Chapter 6. IP Addressing and Services

This chapter presents background and configuration information on IP addressing and IP services provided by the router, with a focus on the following topics:

• 6-1: IP Addressing and Resolution ” IP addresses must be assigned to an interface in order for the router to pass IP traffic. Although configuring addresses is fundamental to router operation, selections in subnet masks and address resolution methods also can be configured. This section covers configuring addressing and resolution methods , including ICMP Router Discovery Protocol (IRDP) configuration.

• 6-2: IP Broadcast Handling ” Many broadcasts exist within network environments, including those originated by the router. This section covers how the router can be configured to handle broadcasts it receives to provide appropriate handling. It also deals with how to change the address the router uses when it sends broadcast packets.

• 6-3: Hot Standby Router Protocol (HSRP) ” To enhance the availability of a forwarding device, the Hot Standby Router Protocol provides a method that lets multiple routers offer a single IP gateway address so that a client can still reach that address even if one router goes down. This section discusses how to configure HSRP to operate on router interfaces to provide this IP gateway redundancy.

• 6-4: Dynamic Host Configuration Protocol (DHCP) ” Dynamic Host Configuration Protocol is a client server protocol that allows clients to be configured with the appropriate IP configuration parameters via the DHCP server. This section discusses how to configure the router to act as a DHCP server and shows how the configurations of pools interact with one another.

• 6-5: Mobile IP ” With the introduction of more and more wireless technologies, it is becoming important to manage IP addressing for "roaming" users, who might travel to different access points in the network. This section describes how to configure mobile IP services so that mobile or "roaming" users can maintain their IP addresses wherever they are connected to the network.

• 6-6: Network Address Translation (NAT) ” Because of the exhaustion of IP addresses and the need to provide private addressing for management and security reasons, it is important to be able to provide private addressing while providing connectivity to public networks. Network address translation allows the router to provide a method to translate between private and public addresses. This section deals with the setup and configuration of NAT.

• 6-7: Server Load Balancing (SLB) ” A router can act as a virtual server on behalf of a server farm of real servers. SLB provides load balancing of connections across the servers in the server farm. SLB can also detect server failures, control access to the servers, and collect server capacity data.