Monday

CONCEPT ROUTER

 
Why is it necessary routerBefore we learn more about how to configure router cisco, we need to understand better about some basic rulesrouting. Also of course we must understand the numbering system IP, subnetting, netmasking and his brothers.
Case in point:
Host X à 128.1.1.1 (ip Class B network id 128.1.x.x)
Host Y à 128.1.1.7 (IP
Class B network id 128.1.x.x)
Host Z à 128.2.2.1 (IP
Class B network id 128.2.x.x)
In the case above, the host of X and Y can communicate directly to the host but neither the hosts X and Y can not communicate with host Z, because they have Id a different network. How so Z can communicate with X and Y?use a router!
Examples of cases using subnetting
Contoh kasus menggunakan subnetting
Host P à 128.1.208.1 subnet mask 255.255.240.0
Host Q à 128.1.208.2 subnet mask 255.255.240.0
Host R à 128.1.80.3 subnet mask 255.255.240.0
when subnetting used, then the two hosts are connected to the segment The same network can communicate only if both the network id and his subnetid sesuai.Pada case above, P and Q can communicate with Direct, R has the same network id with P and Q but has subnetidyang different. Thus R can not communicate directly with P and Q. How so R can communicate with the P and Q?use a router!  
So a router function, it can be said easily, connect two different networks, precisely directs the best route to achieve the expected network In implementation, the router is often used to connect a network between institutions or companies, each of which has a network with en a different network. Another example is when the currently popular Your company will be connected to the internet. Then the router will function stream of data packets from your company to other institutions via the Internet, of course, your network number would be calm with you company headed. If you simply connect two network units, in fact you can also using pc-based Windows NT or Linux. By providing two network units card and a bit of setting, you actually have to make practical router. Yet of course with all its limitations. 
In the router market is very diverse brands, among others baynetworks, 3Com and Cisco. The course modules we will discuss cisco special. Why? because cisco a router that is widely used and many become the standard for product other. 
More info on routing 
The data from the devices connected to the Internet are sent in the form of a datagram, ie the data packet defined by the IP. Datagram has a destination address data packet; Internet Protocol check this address to deliver datagrams from device to device origin destination. If the datagram destination address is located one network with the home device, datagram sent directly to the device goal. If you find that the datagram  destination address does not exist in the network Similarly, the datagram be submitted to the appropriate  router (the best available router). 
IP Router (usually called routers only) are devices that perform functions forward IP datagrams on the network layer. Router has more than one antamuka network (network interface) and can forward a datagram from one interface to another interface. For each datagram is received, the router check whether it is intended to datagram itself. If it turns out addressed to the router, the datagram is delivered to the transport layer.If the datagram not addressed to the router, which will be examined is its forwarding table to decide where the datagram should be are addressed. Forwarding table is a table consisting of pairs IP address (host address or network address), following the router address, and interface where the datagram out.If you do not find even a single line in the forwarding table that is in accordance with destination address, the router will give a message to the sender that the address referred to can not be achieved. This incident may be analogous to the message "Return to sender" on mail. A router can also tell you that he is not the best router to a destination, and suggested the use of routers another. With all three functions contained on this router, the hosts on the Internet can be connected to each other. 
Static and Dynamic 
In general, routing coordination mechanisms can be divided into two: the routing static and dynamic routing. In static routing, the entries in the forwarding router table is filled and removed manually, while in the dynamic routing changes made through routing protocols. Static routing settings are The simplest routing can be done on a computer network.Using pure static routing in a network means to fill every entries in forwarding tables in each router in the network.Use of static routing in a small network of course is not a problems; only a few entries that need to be filled on a forwarding table in each router. But you can certainly imagine what if must be complete the forwarding table at each router that the amount is small in large networks. Especially if you are assigned to fill the entries in all routers on the Internet that a lot of numbers and counting every day. Of course trouble at all!Dynamic routing is a means used to remove the obligation to fill forwarding table entries manually. Routing protocol set routers that can communicate with each other and each other provides routing information that can change the contents of the forwarding table, depending on the state of its network. In this way, the routers know The last state of the network and can forward the datagram in the right direction.
Interior Routing Protocol
In the early 1980s, the Internet is limited to the ARPANET, Satnet (expansion of the ARPANET  using  satellites), and several local networks connected via gateways. During its development, the Internet requires a hierarchical structure for  anticipate that the network has to be big. Internet was then divided  into several autonomous system (AS) and the current Internet consists of thousands of U.S.. Every U.S. has a mechanism for exchanging and collecting information  routing itself. A protocol used to exchange routing information in the U.S. classified as an interior routing protocol (IRP). The result of this routing information collection then submitted to the U.S. in the form of reachability information. Reachability information is issued by a U.S. contains information about networks that can be achieved through the U.S. and it became local information in the form of distance-vector to all the links directly connected with it. The router receives routing information to calculate distance-vector, adding a distance-vector with the link metric information is accepted, and put it into the forwarding table entries if  is considered one of the best lines. After the addition of routing information metric then sent back to the router interface, and this is done every certain time interval. So forth so that all routers in the network knowing the network topology. Distance-vector protocols have weaknesses which can be visible when the there is a broken network link. Two possible failures that may occur is the bounce effect and count-until-no-till (counting to infinity). Bounce effects can occur in networks that use different metrics at least a link. Broken link can cause routing loops, so that the datagram that passes through a particular link just circling between the two routers (bounce) until the age (time to live) the datagram is finished. Compute-to-no-till occurs because the router was too late to inform that a link is lost. This delay causes the router must send and receive distance-vector and calculate the metrics up to the limit distance-vector metrics achieved. Otherwise end after the link distance-vector reached the maximum metric. At the time of calculating this metric also occur routing loops, even for a longer time than if .. bounce effect ' RIP does not adopt a distance-vector protocol for granted, but with made several additions to the algorithmic order routing loop occurs can be minimized. RIP Split horizon is used to minimize the effects bounce. Split horizon principle used is simple: if node A deliver datagram to the destination X through node B, then B does not make sense for to achieve the goal of X by A. So, A does not need to tell B that X A. B can be achieved through To prevent cases of counting-to-no-till, RIP method Triggered Updates. RIP has a timer to know when the router must re- provide routing information. When changes in the network, while timer has not been exhausted, the router must still send the routing information for triggered by such changes (triggered updates). Thus, routers in the network can quickly find out the changes that occur and minimize the possibility of routing loops occur. RIP is defined in RFC-1058 using the metric between 1 and 15, while 16 are considered as no-till. Route 16 with a distance-vector is not incorporated into the forwarding table. This 16 metric limit prevents time count-until-no-till is too long. RIP packets are normally sent every 30 seconds or faster if there are triggered updates. If within 180 seconds a route is not maintained, the router route delete from the forwarding table. RIP subnets have no information about U.S. connection of the indicator to the Internet. Submission of reachability information inter-AS conducted using protocols that are classified as exterior routing protocol (ERP). IRP is used as standard on the Internet today is routing Information Protocol (RIP) and Open Shortest Path First (OSPF). In addition to these two There are also protocols that are proprietary routing protocols but widely used on the Internet, namely Internet Gateway Routing Protocol (IGRP) from Cisco Systems. IGRP protocol was later expanded into the Extended IGRP (EIGRP). All of the above routing protocols use metrics as a basis for determine the best path that can be taken by the datagram. Metrics associated with "cost" that exists in every link, which may be a throughput (Speed data), delay, connection costs, and reliability of the link. I. Routing Information Protocol RIP (acronym, pronounced as a rip) included in the distance-vector protocol, a very simple protocol. Distance-vector protocol is often too called Bellman-Ford protocol, because it comes from the distance calculation algorithm shortest by R.E. Bellman, and described in the form first-time distributed algorithm by Ford and Fulkerson. Each router with distance-vector protocol when first run only know how routing to itself (local information) and not know where he is the network topology. Later sends Router  each route. Router must consider each received a subnet route The same with the router's subnet. Thus, RIP does not support Variable Length Subnet Masking (VLSM). RIP version 2 (RIP-2 or RIPv2) attempt to produce some improvement of RIP, namely support for VLSM, using authentication, provides next hop information (next hop), and multicast. Additional information on the subnet mask in each route to make the router do not have to assume that the route has the same subnet mask subnet mask used him. RIP-2 also uses authentication in order to know where the routing information that can be trusted. Authentication is required on the routing protocols to make become more secure protocol. RIP-1 does not use authentication so people can give a false routing information. Next hop information in RIP-2 is used by routers to inform a route but to achieve the routes were not past the router that provides information, but the other router. Use the following hops are usually at the border inter-AS. RIP-1 uses the broadcast address for sending routing information. As a result, this packet is received by all hosts within the subnet and increase the workload of the host. RIP-2 can transmit packets using IP multicast on 224.0.0.9 so that not all hosts need to receive and process the routing information. Only the routers that use RIP-2 accept routing information without the need to disrupt other hosts in subnet. RIP is a simple routing protocol, and this is the reason why RIP most widely implemented in the network. Set the routing using RIP is not complicated and gives quite acceptable results, especially when network link failures are rare. However, for networks large and complex, RIP may not be enough. In this condition, RIP routing in the calculation often requires a long time, and cause routing loops. For such networks, most using a computer network specialist who entered the protocol group link-state II. Open Shortest Path First (OSPF) Link-state technology developed to produce a protocol ARPAnet distributed a lot better than distance-vector protocol. Instead of exchanging distance (distance) to the destination, each router in the network has a network map that can be updated quickly after each topology changes. This map is used to calculate a more accurate route instead of using distance-vector protocol. The development of this technology eventually produce protocol Open Shortest Path First (OSPF) developed by the IETF for use on the Internet. Even now the Internet Architecture Board (IAB) has recommended OSPF instead of RIP.
The principle of link-state routing is very simple. As a replacement to calculate route "Best" by way of distributed, all routers have a network map and count all the best routes from this map. Network map stored in a database and each record in the database specifies a link in the network. The records are transmitted by routers that connect directly with each link. Because each router need to have a network map that describes the conditions last complete network topology, any changes in the network must followed by a change in link-state databases located at each router. Link status changes are detected the router will change the database link-state router, then the router sends these changes to other routers. A protocol used to transmit this change must be rapid and can be reliable. This can be achieved by a flooding protocol. In the flooding protocol, message sent is a change from the database as well as the serial number of the message these. By only sending data base changes, the time required for sending and processing messages fewer dibandingdengan send the entire contents of the database. Serial number of messages required for know whether the new message is received more than there are in database. This serial number handy in case of broken links to be connected back. At the moment there are broken links and networks into a separate, second database into different parts of the network. When these links are broken lives again, the data base on all routers must be equated. This database will not back together by sending a link-state messages only. Equalization process data base on the neighboring router is called the turn adjacency. Two neighbors called the adjacent routers when link-state database both have been the same. In this process the two routers are not mutually exchanging data base because it will take a long time. Process switch consists of two fasa.Fasa adjacency first, second router exchanging database description is a summary of the data base owned by each router. Each router then compares the description basis of data received by its data base. In the second phase, each router to ask her neighbors to send the records database different, ie if the router has no such record, or serial number records that are owned less than that delivered by the description of base data. After this process, the router was updating some records and then sent to other routers via flooding protocol. Link-state protocol better than distance-vector protocol is caused by several things: the time needed to converge faster, and more importantly, this protocol does not produce routing loops. This Protocol support the use of multiple metrics at once. Throughput, delay, cost, and reliability metrics which are commonly used in the network. The principle of link-state routing is very simple. As a replacement to calculate route "Best" by way of distributed, all routers have a network map and count all the best routes from this map. Network map stored in a database and each record in the database specifies a link in the network. The records are transmitted by routers that connect directly with each link. Because each router need to have a network map that describes the conditions last complete network topology, any changes in the network must followed by a change in link-state databases located at each router. Link status changes are detected the router will change the database link-state router, then the router sends these changes to other routers. A