Table Of Contents
Configuring the Cisco uBR900 Series Cable Access Routers
Cisco IOS Software Feature Sets
Downstream and Upstream Data Transfer
Triple Data Encryption Standard
NetRanger Support—IOS Intrusion Detection
Related Features and Technologies
Configuring a Host Name and Password
Verifying the Host Name and Password
Configuration, Verification, and Troubleshooting Tips
Configuring Ethernet and Cable Access Router Interfaces
Verifying IP Address Configuration
Configuration, Verification, and Troubleshooting Tips
Reestablishing DOCSIS-Compliant Bridging
Verifying DOCSIS-Compliant Bridging
Customizing the Cable Access Router Interface
Using Multiple PCs with the Cable Access Router
Basic Internet Access Bridging Configuration
Basic Internet Access Routing Configuration
Multicast-Enabled Routing Configuration
VoIP Bridging Configuration Using H.323v2
VoIP Routing Configuration Using H.323v2
VoIP Bridging Configuration Using SGCP
cable-modem downstream saved channel
cable-modem upstream preamble qpsk
show controllers cable-modem bpkm
show controllers cable-modem des
show controllers cable-modem filters
show controllers cable-modem lookup-table
show controllers cable-modem mac
show controllers cable-modem phy
show controllers cable-modem tuner
Configuring the Cisco uBR900 Series Cable Access Routers
This document addresses the following topics:
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VoIP Bridging Configuration Using SGCP
Feature Overview
Cisco uBR900 series cable access routers are fully-functional Cisco IOS routers and standards-based bidirectional cable modems that give a residential or small office/home office (SOHO) subscriber high-speed Internet or Intranet access and packet telephone services via a shared two-way cable system and IP backbone network. Cisco uBR900 series cable access routers are based on the current Data-Over-Cable Service Interface Specifications (DOCSIS) standards, and interoperate with any bidirectional, DOCSIS-qualified headend cable modem termination system (CMTS).
Cisco uBR900 series routers connect computers, telephone equipment, and other customer premises devices at a subscriber site to the service provider's Hybrid/Fiber Coax (HFC) and IP backbone network. Functioning as cable modems, the Cisco uBR900 series routers transport data and voice traffic on the same cable system that delivers broadcast TV signals.
Cisco uBR900 series cable access routers typically ship from the Cisco factory with a Cisco Internetwork Operating System (IOS) software image stored in nonvolatile memory (NVRAM). The standard Cisco IOS software image supports DOCSIS-compliant bridging operation for data as the default.
Based on the feature licenses purchased, other Cisco IOS images can be downloaded from Cisco Connection Online (CCO). Each Cisco uBR900 series router in your network can then be configured to support Voice over IP (VoIP) and/or other special operating modes based on your service offering and the practices in place for your network. A Cisco uBR900 series device can function as an advanced router, providing wide area network (WAN) data connectivity in a variety of configurations.
Cisco IOS Software Feature Sets
This section briefly describes the common feature sets supported by the Cisco uBR900 series cable access routers. Each feature set contains a number of features that provide a specific functionality such as Voice over IP (VoIP) or virtual private network (VPN) access.
The following feature set categories are currently available:
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The data and voice feature sets add Voice over IP (VoIP) support to the same base features contained in the data only feature sets. Telephones that are connected to the uBR924 cable access router can make voice calls over the Internet using either the H.323 (Gateway/Gatekeeper) voice control protocol or Simple Gateway Control Protocol (SGCP). (For more information on these protocols, refer to H.323 Protocol Stack and SGCP Protocol Stack in this document.)
Because voice calls are real-time traffic, the Cisco uBR924 cable access router supports the DOCSIS Quality of Service (QoS) enhancements to give higher priority to IP packets containing voice traffic.
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The following feature sets are available in data and voice versions as well as in data only versions:
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These feature sets are described in the following sections.
Base IP Bridging
Base IP Bridging includes full and DOCSIS-compliant bridging and DOCSIS Baseline Privacy. The Base IP Bridging feature set allows the Cisco uBR900 series cable access router to function as a DOCSIS 1.0 cable modem and to interoperate with any DOCSIS 1.0-qualified CMTS. It provides basic high-speed Internet connectivity for users who want to connect only one computer to the cable network.
