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This chapter describes how to configure the Cisco uBR910 series cable data service unit (DSU) for features beyond those supported in the default operation mode of "plug and play" DOCSIS bridging. This chapter describes the following configurations:
Depending on the Cisco IOS software image being used and the feature sets it supports, these configurations could be combined.
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Tips Use the commands shown in this chapter to set up a typical Cisco uBR910 series DSU for the desired feature. Then save the configuration into a file that can be downloaded to the Cisco uBR910 series during power-on or reset. |
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Caution Incorrectly configuring the Cisco uBR910 series DSU can cause loss of network connectivity. Before attempting to reconfigure a unit, print the last working configuration, and ensure remote configuration is enabled for the site. If the Cisco uBR910 series does not connect to the network after you have reconfigured it, enter the cable downstream saved frequency from the printout, and then clear the interface. Power off and then power on the system. If powering off the unit does not correct the problem after a few minutes, give the write erase and copy startup-config running-config commands; then enter the correct saved frequency. If network connectivity is not restored, contact your network management, provisioning, or billing system administrator to reload the software applicable to your network. |
The Cisco uBR910 series DSU must be configured for routing mode to use advanced features such as the DHCP server. The following steps are required to configure the routing mode on the Cisco uBR910 series DSU:
To configure the Cisco uBR910 series DSU, log in to the unit, enter global configuration mode, and enter the commands shown in the following table:
| Command | Purpose | |||
|---|---|---|---|---|
Step 1 | uBR910(config)# int c 0 | Enter interface configuration mode for the cable interface. | ||
Step 2 | uBR910(config-if)# ip address dhcp | Configure the cable interface so it obtains its IP address from a DHCP server during the power-on provisioning process. | ||
Step 3 | uBR910(config-if)# no cable-modem compliant bridge | Disable DOCSIS-compliant bridging. | ||
Step 4 | uBR910(config-if)# bridge-group bridge-group | Assign the interface to a bridge group (1 to 63) for integrated routing and bridging across the cable and serial interfaces. | ||
Step 5 | uBR910(config-if)# no ip directed-broadcast | Disable the forwarding of directed-broadcasts on the cable interface. | ||
Step 6 | uBR910(config-if)# exit | Return to global configuration mode. | ||
Step 7 | uBR910(config)# int s 0 | Enter interface configuration mode for the serial interface. | ||
Step 8 | uBR910(config-if)# description string | (Optional) Enter an arbitrary description up to 80 characters for this interface. | ||
Step 9 | uBR910(config-if)# ip unnumbered cable-modem0 | Use the cable interface's IP address---which is assigned by the DOCSIS DHCP server---for the serial interface to conserve IP addresses. (Alternatively, you can also use the ip address command to assign a static IP address to the serial interface.) | ||
Step 10 | uBR910(config-if)# bridge-group bridge-group | Assign the serial interface to the same bridge spanning group for the cable interface. | ||
Step 11 | uBR910(config-if)# no ip directed-broadcast | Disable the forwarding of directed-broadcasts on the serial interface. | ||
Step 12 | uBR910(config-if)# encapsulation serial-protocol | Specify the serial protocol to be used on this link: ppp or hdlc. | ||
Step 13 | uBR910(config-if)# no keepalive | Disable keepalive messages sent to the interface by the Cisco IOS software. | ||
Step 14 | uBR910(config-if)# clockrate bps | Enter the clock rate in bits per second (bps)---the possible values are in the range from 300 to 8000000 bps, but you must enter a speed supported by the serial interfaces being used on the Cisco uBR910 series DSU and the access router. | ||
Step 15 | uBR910(config-if)# bandwidth kilobits-per-second | Enter the bandwidth in kilobits per second (Kbps)---this is optional but recommended because the Cisco IOS software uses this value when calculating routing metrics.
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Step 16 | uBR910(config-if)# exit | Exit the interface configuration mode for the serial interface. | ||
Step 17 | uBR910(config)# ip routing | Enable IP routing. | ||
Step 18 | To use RIPv2: uBR910(config)#router rip uBR910(config-router)# version 2 uBR910(config-router)# network cable-network-number uBR910(config-router)# network other-network-number uBR910(config-router)# exit | (Optional) Enter router configuration mode. Enable RIP version 2 routing. Enable routing on the cable interface's IP network. Enable routing on other attached IP networks. Return to global configuration mode. | ||
Step 19 | To use static routes: uBR910(config)# ip route prefix mask {address | interface} [distance] [tag tag] [permanent] | (Optional) Specify one or more static routes. | ||
Step 20 | uBR910(config)# ip route 0.0.0.0 0.0.0.0 ip-address | (Optional) Specify a default route so that all packets without an established route are forwarded to the default gateway (ip-address should be the IP address for the CMTS), regardless of the routing metrics. | ||
Step 21 | uBR910(config)# no cdp run | Disable the Cisco Discovery Protocol (CDP) on the Cisco uBR910 series DSU. (CDP is a proprietary protocol for the discovery of Cisco routers running protocols other than TCP/IP; because DOCSIS cable data networks are TCP/IP networks, CDP is not necessary on the Cisco uBR910 series DSU.) | ||
Step 22 | uBR910(config)# bridge bridge-group protocol ieee | Enable the IEEE 802.1D Spanning-Tree Protocol for the bridge group that joins the serial and cable interfaces. | ||
Step 23 | uBR910(config)# ip default-gateway ip-address | Set the default gateway for routing (typically, this is the CMTS). | ||
Step 24 | uBR910(config)# ip classless | (Optional) Enable the forwarding of packets that are destined for unrecognized subnets to the best supernet route. | ||
Step 25 | uBR910# copy running-config startup-config Building configuration... | Save the configuration to nonvolatile memory so that it will not be lost in the event of a reset, power cycle, or power outage. | ||
Step 26 | uBR910# show startup-config | Display the configuration file that was just created. |
To verify that routing is enabled, enter the show startup-config command. The following example shows a sample configuration file for basic routing mode; the relevant commands are shown in bold.