protocol used to transmit this change must be rapid and can be reliable. This can be achieved by a flooding protocol. In the flooding protocol, message sent is a change from the database as well as the serial number of the message these. By only sending data base changes, the time required for sending and processing messages fewer dibandingdengan send the entire contents of the database. Serial number of messages required for know whether the new message is received more than there are in database. This serial number handy in case of broken links to be connected back. At the moment there are broken links and networks into a separate, second database into different parts of the network. When these links are broken lives again, the data base on all routers must be equated. This database will not back together by sending a link-state messages only. Equalization process data base on the neighboring router is called the turn adjacency. Two neighbors called the adjacent routers when link-state database both have been the same. In this process the two routers are not mutually exchanging data base because it will take a long time. Process switch consists of two fasa.Fasa adjacency first, second router exchanging database description is a summary of the data base owned by each router. Each router then compares the description basis of data received by its data base. In the second phase, each router to ask her neighbors to send the records database different, ie if the router has no such record, or serial number records that are owned less than that delivered by the description of base data. After this process, the router was updating some records and then sent to other routers via flooding protocol. Link-state protocol better than distance-vector protocol is caused by several things: the time needed to converge faster, and more importantly, this protocol does not produce routing loops. This Protocol support the use of multiple metrics at once. Throughput, delay, cost, and reliability metrics which are commonly used in the network. 
In addition, this protocol can also generate a lot of routes to a destination. Suppose A router has two channels with the same metrics to host B. Protocol can enter these two lines into the forwarding table so that the router able to divide the load between the two routes. Draft OSPF uses link-state protocols with some additional functions. The added functions such as support networks multi-access, such as X.25 and Ethernet, and divide large networks form the some areas. Has been described above that each router in link-state protocols need form adjacency with the neighboring router. On multi-access network, neighbors of each router can be more than one. In situations like this, every routers in the network need to establish adjacency with all other routers, and is inefficient. OSPF adjacency minimize this by introducing the concept of designated routers and backup designated routers. All routers only needed adjacent to the designated router, so that only designated router is adjacent to all other routers. Designated router reserves will take over the functions of a designated router that failed to function. The first step in a multi-access network is to choose a designated router and reserves. This election is inserted into the Hello protocol, the protocol in OSPF neighbors to know the router in each link. After election, then the routers to form adjacency with the designated routers and back up. Any changes in the network, the router sends message using the flooding protocol to the designated router, and a designated router which sends the message to the other routers in the link. Designated router reserves also listen to the messages sent to designated router. If the designated router fails, back up and then become newly designated router and selected a new backup designated router. Because the new router has been designated adjacent to the other routers, is not necessary anymore equalization process that requires time database the old. In a large network of large data base is needed also for save the network topology. This leads to the router memory requirements larger as well as route calculation time is longer. To anticipate this case, OSPF uses the concept of area and backbone. Network is divided into some areas that were connected to the backbone. Each area is considered as a network separate and routers in it only needs to have a topology map network in these areas. Routers located on the border between area only to send a summary of the links contained in the area and topology does not send one area to another area. Thus, the calculation becomes much simpler route. Simplicity vs.. Ability 
We already see at a glance how the RIP and OSPF work. Any protocol routing has advantages and disadvantages of each. Protokol RIP very simple and easy to implement but can lead to routing loops.OSPF protocol is a protocol that is more complicated and better than RIP but requires memory and CPU time are great.In many places there are also using a combination of routingstatic, RIP, RIP-v2, and OSPF. The results in this network show that static routing administration far more time consuming than dynamic routing. Observations on the dynamic routing protocols also show that RIP uses greater bandwidth than the OSPF and the bigger the network, bandwidth used RIP grow larger as well. So, if you are designing TCP / IP network is a great course OSPF routing protocol selection appropriate.


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