Configuring the Dhcp Relay Agent | Cisco Systems OL-4580-01 instruction

C H A P T E R 8

Configuring the DHCP Relay Agent

The Dynamic Host Configuration Protocol (DHCP) servers provide configuration parameters to DHCP clients. When DHCP clients and associated servers do not reside on the same IP network or subnet, a DHCP relay agent can transfer DHCP messages between them. To configure a DHCP relay agent on a CSS, define DHCP server destinations on a circuit and enable the DHCP relay agent on the circuit.

You must first assign an IP address on the circuit to be able to configure the DHCP relay agent for the circuit. Use the ip address command in the specific circuit mode to assign the IP address and a subnet mask. For example:

(config-circuit[VLAN2])# ip address 178.3.6.53/8

This chapter contains the following major sections:

•DHCP Relay Agent Configuration Quick Start

•Enabling and Disabling DHCP on the Circuit

•Defining the Hops Field Value for Forwarding DHCP Messages

•Displaying the DHCP Relay Configuration

		Cisco Content Services Switch Routing and Bridging Configuration Guide

	OL-4580-01			8-1
	OL-4580-01			8-1

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Cisco Systems OL-4580-01 manual Configuring the Dhcp Relay Agent

Contents

Software Version January Copyright 2004, Cisco Systems, Inc. All rights reserved Iii N T E N T S Configuring Circuits Showing Circuits Ospf Overview Vii Setting the Retransmission Interval Viii Configuring the Internet Protocol Enabling CDP OL-4580-01 Interface Trunking Between VLANs Xii Field Description for the show bridge port-fast Command Xiv Field Descriptions for the show ospf redistribute Command Preface Xvi How to Use This GuideAudience This guide is organized as follows Xvii Related Documentation Xviii Rmon Xix TACACS+ Symbols and Conventions Xxi Obtaining DocumentationCisco.com Ordering Documentation Xxii Documentation FeedbackObtaining Technical Assistance Cisco Technical Support Website Opening a TAC Case TAC Case Priority DefinitionsXxiii Xxiv Obtaining Additional Publications and Information Xxv Xxvi Interface and Circuit Overview Configuring Interfaces and Circuits OL-4580-01 CSS Interfaces and Circuits Config# interface e1 Interface and Circuit Configuration Quick StartLog in to the CSS Enter configuration mode by typing config # config Config# circuit VLAN3 Optional Display the interface configurationOptional Display the circuit configuration Config# circuit VLAN1 Configuring Interfaces Text string from 1 to 255 characters including spaces Configuring an InterfaceCommand. For example Entering a Description for the Interface To remove an interface description, enter Configuring Interface Duplex and Speed Configuring Interfaces and Circuits Config-if1/1#phy auto-negotiate disable Setting Interface Maximum Idle Time Specifying Vlan Trunking for an Interface Bridging an Interface to a Vlan Config-trunkif2/3# no trunk To remove the default Vlan selection, enter Selecting a Default Vlan in a Trunk Configuring Interfaces and Circuits To restore the default port priority of 128, enter Configuring Spanning-Tree Bridge PathcostConfiguring Spanning-Tree Bridge Port Priority To restore the default path cost, enter Config-ife7#bridge state enable Configuring Port Fast on an InterfaceConfiguring Spanning-Tree Bridge State To disable the bridge state, enter Enabling Port Fast Config-if2/1#bridge port-fast enableConfig-if2/1#bridge port-fast disable Config# bridge bpdu-guard enabled Showing Port Fast Information Config# bridge bpdu-guard disabled Showing Bridge Configurations Showing Interface Configurations Bridge interface virtual LAN number Vlan Field Description Vlan on the port Showing Trunking ConfigurationsShowing Interface Information Port CSS port 6describes the fields in the show interface command output Config# show phy 2/1Showing Interface Duplex and Speed Showing Interface Statistics 7describes the fields in the show phy command output This object contains an octet string of zero length 8describes the fields in the show mibii command outputInterface address at the protocol layer immediately That do not have such an address for example, a serial line # clear statistics Frame check sequence FCS check Showing Ethernet Interface ErrorsNumber of frames received on the interface that are an Integral number of octets in length but do not pass Field Description Shutting Down All Interfaces Shutting Down an Interface To restart all interfaces, enter Restarting an InterfaceRestarting All Interfaces To shut down all interfaces, enter Config# circuit VLAN7 Configuring CircuitsEntering Circuit Configuration Mode Configuring a Circuit IP Interface Configuring a