This chapter provides an overview of the Cisco Broadband Operating System (CBOS) and its features. CBOS is the common operating system for all Cisco Customer Premise Equipment (CPE), including the Cisco 675, the Cisco 675e, the Cisco 676, and the Cisco 677.
Note These products are referred to as the Cisco 67x product line. When you see 67x in this documentation, substitute the hardware product you are using.
The CBOS is modeled after the Cisco Internetworking Operating System (IOS) and features a similar command syntax and format.
This section describes the CBOS-supported features that are common to the Cisco Customer Premise Equipment (CPE) product line.
Reduces or eliminates the need for you to manually configure CPE devices
Minimizes the need for configuration of the PCs in a Small Office/Home Office (SOHO) network
Incorporates the DHCP server and NAT functionality.
DHCP automatically configures the IP addresses of both the Cisco CPE 67x series products and PC clients within the SOHO network. NAT uses one or more public IP address to translate the SOHO network's private IP address space into real, Internet-valid network IP addresses (Figure 1-1).
The combination of DHCP and NAT in the Cisco PPP/ATM environment supports a configurationless CPE provisioning by automatically configuring both the Cisco 67x and the associated SOHO network at power-on. A minimal configuration is required in the user PC (typically a single check-box to enable DHCP operation) but all PCs within the network have identical settings which simplifies initial provisioning and network support.
3. The Cisco 67x obtains configuration information from the service provider's DHCP server.
4. The Cisco 67x turns into a DHCP server and can configure SOHO clients (PC#1, PC#2, and PC#3).
Note If you use the DHCP client mode, you must also use the DHCP server mode.
5. When the DHCP server is enabled, the Cisco 67x must contain a valid DHCP configuration, which has been either manually provisioned or obtained during a previous client transaction.
If this is the first time the Cisco 67x has performed a client request, it ignores all network traffic until the Cisco 67x client transaction has completed.
6. The Cisco 67x saves the client configuration information obtained during the client transaction to NVRAM for subsequent use.
If a client transaction results in configuration information that differs from that which is stored in NVRAM, the Cisco 67x saves the new configuration to NVRAM and uses the new information on the subsequent power-cycle.
NAT in the Cisco 67x translates private (or Internet-invalid) IP addresses to public (Internet-valid) IP addresses. By dynamically creating a table of translation information each time data is exchanged with any network outside of the SOHO network, the CPE device allows multiple PCs to oversubscribe a single, public IP address. This powerful feature both conserves IP addresses and minimizes customer reconfiguration of a local SOHO network.
Use NAT if you cannot use a network's internal private addresses outside either for security reasons or because the addresses are invalid outside the network.
Basic NAT allows a one-to-one mapping between one private address and one public address.
When both NAT and DHCP are enabled, the Cisco 67x becomes virtually configurationless. NAT obtains the public address used for translation in the same manner as described above. However, DHCP does not require any additional provisioning since NAT translates all address information to the outside, public address. You can use a DHCP client transaction to obtain DNS, WINS, and other information for subsequent SOHO DHCP server operation, but this is not required.
When a DHCP client transaction is in progress, the Cisco 67x delays NAT implementation until the client transaction completes. This ensures that the most current information is used for server operation.
The end result for the SOHO users (PC#1, PC#2, and PC#3) (see Figure 1-1) is as follows:
1. SOHO users turn on their un-configured machines with DHCP enabled. Within seconds, they are surfing the Internet using a configuration totally and transparently supplied by their service provider.
2. Clients are not affected by changes at the service provider.
From the CBOS prompt, use the help command to display the online help system for a specified command. Refer to "Using the Command Line Interface," for more information on the help command. To access the Help Facility, enter the following command from the command line:
help [command-name]
or
? [command-name]
For example, to display information about the show version command, enter:
