|
|
Cisco 700 series routers can perform the role of the relay agent, relaying IP configuration information request packets from the LAN interface, over the ISDN interface, to a specified Dynamic Host Configuration Protocol (DHCP) server. Cisco 700 series routers provide DHCP relay, DHCP server, Port Address Translation (PAT), and Internet Protocol Control Protocol (IPCP). This appendix provides descriptions, application notes, and example configurations.
This appendix contains the following sections:
DHCP is a client-server protocol that allows devices on an IP network (the DHCP clients) to request configuration information from a DHCP server. DHCP allocates network addresses from a central pool on an as-needed basis. DHCP is useful for assigning IP addresses to hosts connected to the network temporarily, or for sharing a limited pool of IP addresses among a group of hosts that do not need permanent IP addresses.
DHCP allows for increased automation and fewer network administration problems by:
The following are application notes for DHCP server:
The following are application notes for DHCP relay:
Cisco 700 series routers provide PAT, enabling local hosts on a private IP network to communicate externally.
Packets destined for an external address have their private IP address plus port number translated to the router's external IP address before the IP packet is forwarded to the WAN. IP packets returning to the router have their external IP addresses (plus port number) translated back to the private IP addresses and the packets are forwarded to the LAN.
When PAT is enabled, the transmission of RIP packets is automatically disabled to prevent a broadcast of the private IP addresses externally.
A configuration where PAT is on and DHCP relay is enabled is not valid. DHCP relay will attempt to cross from a public to a private domain. PAT prevents access to the private domain. DHCP relay fails because it must reference the router's private address.
If you are using IP routing, Cisco 700 series routers must be configured for IPCP to connect to routers running Cisco IOS software. Use the set ip framing command in profile mode to enable IPCP for user-defined WAN profiles by setting IP framing to none.
The following example illustrates IPCP enabled by disabling IP framing:
766:2503> set ip framing none
The following are application notes for IPCP address negotiation:
This section describes how to configure a remote Cisco 700 series router for PPP IPCP negotiation to a central site router, such as a Cisco 4500 series router, running Cisco IOS software.
Figure C-1 is an illustration of the configuration used in this example.
Following are the commands for configuring the remote Cisco 765 series router for point-to-point IPCP negotiation with a Cisco 4500 router:
set system 765 set user 4500 set active set 1 number phone_number set 2 number phone_number set ip routing on set ip rip version 2 set ip rip receive v2 set ip rip update linkup reboot
Following are the commands for configuring the Cisco 4500 series router for all examples contained in this chapter:
configure terminal hostname 4500 username 765 isdn switch-type primary-5ess interface Ethernet0 ip address 172.168.100.1 255.255.255.0 interface Serial0 shutdown no fair-queue interface BRI0 ip unnumbered Ethernet0 ip rip send version 2 ip rip receive version 2 no ip mroute-cache encapsulation ppp peer default ip address pool test dialer idle-timeout 3600 dialer map ip 0.0.0.0 name IOS700 broadcast dialer-group 1 no fair-queue compress stac ppp multilink router rip network 172.168.100.0 network 172.168.99.0 network 172.168.101.0 ip local pool test 172.168.99.1 no ip classless dialer-list 1 protocol ip permit line con 0 line aux 0 line vty 0 4 login end
For details regarding the commands listed here, see the related chapter in this publication.
You can use the show ip configuration all and show ip route all commands to see the IPCP negotiation address:
765:4500> show ip configuration all
Profile Routing Frame IP Address Netmask RIP TX RX Prop Cost
------------------------------------------------------------------------
Internal ON ETH2 172.168.99.1 255.255.255.0 V1 PER V1 ON 1
4500 ON IPCP 0.0.0.0 0.0.0.0 V2 LIN V2 ON 1
Profile PAT Multicast Summarization Netbios Spoofing/Left(min)
--------------------------------------------------------------------
Internal OFF OFF OFF OFF /0
4500 OFF OFF OFF OFF /0
765:4500> show ip route all
Profile Type Destination Bits Gateway Prop Cost Source Age
------------------------------------------------------------------------
4500 NET 172.168.100.0 24 172.168.100.1 ON 2 RIP 7
Internal NET 192.168.99.0 24 DIRECT ON 1 IPCP 0
This section describes how to configure a remote Cisco 700 series router for DHCP relay with IPCP negotiation to a central site router running Cisco IOS software.