Circuit-IP Broadcast Address Configuring a Circuit IP Address Configuring Circuit-IP Unreachables Configuring Circuit-IP Redirects Preference To disable router discovery, enterEnabling and Disabling a Circuit IP 100 Configuring the Router-Discovery Lifetime Configuring Router-Discovery Limited-BroadcastTo revert to the default of 224.0.0.1, enter Min-advertisement-interval Configuring the Router-Discovery Max-Advertisement-IntervalConfiguring the Router-Discovery Min-Advertisement-Interval Max-advertisement-interval 10describes the fields in the show circuits command output Showing CircuitsTo list an individual circuit, enter Indicates whether RIP is Enabled or Disabled Showing IP Interfaces# show ip interfaces Configuring RIP for an IP Interface Enabling RIP on an IP InterfaceTo stop running the RIP on the interface, enter Configuring a RIP Default Route Configuring a RIP Receive VersionConfiguring RIP Send Version Showing RIP Configurations for IP Addresses Configuring RIP Packet Logging # show rip globals 12describes the fields in the show rip command output # show rip statistics Configuring the Switched Port Analyzer Feature Example of Span Connectivity Configuring Span on a CSS Verifying the Span Configuration on a CSS Config# setspan srcport 3/3 destport 3/12 copyBothConfig# no setspan srcport 3/3 destport 3/12 Field Description Configuring Spanning-Tree Bridging for the CSS CSS Spanning-Tree Bridging Quick Start Config# bridge aging-timeConfig# bridge forward-time Config# bridge hello-time Recommended Display bridge forwarding information Configuring Spanning-Tree Bridge Aging-TimeTo restore the default aging time of 300, enter Set the bridge spanning-tree maximum age, in seconds To restore the default hello time interval of 1, enter Configuring Spanning-Tree Bridge Hello-TimeConfiguring Spanning-Tree Bridge Max-Age To restore the default delay time of 4, enter To set the bridge maximum age to 21, enter Configuring Spanning-Tree Bridge PriorityTo restore the default maximum age of 6, enter Disabling Bridge Spanning-Tree Config# bridge spanning-tree disable Showing Bridge ConfigurationsTo disable spanning-tree bridging, enter To reenable spanning-tree bridging, enter Field Description OL-4580-01 Configuring Open Shortest Path First Ospf Ospf Routing Hierarchy Link-State Databases Ospf Overview Boundry Router2 Ospf Routing Hierarchy Autonomous System AreasBackbone Area Area Border Routers Stub AreaAutonomous System Boundary Routers Link-State Databases Global Ospf Configuration Quick Start CSS Ospf Configuration Quick Start Enable Ospf on the CSS Ospf IP Interface Configuration Quick Start Access global configuration mode. EnterConfig# circuit VLAN6 Configure the IP interface as an Ospf interface. Enter # show ospf advertise Verifying Your Configuration# show ospf global # show ospf redistribute Config# ospf router-id Configuring Ospf on the CSSConfiguring the Ospf Router ID To delete the router ID on the CSS, disable Ospf and enter Configuring an Area To disable OSPF, enterEnabling Ospf Configuring Equal-Cost Routes Configuring Summarized Routes at an ABRRemoving an Area To remove the CSS as an AS boundary router, enter To remove the range, enter Advertising a Route as an Ospf ASE Route VIP is Config# ospf advertise 192.168.44.0 Preceded by an exclamation point Config# no ospf advertise Config# ospf default Advertising a Default ASE Route Advertising Other Routes Through Ospf Config# ospf default metric 10 type1Config# no ospf default Config# ospf redistribute firewall To stop advertising the RIP routes via OSPF, enter Configuring Ospf on a CSS IP InterfaceConfig# ospf redistribute rip metric 3 type1 Config# no ospf redistribute rip Configure this circuit as an Ospf circuit. Enter Configuring the CSS IP Interface as an Ospf Interface Assigning an Ospf Area to the Interface Configuring the Interface AttributesTo reset the interface to the default backbone area, enter To disable Ospf on the interface, enter Setting the Cost Setting the Dead Router IntervalSetting the Hello Packet Interval Setting the Password Setting the Poll IntervalTo remove the Ospf password from the interface, enter Setting the Priority of the CSS Setting the Retransmission IntervalFor example, to set the poll interval to 200 seconds, enter Setting the Transit-Link Delay Showing Ospf InformationTo set the retransmission interval to 10 seconds, enter To show information about Ospf areas, enter 3describes the fields in the show ospf areas command outputShowing Ospf Area Information Showing Global Statistics To show Ospf interfaces, enter Showing IP Interface Information Field Field Description Showing Link-State Databases 6describes the fields