send data at the same time, when each station looks at the bus it is clear, however before the data they send reaches it's destination they will collide and the result will be garbage. The collision detection circuitry monitors the line to verify there were no collisions and the data does not need to be resent. Understanding the CMSA-CD concept is fundamental to understanding how ethernet works. All limitations found on the design of ethernet networks are there do to issues surrounding CMSA-CD. The biggest design limitation is that reading data on an ethernet is a passive operation, the sending stations has no way to "sense" when this has happened. However, the sending station must perform collision detection until it knows the receiving station has gotten the packet! To do, lenght restrictions must be developed so that a sending station knows that within a finite time the receiving stations must have gotten the packet. This time limit controls most aspects of network design. A basic way of calculating this time limit is to look at how long a machine must monitor the network is to look at the underlying physics. By it's definition ethernet operates at a speed of 10 Mhz (10 million bits/sec). The maximum packet size is 1500 bytes (12,000 bits). Presently ethernet has a maximum lenght of 500 meters. The time required to transmit 1500 bytes over 500 meters is: Time to transmit a packet is 12000 bits/10,000,000 bits/sec is .0012 seconds Time to transmit a bit 500 meters is defined by the speed that electrical signals travel, which is the speed of light. This figure turns out to be : 500 meters / 60000 meters/sec which equaks .0008333 seconds Other characteristics that define ethernet deal with the waveform that a ethernet signal assumes. The waveform on a thick ethernet segment is 2.5 meters in lenght, that is why stations are seperated by 2.5 meters. Ethernet HardwareEthernet has evolved over time. Ethernet version 2 released in 1982 was originally developed by Xerox-Intel-Dec. In 1985 the IEEE released a new standard for ethernet. This standard is named IEEE 802.2. In general, these two versions of ethernet can inter-operate, however there are a few minor differences. The first difference is that in the ethernet packet header Version 2 defined a two byte Type field while IEEE created a 2 byte length field in that location. Luckily, values for type cannot conflict with valid length values and most systems can determine the Ethernet Frame type by examining this field. A second difference was that the Ethernet version 2 spec required that a transciever send a heartbeat signal each second. The IEEE 802.2 spec removed this. This has resulted in most vendors offerring transcievers that have a switch to enable or disable hearbeat. It should be off unless connected to a piece of equipment using the ethernet version 2 spec. Luckily, all new devices are built to conformto the 802.2 spec; however there are occasionally devices found that were installed years ago that still need this. In either specification, ethernet uses a 48 bit identifier to uniquely identify each source and destination device.A range of addresses is assigned to each manufactuer of ethernet equipment. There are basically two categories of ethernet components, one type that passes the signal onto other devices, generally these are known as repeaters. A secondtype of device which takes the signal and regenerates the signal onto a new network, these types of devices are generally known as bridges or routers. Repeaters are useful for propagating a network signal, a signal comes in on an input port is often output to many ports.However since they add some delay to the transmittal of packets they reduce the maximum size a segment can be. However, repeaters can simplify the design of a network. Devices such as bridges and routers, which regenerate the signal, allow you to build larger networks. Since the signal is regenerated, it becomes the responsibility of the bridge or router to gaurentee the packets arrival at the destination (or the next router or bridge). Bridges and routers work at different levels of the network. Bridges work at the ethernet frame level while routers work at the protocol level. In both cases, the bridge or router, has the property of filtering traffic and only transmitting the signal onto networks where it makes sense. Thus, in each case they have the effect of reducing unnecessary traffic.

Software Componets of TCP/IP

Application Layer

---

Some of the applications we will cover are SMTP (mail), Telnet, FTP, Rlogin, NFS, NIS, and LPD

Transport Layer

---

The transport uses two protocols, UDP and TCP. UDP which stands for User Datagram Protocol does not gaurentee packet delivery and applications which use this must provide their own means of verifying delivery. TCP does gaurentee delivery of packets to the applications which use it.

Network Layer

---

The network layer is concerned with packet routing and used low level protocols such as ICMP, IP, and IGMP.In addition, routing protocols such as RIP, OSPF, and EGP will be discussed.

Link Layer

---

The link layer is concerned with the actual transmittal of packets as well as IP to ethernet address translation.This layer is concerned with Arp, the device driver, and Rarp. Over the next few months we will be examining these components as we work our way up from the bottom. First, we need to get a basic upderstanding of how networks are designed and how the basic hardware used to interconnect them.

