Cisco IOS IP Configuration Guide, Release 1. Configuring IP Addressing Cisco IOS Software Releases 1. Simple Atm Program In Turbo CourtMainline Configuring IP Addressing This chapter describes how to configure IP addressing. For a complete description of the IP addressing commands in this chapter, refer to the IP Addressing Commands chapter of the Cisco IOS IP Command Reference, Volume 1 of 3 Addressing and Services publication. To locate documentation of other commands that appear in this chapter, use the command reference master index, or search online. IP Addressing Task List A basic and required task for configuring IP is to assign IP addresses to network interfaces. Doing so enables the interfaces and allows communication with hosts on those interfaces using IP. Associated with this task are decisions about subnetting and masking the IP addresses. To configure various IP addressing features, perform the tasks described in the following sections. The task in the first section is required the tasks in remaining sections are optional. Assigning IP Addresses to Network Interfaces Required Configuring Address Resolution Methods Optional Enabling IP Routing Optional Enabling IP Bridging Optional Enabling Integrated Routing and Bridging Optional Configuring a Routing Process Optional Configuring Broadcast Packet Handling Optional Configuring Network Address Translation Optional Monitoring and Maintaining IP Addressing Optional At the end of this chapter, the examples in the IP Addressing Examples section illustrate how you might establish IP addressing in your network. Assigning IP Addresses to Network Interfaces An IP address identifies a location to which IP datagrams can be sent. Some IP addresses are reserved for special uses and cannot be used for host, subnet, or network addresses. Table 3 lists ranges of IP addresses, and shows which addresses are reserved and which are available for use. Table 3 Reserved and Available IP Addresses. Class. Address or Range. Status. A 0. 0. 0. Reserved. Available. Reserved B 1. 28. Available. Reserved C 1. Reserved. Available. Reserved D 2. 24. Multicast group addresses E 2. C has three major decision making instructionsthe if statement, the ifelse statement, and the switch statement. The if Statement C uses the keyword if to. Subscribe and SAVE, give a gift subscription or get help with an existing subscription by clicking the links below each cover image. Simple Atm Program In Turbo CarsIssuu is a digital publishing platform that makes it simple to publish magazines, catalogs, newspapers, books, and more online. Easily share your publications and get. Fiery Remote Scan 6. Reserved. Broadcast The official description of IP addresses is found in RFC 1. Internet Numbers. To receive an assigned network number, contact your Internet service provider ISP. An interface can have one primary IP address. To assign a primary IP address and a network mask to a network interface, use the following command in interface configuration mode. Command. Purpose. Routerconfig if ip addressip address mask Sets a primary IP address for an interface. A mask identifies the bits that denote the network number in an IP address. When you use the mask to subnet a network, the mask is then referred to as a subnet mask. Note We only support network masks that use contiguous bits that are flush left against the network field. The tasks to enable or disable additional, optional, IP addressing features are contained in the following sections Assigning Multiple IP Addresses to Network Interfaces Enabling Use of Subnet Zero Disabling Classless Routing Behavior Enabling IP Processing on a Serial Interface Assigning Multiple IP Addresses to Network Interfaces Cisco IOS software supports multiple IP addresses per interface. You can specify an unlimited number of secondary addresses. Secondary IP addresses can be used in a variety of situations. The following are the most common applications There might not be enough host addresses for a particular network segment. For example, suppose your subnetting allows up to 2. Using secondary IP addresses on the routers or access servers allows you to have two logical subnets using one physical subnet. Many older networks were built using Level 2 bridges, and were not subnetted. The judicious use of secondary addresses can aid in the transition to a subnetted, router based network. Routers on an older, bridged segment can easily be made aware that many subnets are on that segment. Two subnets of a single network might otherwise be separated by another network. You can create a single network from subnets that are physically separated by another network by using a secondary address. In these instances, the first network is extended, or layered on top of the second network. Note that a subnet cannot appear on more than one active interface of the router at a time. Note If any router on a network segment uses a secondary address, all other routers on that same segment must also use a secondary address from the same network or subnet. To assign multiple IP addresses to network interfaces, use the following command in interface configuration mode. Abbreviation acronyms Term Definition CGREX Chaos Game Representation Explorer a handy Bioinformatics tool for exploring the sequence visualization and pattern. The Texarkana Gazette is the premier source for local news and sports in Texarkana and the surrounding Arklatex areas. Bank Accounts Open a Bank Account Online Easily open a bank account in minutes and make money management simple. Enjoy a bank account with the flexibility you need. If you want to do your taxes online, HR Block can help. Learn more about our online tax preparation options and get started today. Get your weekly DIY fix with our customized newsletter. Thanks Youve been added to our list. Good stuff is on its way Book Title. Cisco IOS IP Configuration Guide, Release 12. Chapter Title. Configuring IP Addressing. PDF Complete Book 6. MB PDF This. Command. Purpose. Routerconfig if ip addressip address masksecondary Assigns multiple IP addresses to network interfaces. Note IP routing protocols sometimes treat secondary addresses differently when sending routing updates. See the description of IP split horizon in the Configuring IP Enhanced IGRP, Configuring IGRP, or Configuring RIP chapters for details. See the Creating a Network from Separated Subnets Example section at the end of this chapter for an example of creating a network from separated subnets. Enabling Use of Subnet Zero Subnetting with a subnet address of 0 is illegal and strongly discouraged as stated in RFC 7. For example, if network 1. You can use the all 0s and all 1s subnet 1. Configuring interfaces for the all 1s subnet is explicitly allowed. However, if you need the entire subnet space for your IP address, use the following command in global configuration mode to enable subnet 0. Command. Purpose. Routerconfig ip subnet zero Enables the use of subnet zero for interface addresses and routing updates. Disabling Classless Routing Behavior By default, classless routing behavior is enabled on the router. When classless routing is in effect, if a router receives packets destined for a subnet of a network that has no network default route, the router forwards the packet to the best supernet route. In Figure 1, classless routing is enabled in the router. Therefore, when the host sends a packet to 1. Figure 1 IP Classless Routing If you disable classless routing, and a router receives packets destined for a subnet of a network that has no network default route, the router discards the packet. Figure 2 shows a router in network 1. Suppose the host sends a packet to 1. Because there is no network default route, the router discards the packet. Figure 2 No IP Classless Routing To prevent the Cisco IOS software from forwarding packets destined for unrecognized subnets to the best supernet route possible, use the following command in global configuration mode. Command. Purpose. Routerconfig no ip classless Disables classless routing behavior. Enabling IP Processing on a Serial Interface You might want to enable IP processing on a serial or tunnel interface without assigning an explicit IP address to the interface. Whenever the unnumbered interface generates a packet for example, for a routing update, it uses the address of the interface you specified as the source address of the IP packet. It also uses the specified interface address in determining which routing processes are sending updates over the unnumbered interface. Restrictions are as follows Serial interfaces using High Level Data Link Control HDLC, PPP, Link Access Procedure, Balanced LAPB, and Frame Relay encapsulations, as well as Serial Line Internet Protocol SLIP tunnel interfaces, can be unnumbered.