in the show ospf lsdb command output To show the entire database, enter# show ospf lsdb Field Description # show ospf ase 7describes the fields in the show ospf ase command outputShowing ASE Entries To show AS-external ASE entries in the LSDB, enter Showing the Configured Advertised ASE Routes To show the configuration of ASE routes into OSPF, enter# show ospf advertise 192.168.11.1/24 Firewall Field Description Showing the Redistribution Policy To show the Ospf neighbors, enter Showing Summary Route Configuration InformationTo show the summary-route configuration information, enter Showing Ospf Neighbors 11 Field Descriptions for show ospf neighbors Command Field Description Field Description Ospf Configuration in a Startup-Configuration File OL-4580-01 Protocol Configuring the Address Resolution ARP Configuration Quick Start Set the time, in seconds, to wait for an ARP resolutionDefine a static ARP mapping Config# no arp Configuring ARP Mapping Config# no arp timeout Configuring ARP TimeoutConfiguring ARP Wait To restore the default wait time of 5 seconds, enter Updating ARP Parameters Clearing ARP Parameters# clear arp cache Showing ARP Information Show arp configfilemanagement-portsummaryiporhost # show arp summary 2describes the fields in the show arp command output # show arp file To display the global ARP configuration, enter4describes the fields in the show arp config command output # show arp config To display the resolution for a host IP address, enter OL-4580-01 Configuring Routing Information Protocol Config# rip redistribute static RIP Configuration Quick StartConfigure the CSS to advertise a route through RIP Config# rip advertise 192.168.1.0/24 Configuring RIP Advertise Configuring RIP RedistributeConfig# no rip advertise 192.168.1.0/24 Config# no rip equal-cost Configuring Equal-Cost RIP Routes Showing RIP Configurations 3describes the fields in the show rip globals command output Field Descriptions for the show rip statistics Command OL-4580-01 Configuring the Internet Protocol IP Configuration Quick Start Configuring an IP Route Configuring the Internet Protocol Configuring an IP Route For example, to configure a blackhole route, enter To remove a static route, enterTo remove a firewall route, enter Disabling an Implicit Service for the Static Route Next Hop To reset the default setting, enterConfig# no ip no-implicit-service Config# no ip source-route Configuring an IP Source RouteConfiguring the IP Record Route Config# ip source-route Syntax for this global configuration command is Configuring Box-to-Box RedundancyConfiguring IP Equal-Cost Multipath To disable box-to-box redundancy, enter Config# no ip subnet-broadcast Config# ip ecmp no-prefer-ingressConfig# no ip ecmp no-prefer-ingress Config# ip ecmp roundrobin Config# no ip uncond-bridging Configuring IP Unconditional BridgingTo restore the default behavior of the CSS, enter Config# ip uncond-bridging Example of Opportunistic Layer 3 Forwarding Config# ip route 0.0.0.0 /0 192.168.1.7 originated-packets Showing IP Configuration InformationConfig# ip opportunistic all Config# no ip opportunistic Showing IP Global Configuration Parameters Whether RIP is enabled or disabled Showing IP Routing Information 4describes the fields in the show ip routes command output Showing IP Statistics Index value that identifies the local interface throughWhich the next hop of this route should be reached TCP Statistics Icmp Statistics ARP Statistics Showing a Summary of IP Global Statistics Resetting IP Statistics Field Description OL-4580-01 Configuring the Cisco Discovery Protocol Recommended Display and verify CDP information for the CSS CDP Configuration Quick StartConfig# cdp holdTime Config# cdp timer Enabling CDP Setting the CDP Hold TimeTo disable CDP transmissions on the CSS, enter Config# no cdp holdTime Setting the CDP Transmission Rate Config# no cdp timerShowing CDP Information Configuring the Dhcp Relay Agent Dhcp Relay Agent Configuration Quick Start Enable the Dhcp relay agent on the CSS circuitOptional Verify the Dhcp configuration Enabling and Disabling Dhcp on the Circuit To disable the Dhcp relay agent on the circuit, enterConfig-circuitVLAN2#no dhcp relay-to Adding a Dhcp Destination on a Circuit # show dhcp-relay-agent global Displaying the Dhcp Relay ConfigurationConfig# no dhcp-agent max-hops Defining the Hops Field Value for Forwarding Dhcp Messages Field Description OL-4580-01 Aging time, configuring for bridging Bpdu guard Displaying information EnablingIN-1 IN-2 CLI IN-3 DNS IN-4 IP Ecmp IN-5 IN-6 IN-7 Switched port analyzer. See also Span MIB-II interface Ospf globalIN-8 IN-9 Symbol overview Zero, resetting Ethernet statistics to IN-10