INTRODUCTION TO TCP/IP

TCP/IP is made up of two acronyms, TCP, for Transmission Control Protocol, and IP, for Internet Protocol. TCP handles packet flow between systems and IP handles the routing of packets. However, that is a simplistic answer that we will expound on further. All modern networks are now designed using a layered approach. Each layer presents a predefined interface to the layer above it. By doing so, a modular design can be developed so as to minimize problems in the development of new applications or in adding new interfaces. The ISO/OSI protocol with seven layers is the usual reference model. SInce TCP/IP was designed before the ISO model was developed it has four layers; however the differences between the two are mostly minor. Below, is a comparison of the TCP/IP and OSI protocol stacks: OSI Protocol Stack 7. Application -- End user services such as email. 6. Presentation -- Data problems and data compression 5. Session -- Authenication and authorization 4. Transport -- Gaurentee end-to-end delivery of packets 3. Network -- Packet routing 2. Data Link -- Transmit and receive packets 1. Physical -- The cable or physical connection itself. TCP/IP Protocol Stack. 5. Application -- Authenication, compression, and end user services. 4. Transport -- Handles the flow of data between systems and provides access to the network for applications via the (BSD socket library) 3. Network -- Packet routing 2. Link -- Kernel OS/device driver interface to the network interface on the computer. Below are the major difference between the OSI and TCP/IP: The application layer in TCP/IP handles the responsibilities of layers 5,6, and 7 in the OSI model. The transport layer in TCP/IP does not always gaurentee reliable delivery of packets as the transport layer in the OSI model does. TCP/IP offers an option called UDP that does not gaurentee reliable packet delivery.

SUBNETTING

TCP/IP - Subnetting

---

I can recalled during my reprofiling days, we do came across subnetting. Back to current, in day 1, AM session, Mr Foo touch on the subnetting, I really can't catch how he derive the number of subnetting give the number of subnetting that are needed for a network.At home, I spent one hour of self study on the note given, and I managed to grasp a little. Not till the next morning (Day 2) before going to class, I managed to fully understand how to derive subnetting. What Is Subnetting Subnetting is the process of allocating bits from the host portion as a network portion. For example, giving the class A network 10.0.0.0 a subnet mask of 255.255.0.0 would break it down into 256 sub-networks (10.0.0.0 to 10.0.255.0), and indicates that the first octet of the IP address shows the network address, the second one shows the subnet number and the last two show the host part. A bitwise AND operation of the host address with the subnet mask extracts the complete subnetwork address (see example below). Subnet masks are not limited to whole octets, either. For example 255.254.0.0 (or /15) is also a valid mask. Applied to a class A address this would create 128 subnetworks in intervals of two (1.2.0.1 - 1.3.255.254, 1.4.0.1 - 1.5.255.254, etc).

Continue Our 40 Hrs of Learning

Hi Colleauge, Today we just finished part of the 40 hours clocking. What we learned for the past 3 days are very technical stuff which some of us have no experience at all. But nevermind, we have to continue our learning process and to better understand the past 3 days lesson, I purposely created this blog to exchange our experience and secret weapons learnt from those 3 days. This can also act as part of revision, those stuff that we went through have to keep it somewhere and practice it. I hope that these blog can encourage all of us to exchange what we learnt during our 40 hours.

---

Table of Contents

---

Enterprise Network Design and Implementation

Chapter	Course Outline	Day
1	TCP/IP Concepts Introduction to TCP/IP protocol IP Header IP Addressing and Subnetting IP Address Allocation Exercisese: Fixed and Variable Length Subnetting(Ex 1) Hyperterminal Setup and Cisco Router Access (Lab1) Introduction to CISCO Router Command Line Interface (Lab2)	One
2	Routing Protocol Objective of Routing Types of routing protocols Static and dynamic routing Distance-Vector vs Link-State Link-State routing protocol Static route implementation Implementation of RIP-based routing(Lab4) Implementation of IGRP routing(Lab5) Configuration OSPF routing process (Lab6)	Two
3	Enhancement to IP Services Dynamic Host Configuration Protocol (DHCP) DHCP across various segments Private addresses and Network Address Translation(NAT) Implementation of Router-based DHCP Service(Lab7) NAT Implementations(lab8)	Three