CCNA :) Be a Good Network Administrator

 1.2.2 RIP V2 Features This page will discuss RIP v2, which is an improved version of RIP v1. Both versions of RIP share the following features: It is a distance vector protocol that uses a hop count metric. It uses hold down timers to prevent routing loops – default is 180 seconds. It uses split horizon to prevent routing loops. It uses 16 hops as a metric for infinite distance. RIP v2 provides prefix routing, which allows it to send out subnet mask information with the route update. Therefore, RIP v2 supports the use of classless routing in which different subnets within the same network can use different subnet masks, as in VLSM. RIP v2 provides for authentication in its updates. A set of keys can be used on an interface as an authentication check. RIP v2 allows for a choice of the type of authentication to be used in RIP v2 packets. The choice can be either clear text or Message-Digest 5 (MD5) encryption. Clear text is the default. MD5 can be used t...

1.2 RIP Version 1.2.1 RIP History This page will explain the functions and limitations of RIP. The Internet is a collection of autonomous systems (AS). Each AS is generally administered by a single entity. Each AS has a routing technology which can differ from other autonomous systems. The routing protocol used within an AS is referred to as an Interior Gateway Protocol (IGP). A separate protocol used to transfer routing information between autonomous systems is referred to as an Exterior Gateway Protocol (EGP). RIP is designed to work as an IGP in a moderate-sized AS. It is not intended for use in more complex environments. RIP v1 is considered a classful IGP. RIP v1 is a distance vector protocol that broadcasts the entire routing table to each neighbor router at predetermined intervals. The default interval is 30 seconds. RIP uses hop count as a metric, with 15 as the maximum number of hops. If the router receives information about a network, and the receiving interface belongs to th...

 1.1.6  The following are VLSM calculations for the LAN connections in Figure : Network address: 192.168.10.0 The Perth router has to support 60 hosts. That means a minimum of six bits are needed in the host portion of the address. Six bits will yield 2 6 – 2, or 62 possible host addresses. The LAN connection for the Perth router is assigned the 192.168.10.0/26 subnet. The Sydney and Singapore routers have to support 12 hosts each. That means a minimum of four bits are needed in the host portion of the address. Four bits will yield 2 4 – 2, or 14 possible host addresses. The LAN connection for the Sydney router is assigned the 192.168.10.96/28 subnet and the LAN connection for the Singapore router is assigned the 192.168.10.112/28 subnet. The KL router has to support 28 hosts. That means a minimum of five bits are needed in the host portion of the address. Five bits will yield 2 5 – 2, or 30...

1.1.5  Route aggregation with VLSM When VLSM is used,  it is important to keep the subnetwork numbers grouped together in the network to allow for aggregation. For example, networks like 172.16.14.0 and 172.16.15.0 should be near one another so that the routers only carry a route for 172.16.14.0/23. The use of classless interdomain routing (CIDR) and VLSM prevents address waste and promotes route aggregation, or summarization. Without route summarization, Internet backbone routing would likely have collapsed sometime before 1997. Figure illustrates how route summarization reduces the burden on upstream routers. This complex hierarchy of variable-sized networks and subnetworks is summarized at various points with a prefix address, until the entire network is advertised as a single aggregate route of 200.199.48.0/20. Route summarization, or supernetting, is only possible if the routers of a network use a classless routing protocol, such as OSPF or EIGRP. Classless routing pr...

1.2  RIP Version 2 1.2.1 RIP history This page will explain the functions and limitations of RIP. The Internet is a collection of autonomous systems (AS). Each AS is generally administered by a single entity. Each AS has a routing technology which can differ from other autonomous systems. The routing protocol used within an AS is referred to as an Interior Gateway Protocol (IGP). A separate protocol used to transfer routing information between autonomous systems is referred to as an Exterior Gateway Protocol (EGP). RIP is designed to work as an IGP in a moderate-sized AS. It is not intended for use in more complex environments. RIP v1 is considered a classful IGP. RIP v1 is a distance vector protocol that broadcasts the entire routing table to each neighbor router at predetermined intervals. The default interval is 30 seconds. RIP uses hop count as a metric, with 15 as the maximum number of hops. If the router receives information about a network, and the receiving interface belong...

  Configuring VLSM 1.1.6 This page will teach students how to calculate and configure VLSM. If VLSM is the scheme chosen, it must then be calculated and configured correctly. The following are VLSM calculations for the LAN connections in Figure : Network address: 192.168.10.0 The Perth router has to support 60 hosts. That means a minimum of six bits are needed in the host portion of the address. Six bits will yield 2 6 – 2, or 62 possible host addresses. The LAN connection for the Perth router is assigned the 192.168.10.0/26 subnet. The Sydney and Singapore routers have to support 12 hosts each. That means a minimum of four bits are needed in the host portion of the address. Four bits will yield 2 4 – 2, or 14 possible host addresses. The LAN connection for the Sydney router is assigned the 192.168.10.96/28 subnet and the LAN connection for the Singapore router is assigned the 192.168.10.112/28 subnet. The KL ro...

  Route aggregation with VLSM 1.1.5  When VLSM is used, it is important to keep the subnetwork numbers grouped together in the network to allow for aggregation. For example, networks like 172.16.14.0 and 172.16.15.0 should be near one another so that the routers only carry a route for 172.16.14.0/23. The use of classless interdomain routing (CIDR) and VLSM prevents address waste and promotes route aggregation, or summarization. Without route summarization, Internet backbone routing would likely have collapsed sometime before 1997. Figure illustrates how route summarization reduces the burden on upstream routers. This complex hierarchy of variable-sized networks and subnetworks is summarized at various points with a prefix address, until the entire network is advertised as a single aggregate route of 200.199.48.0/20. Route summarization, or supernetting, is only possible if the routers of a network use a classless routing protocol, such as OSPF or EIGRP. Classless routing proto...

 Calculating subnets with VLSM 1.1.4 VLSM helps to manage IP addresses. This page will explain how to use VLSM to set subnet masks that fit the link or segment requirements. A subnet mask should satisfy the requirements of a LAN with one subnet mask and the requirements of a point-to-point WAN with another. The example in Figure shows a network that requires an address scheme. The example contains a Class B address of 172.16.0.0 and two LANs that require at least 250 hosts each. If the routers use a classful routing protocol, the WAN link must be a subnet of the same Class B network. Classful routing protocols such as RIP v1, IGRP, and EGP do not support VLSM. Without VLSM, the WAN link would need the same subnet mask as the LAN segments. A 24-bit mask of 255.255.255.0 can support 250 hosts.   The WAN link only needs two addresses, one for each router. That means that 252 addresses would be wasted. If VLSM was used, a 24-bit mask would still be applied on the LAN segments for ...

When to Use VLSM 1.1.3  It is important to design an address scheme that allows for growth and does not waste addresses. This page examines how VLSM can be used to prevent the waste of addresses on point-to-point links. As shown in Figure , the network management team has decided to avoid the wasteful use of the /27 mask on the point-to-point links. The team applies VLSM to the address problem. To apply VLSM to the address problem, the team breaks the Class C address into subnets of variable sizes. Large subnets are created for LANs. Very small subnets are created for WAN links and other special cases. A 30-bit mask is used to create subnets with only two valid host addresses. This is the best solution for the point-to-point connections. The team will take one of the three subnets they previously decided to assign to the WAN links, and subnet it again with a 30-bit mask. In the example, the team has taken one of the last three subnets, subnet 6, and subnetted it again. This time th...