circuit identifier suboption and the remote ID suboption to the relay agent information and forwards them to a DHCP server. The following explains the DHCP relay services process:
  1. The DHCP client generates a DHCP request and broadcasts it on the network.
  2. The DHCP relay agent intercepts the broadcast DHCP request packet and inserts the relay agent information option (82) in the packet. The relay agent option contains the related suboptions.
  3. The DHCP relay agent unicasts the DHCP packet to the DHCP server.
  4. The DHCP server receives the packet and uses the suboptions to assign IP addresses and other configuration parameters and forwards them back to the client.
  5. The suboption fields are stripped off of the packet by the relay agent while forwarding to the client.
Figure lists the option support commands.
Content 5.5 DHCP 5.5.10 Verifying DHCP Relay Services Figure lists useful DHCP verification commands. Figure describes the commands and parameters.
Content 5.6 Route Optimization Lab Exercises 5.6.1 Lab 5-1 Redistribution Between RIP and OSPF
Lab Activity Lab Exercise: Lab 5-1 Redistribution Between RIP and OSPF Two online booksellers, Example.com and Example.net, have merged and now need a short-term solution to interdomain routing. Since these companies provide client services to Internet users, it is essential to have minimal downtime during the transition. Example.com is a small firm running RIP, while Example.net has a somewhat larger network running OSPF. The diagram identifies R2 as the router that will bridge the two networks. Since it is imperative that the two booksellers continuously deliver Internet services, you should bridge these two routing domains without interfering with each router’s path through its own routing domain to the Internet. The CIO determines that it is preferable to keep the two protocol domains pictured in the diagram during the transition period, because the network engineers on each side need to understand the other’s network before deploying a long-term solution. Redistribution will not be your long-term solution, but will suffice as a short-term solution. Configure the topology above in a lab to verify the short-term solution. In this scenario, R1 and R2 are running RIPv2, but the 172.16.23.0/24 network between R2 and R3 is running OSPF. You need to configure R2 to enable these two routing protocols to interact to allow full connectivity between all networks.
Content 5.6 Route Optimization Lab Exercises 5.6.2 Lab 5-2 Redistribution Between EIGRP and OSPF
Lab Activity Lab Exercise: Lab 5-2 Redistribution Between EIGRP and OSPF Model the same physical topology as Route Optimization Lab 5.1. R1 is running EIGRP, and R3 is running OSPF. Add R2 to enable these two routing protocols to interact, allowing full connectivity between all networks.
Content 5.6 Route Optimization Lab Exercises 5.6.3 Lab 5-3 Redistribution Between EIGRP and IS-IS
Lab Activity Lab Exercise: Lab 5-3 Redistribution Between EIGRP and IS-IS R1 is running EIGRP, and R3 is running IS-IS. Configure R2 to enable these two routing protocols to interact to allow full connectivity between all networks. Then filter routes from each of the routing protocols using various methods.
Content 5.6 Route Optimization Lab Exercises 5.6.4 Lab 5-4 Manipulating Administrative Distances
Lab Activity Lab Exercise: Lab 5-4 Manipulating Administrative Distances In this lab, you will compare two routing protocols in how efficient they are at selecting routes, as well as what happens when you manipulate administrative distances in the routing table.
Content 5.6 Route Optimization Lab Exercises 5.6.5 Lab 5-5 Configuring the Cisco IOS DHCP Server
Lab Activity Lab Exercise: Lab 5-5 Configuring the Cisco IOS DHCP Server In this lab, R3 will not be assigned an IP address. Instead, it gets one from Dynamic Host Configuration Protocol (DHCP). R1 will demonstrate the use of the ip helper-address command.
Content Summary This module covered IP route redistribution and the control of redistributed routing updates. It also covered using passive interfaces and route maps for this control. Route maps for PBR was also discussed. Finally, using a Cisco IOS device, such as a DHCP server, relay agent, or client, was described. Any two IP routing protocols can be redistributed. However, many types of incorrect information may be propagated. Passive interfaces, distribute lists, and route maps are some of the methods used to control these updates. Route maps may also be used to implement PBR for cost savings, quality of service (QoS), and other purposes driven by enterprise policy. Although DHCP is not a true route optimization technique, it is an advanced Cisco IOS feature. It can be configured on a Cisco IOS device as a DHCP server, DHCP relay agent, or DHCP client. The ip helper-address command triggers the use of a Cisco IOS device as a relay agent, and numerous additional options can be implemented.