Figure C-2 is an illustration of the configuration used in this example.
set system 765 set user 4500 set 1 number phone_number set 2 number phone_number set ip routing on set ip rip version 2 set ip rip receive v2 set ip rip update linkup set dhcp relay 172.168.100.2 reboot
You can use the show ip configuration and show ip route commands to see the IPCP negotiation address:
765> show ip configuration all Profile Routing Frame IP Address Netmask RIP TX RX Prop Cost ------------------------------------------------------------------------ Internal ON ETH2 172.168.99.1 255.255.255.0 V1 PER V1 ON 1 4500 ON IPCP 0.0.0.0 0.0.0.0 V2 LIN V2 ON 1 Profile PAT Multicast Summarization Netbios Spoofing/Left(min) -------------------------------------------------------------------- Internal OFF OFF OFF OFF /0 4500 OFF OFF OFF OFF /0 765> show ip route all Profile Type Destination Bits Gateway Prop Cost Source Age ------------------------------------------------------------------------ 4500 NET 172.168.100.0 24 172.168.100.1 ON 2 RIP 0 Internal NET 172.168.99.0 24 DIRECT ON 1 IPCP 0
Enter the show dhcp configuration command to see the IP address returned by DHCP:
765> show dhcp configuration Environment DHCP Server OFF DHCP Relay 172.168.100.2 IP Address Pool NONE Subnet Mask NONE DNS Configuration Primary DNS Server NONE Secondary DNS Server NONE Domain "" Gateways Primary Gateway NONE Secondary Gateway NONE WINS Configuration Primary WINS Server NONE Secondary WINS Server NONE Address In Use IP Address Mac Address 0 IP addresses allocated, 0 free
This section describes how to configure a remote Cisco 700 series router for DHCP server with IPCP negotiation to a central site router running Cisco IOS software.
Figure C-3 is an illustration of the configuration used in this example.
Following are the commands for configuring the remote Cisco 765 series router as a DHCP server with IPCP negotiation with a Cisco 4500 router:
set system 765 set dhcp server set user 4500 set active set 1 number phone_number set 2 number phone_number set ip routing on set ip rip version 2 set ip rip receive v2 set ip rip update periodic reboot
When a call is made, you can use the show ip configuration all and show ip route all commands to see the IPCP negotiation address:
765> show ip configuration all Profile Routing Frame IP Address Netmask RIP TX RX Prop Cost ------------------------------------------------------------------------ LAN ON ETH2 10.0.0.1 255.0.0.0 V1 OFF V1 ON 1 Internal ON ETH2 172.168.99.1 255.255.255.0 V1 PER V1 ON 1 4500 ON IPCP 0.0.0.0 0.0.0.0 V2 LIN V2 ON 1 Profile PAT Multicast Summarization Netbios Spoofing/Left(min) -------------------------------------------------------------------- LAN OFF OFF OFF OFF /0 Internal OFF OFF OFF OFF /0 4500 OFF OFF OFF OFF /0 IOS700> show ip route all Profile Type Destination Bits Gateway Prop Cost Source Age ------------------------------------------------------------------------ 4500 NET 172.168.100.0 24 172.168.100.1 ON 2 RIP 20 Internal NET 172.168.99.0 24 DIRECT ON 1 IPCP 0 LAN NET 10.0.0.0 8 DIRECT ON 1 DIRECT 0
Enter the show dhcp configuration command to see the IP address returned by DHCP:
765> show dhcp configuration
This section describes how to configure a remote Cisco 700 series router for PAT with IPCP single-destination negotiation to a central site router running Cisco IOS software.
Figure C-4 is an illustration of the configuration used in this example.