Version 12.1 no service pad service timestamps debug uptime service timestamps log uptime no service password-encryption service internal ! hostname ubr910 ! enable password lab ! ! clock timezone - -5 ip subnet-zero ! ! interface Serial0 description ...to access router: route IP, bridge all others bandwidth 8000 ip unnumbered cable-modem0 no ip directed-broadcast load-interval 30 no keepalive fair-queue 64 256 0 clockrate 8000000 bridge-group 1 ! interface cable-modem0 ! This example assumes the cable interface obtains ! an IP address in the 10.1.4.0 subnet ip address dhcp no ip directed-broadcast load-interval 30 no cable-modem compliant bridge bridge-group 1 ! router rip version 2 network 10.0.0.0 no auto-summary ! ! This example assumes the CMTS has the IP address 10.1.4.1 ip default-gateway 10.1.4.1 ip classless ip route 0.0.0.0 0.0.0.0 10.1.4.1 no ip http server ! no cdp run bridge 1 protocol ieee ! line con 0 exec-timeout 0 0 transport input none line vty 3 4 no login ! end
When in routing mode, the Cisco uBR910 series DSU can act as a DHCP server for the CPE devices it is connecting to the cable network. A service provider then does not have to supply IP addresses to all of the PCs at a subscriber's site; instead, the provider supplies a pool of IP addresses the Cisco uBR910 series DSU then allocates to the PCs as needed.
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Note The Cisco uBR910 series DSU must be configured for routing mode to act as a DHCP server. If in bridging mode, you can configure the Cisco uBR910 series to proxy DHCP client requests to the DHCP server at the headend by giving the cable helper-address dhcp-server-ip-address host interface configuration command. (The ip helper-address and ip forward-protocol interface configuration commands can also be used for this purpose.) |
To configure the Cisco uBR910 series DSU to act as a DHCP server, log in to the unit, enter global configuration mode, and enter the commands shown in the following table:
| Command | Purpose | |
|---|---|---|
Step 1 | uBR910(config)# ip dhcp pool pool-name | Create an address pool for the DHCP server named pool-name and enter DHCP configuration mode. |
Step 2 | uBR910(config-dhcp)# network IP-network-number subnet-mask | Specify the network number and subnet mask for the IP address pool. These IP addresses should be part of the subnet provided by the CMTS cable interface. For example, network 10.17.91.0 255.255.255.0 reserves the IP addresses 10.17.91.1 to 10.17.91.254 for CPE devices. |
Step 3 | uBR910(config-dhcp)# domain-name domain-name | The domain name that should be assigned to CPE devices (for example, cisco.com). |
Step 4 | uBR910(config-dhcp)# dns-server ip-address | The IP address for the DNS server provided by the service provider that will service the DNS requests from the CPE devices. More than one DNS server can be specified. |
Step 5 | uBR910(config-dhcp)# default-router ip-address | The IP address for the default router for the CPE devices (typically, this is the CMTS). More than one default router can be specified. |
Step 6 | uBR910(config-dhcp)# exit | Return to global configuration mode. |
Step 7 | uBR910# show startup-config | Display the configuration file that was just created. |
To verify that the DHCP server is enabled, enter the show startup-config command. A sample configuration file for a Cisco uBR910 series DSU acting as a DHCP server is shown below. The relevant commands are shown in bold.