Following are the commands for configuring the remote Cisco 765 series router for PAT with IPCP single-destination negotiation with a Cisco 4500 router:
set system 765 set user 4500 set active set 1 number phone_number set 2 number phone_number set ip routing on set ip rip version 2 set ip rip receive v2 set ip pat on set ip pat po ftp 10.0.0.2 reboot
When a demand call is made, you can use the show ip config all and show ip route all commands to see the IPCP negotiation address:
765> show ip configuration all Profile Routing Frame IP Address Netmask RIP TX RX Prop Cost ------------------------------------------------------------------------ LAN ON ETH2 10.0.0.1 255.0.0.0 V1 OFF V1 ON 1 Internal ON ETH2 172.168.99.1 255.255.255.0 V1 PER V1 ON 1 4500 ON IPCP 0.0.0.0 0.0.0.0 V2 OFF V2 ON 1 Profile PAT Multicast Summarization Netbios Spoofing/Left(min) -------------------------------------------------------------------- LAN OFF OFF OFF OFF /0 Internal OFF OFF OFF OFF /0 4500 OFF OFF OFF OFF /0 765:4500> show ip route all Profile Type Destination Bits Gateway Prop Cost Source Age ------------------------------------------------------------------------ 4500 NET 172.168.100.0 24 172.168.100.1 ON 2 RIP 4 Interna NET 172.168.99.0 24 DIRECT ON 1 IPCP 0 LAN NET 10.0.0.0 8 DIRECT ON 1 DIRECT 0
Enter the show ip pat command to see the services returned by PAT:
765:4500> show ip pat Dropped - icmp 0, udp 0, tcp 0, map 0, frag 0 Timeout - udp 5 minutes, tcp 30 minutes Port handlers [no default]: Port Handler Service ------------------------------------- 21 10.0.0.2 FTP 23 Router TELNET 67 Router DHCP Server 68 Router DHCP Client 69 Router TFTP 80 Router HTTP 161 Router SNMP 162 Router SNMP-TRAP 520 Router RIP
This section describes how to configure a remote Cisco 700 series router for DHCP server with PAT and IPCP single-destination negotiation to a Cisco 4500 series router running Cisco IOS software at a central site.
Figure C-5 is an illustration of the configuration used in this example.
Following are the commands for configuring the remote Cisco 765 series router for PAT with IPCP single-destination negotiation with a Cisco 4500 router:
set system 765 set user 4500 set active set 1 number phone_number set 2 number phone_number set ip routing on set ip rip version 2 set ip rip receive v2 set ip pat on set ip pat po ftp 10.0.0.2 reboot
When a demand call is made, you can use the show ip config all and show ip route all commands to see the IPCP negotiation address.
This section describes how to configure a remote Cisco 700 series router for DHCP server with PAT and IPCP dual-destination PPP negotiation to two routers running Cisco IOS software.
Figure C-6 is an illustration of the configuration used in this example.
Following are the commands for configuring the remote Cisco 765 series router as a DHCP server with PAT and IPCP multilink PPP to two routers running Cisco IOS software:
set system 765 set ip routing on set ip rip version 2 set ip rip receive v2 set ip rip update periodic set multidestination on set ip pat po ftp 172.168.99.3 cd internal set ip address 172.168.99.1 set dhcp server cd set user 4500 set active 4500 set 1 number phone_number set 2 number phone_number set pat on set user 2500 set active set 1 number phone_number set 2 number phone_number set pat on reboot
When a demand call is made, you can use the show ip configuration all command to see the IPCP negotiation address:
765:2500> show ip configuration all Profile Routing Frame IP Address Netmask RIP TX RX Prop Cost ------------------------------------------------------------------------ Internal ON ETH2 172.168.99.1 255.255.255.0 V1 OFF V1 ON 1 4500 ON IPCP 172.168.103.1 255.255.255.0 V2 PER V2 ON 1 2500 ON IPCP 172.167.1.1 255.255.255.0 V2 PER V2 ON 1 Profile PAT Multicast Summarization NetBIOS Spoofing/Left(min) -------------------------------------------------------------------- LAN OFF OFF OFF OFF /0 4500 OFF OFF OFF OFF /0 2500 OFF OFF OFF OFF /0
Enter the show dhcp connections command to see the IP addresses returned by DHCP:
765:4500> show dhcp connections Environment DHCP Server ON DHCP Relay OFF IP Address Pool Start IP Address 172.168.99.2 Count 128 Subnet Mask 255.255.255.0 DNS Configuration Primary DNS Server NONE Secondary DNS Server NONE Domain "" Gateways Primary Gateway 172.168.99.1 Secondary Gateway NONE WINS Configuration Primary WINS Server NONE Secondary WINS Server NONE Address In Use IP Address Mac Address <Q> and <enter> to Quit or <enter> for MORE 172.168.99.2 0000c0e96571 172.168.99.3 00a0244196b7 2 IP addresses allocated, 126 free
|
|