Version 12.1 no service pad service timestamps debug uptime service timestamps log uptime no service password-encryption service internal ! hostname ubr910 ! enable password lab ! ! clock timezone - -5 ip subnet-zero ! ! ip dhcp pool Clients network 10.1.1.0 255.255.255.0 domain-name cisco.com dns-server 10.1.43.17 default-router 10.1.4.1 ! ! interface Serial0 description ...to access router: route IP, bridge all others bandwidth 8000 ip unnumbered cable-modem0 no ip directed-broadcast load-interval 30 no keepalive fair-queue 64 256 0 clockrate 8000000 bridge-group 1 ! ! This example assumes the cable interface obtains ! an IP address in the 10.1.4.0 subnet interface cable-modem0 ip address dhcp no ip directed-broadcast load-interval 30 no cable-modem compliant bridge bridge-group 1 ! router rip version 2 network 10.0.0.0 no auto-summary ! ! This example assumes the CMTS has the IP address 10.1.4.1 ip default-gateway 10.1.4.1 ip classless ip route 0.0.0.0 0.0.0.0 10.1.4.1 no ip http server ! no cdp run bridge 1 protocol ieee ! line con 0 exec-timeout 0 0 transport input none line vty 3 4 no login ! end
When using a Cisco IOS image that supports the Easy IP feature, the Cisco uBR910 series DSU supports Network Address Translation (NAT) and Port Address Translation (PAT). This allows multiple computers connected to the Cisco uBR910 series DSU to use the same IP address when communicating through the cable interface to the Internet or other public networks.
On the Cisco uBR910 series DSU, the "inside" network is the private network connected through the serial interface, and the "outside" network is the network accessed through the cable network (such as the Internet or a company Intranet). The inside addresses are translated to an external IP address that is valid in the outside network. One IP address can be used for multiple computers because a unique port address is used to identify individual computers on the private network.
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Note NAT/PAT can be used in either DOCSIS-bridging or routing mode. |
The following table shows the applicable commands:
| Command | Purpose | |
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Step 1 | uBR910(config)# ip nat inside source list list-id interface cable-modem0 overload or uBR910(config)# ip nat pool pool-name start-ip end-ip {netmask netmask | prefix-length prefix-length} uBR910(config)# ip nat inside source list list-id pool pool-name overload | Enable translation of the inside source addresses---the "inside" addresses are translated before being presented to the "outside" network. The list-id specifies an access-list that defines the IP addresses that will be used, and overload specifies that multiple inside IP addresses can use the same outside IP address (but different port numbers uniquely identify each inside host). Use the interface cable-modem0 form of the ip nat inside command to specify that address negotiation should occur with traffic sent over the cable network. To specify a pool of IP addresses to be used for NAT translation, use the ip nat pool command to create the pool of IP addresses to be used. Then use the pool version of the ip nat inside command. |
Step 2 | uBR910(config)# int s 0 | Enter interface configuration mode for the serial interface. |
Step 3 | uBR910(config-if)# ip nat inside | Specify that the serial interface is the "inside" of the NAT/PAT translation. |
Step 4 | uBR910(config-if)# exit | Exit interface configuration mode. |
Step 5 | uBR910(config)# interface cable-modem0 | Enter interface configuration mode for the cable interface. |
Step 6 | uBR910(config-if)# ip nat outside | Specify that the cable interface is the "outside" of the NAT/PAT translation. |
Step 7 | uBR910(config-if)# exit | Exit interface configuration mode. |
Step 8 | uBR910(config)# access-list list-id permit any | Create the access list specified by the list-id parameter in the ip nat inside source command. (This particular example specifies that all IP addresses should be accepted; the filter can be as complex as needed to include or exclude any combination of IP addresses.) |
Step 9 | uBR910# copy running-config startup-config Building configuration... | Save the configuration to nonvolatile memory so that it will not be lost in the event of a reset, power cycle, or power outage. |
Step 10 | uBR910# show startup-config | Display the configuration file that was just created. |
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Note Additional options, such as static IP address translation, are possible when using NAT/PAT. For more information about the Easy IP and NAT/PAT feature set, see the Dial-Related Addressing Services documentation, available on CCO and the Documentation CD-ROM. |
The following configuration shows an example of a Cisco uBR910 series DSU in DOCSIS-bridging mode that performs NAT/PAT translation on all IP addresses connected through the serial interface. The addressing is overloaded so that multiple IP addresses on the internal network can use the same external IP address over the cable interface; different port numbers are used to uniquely identify each device connecting through the serial interface. The relevant commands are shown in bold.
Version 12.1 no service pad service timestamps debug uptime service timestamps log uptime no service password-encryption service internal ! hostname ubr910 ! enable password lab ! ! ip nat inside source list 1 interface cable-modem0 overload clock timezone - -5 ip subnet-zero ! ! interface Serial0 description ...to access router: route IP, bridge all others bandwidth 8000 ip unnumbered cable-modem0 no ip directed-broadcast load-interval 30 ip nat inside no keepalive fair-queue 64 256 0 clockrate 8000000 bridge-group 1 ! ! This example assumes the cable interface obtains ! an IP address in the 10.1.4.0 subnet interface cable-modem0 ip address dhcp no ip directed-broadcast ip nat outside load-interval 30 no cable-modem compliant bridge bridge-group 1 ! router rip version 2 network 10.0.0.0 no auto-summary ! ! This example assumes the CMTS has the IP address 10.1.4.1 ip default-gateway 10.1.4.1 ip classless ip route 0.0.0.0 0.0.0.0 10.1.4.1 access-list 1 permit any no ip http server ! no cdp run bridge 1 protocol ieee ! line con 0 exec-timeout 0 0 transport input none line vty 3 4 no login ! end
Posted: Fri Jul 21 12:31:17 PDT 2000
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