DOCSIS-compliant bridging (also referred to as "plug-and-play" bridging) is the default configuration for Cisco uBR900 series cable access routers. While in plug-and-play bridging mode, the router locates a downstream and upstream channel; finds ToD, TFTP, and DHCP servers; obtains an IP address; downloads a DOCSIS configuration file; and obtains DHCP parameters to work in bridging mode.
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In DOCSIS-compliant bridging mode, the Cisco uBR900 series cable access router acts as a transparent bridge for the following device combinations:
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Home Office (Easy IP)
The Home Office feature set provides high-speed Internet connectivity for customers who have a small home network (typically 2-4 computers). In addition to full DOCSIS 1.0 support and all of the functionality of the Base IP Bridging feature set, the Home Office feature set (also known as Easy IP) supports intelligent Dynamic Host Configuration Protocol (DHCP) server functions, including DHCP Relay Agent and DHCP Client functionality. It also supports Easy IP (NAT/PAT).
This feature set allows the Cisco uBR900 series cable access router great flexibility in administering IP addresses for the PCs and other customer premises equipment it is connecting to the cable network. The DHCP functionality allows intelligent use of the IP addresses that allow customer premises computers and other equipment to connect to the Internet. The NAT/PAT functionality allows you to use private IP addresses on the local network, while still maintaining connectivity to the Internet.
Small Office
In addition to full DOCSIS 1.0 support and all of the functionality of the Easy IP feature set, the Small Office feature set supports the Cisco IOS firewall feature set which provides a wide range of security features for Cisco uBR900 series cable access routers. Using the firewall feature set, Cisco uBR900 series cable access routers act as buffers between the customer's private enterprise network and the Internet and other connected public networks.
In firewall mode, the Cisco uBR900 series cable access router provides a high-speed Internet connection for an office's local network while protecting the computers on the office network from common attacks such as denial of service attacks and destructive Java applets, as well as real-time alerts of such attacks.
The Small Office feature set can be optionally extended with support for IPSec encryption to ensure that the traffic passed over the Internet cannot be intercepted. You can select either standard 56-bit IPSec Network Security encryption or high-security 168-bit Triple Data Encryption Standard (DES) encryption.
Telecommuter
In addition to full DOCSIS 1.0 support and all of the functionality of the Easy IP feature set, the Telecommuter feature set supports IPSec encryption and the Layer 2 Tunneling Protocol (L2TP), which can establish secure high-speed Internet connections between employees' homes and the office local network.
IPSec is an IP security feature that provides robust authentications and encryption of IP packets for the secure transmission of sensitive information over unprotected networks such as the Internet. You can select either standard 56-bit IPSec Network Security encryption or high-security 168-bit Triple Data Encryption Standard (DES) encryption.
L2TP is an extension of the Point-to-Point Protocol (PPP) that allows computers on different physical networks to interoperate as if they were on the same local area network (LAN). These features are important components for Virtual Private Networks (VPNs).
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Data Operations
illustrates a typical broadband data cable system. Data transmitted to a Cisco uBR900 series cable access router from the service provider's CMTS shares a 27 or 26 Mbps, 6 MHz data channel in the 88 to 860 MHz range. The Cisco uBR900 series cable access router shares an upstream data rate of up to 10 Mbps on a 200 kHz-wide to 3.2 MHz-wide channel in the 5 to 42 MHz range.
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Figure 1 Typical Cisco Broadband Data Cable System
Operating Modes
The broadband data cable system uses multiple types of access control to ensure efficient use of bandwidth over a wide range of loading conditions. Advanced queuing techniques and service algorithms are used to define the acquisition and release of channels.
Cisco uBR900 series cable access routers support 64 or 256 Quadrature Amplitude Modulation (QAM) downstream, and Quadrature Phase Shift Keying (QPSK) or 16 QAM upstream transmission. This allows the CMTS system administrator to set the preferred modulation scheme based on the quality of the cable plant.
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The system uses Transmission Control Protocol/Internet Protocol (TCP/IP) to transmit data. TCP/IP transmits data in segments encased in IP datagrams, along with checksums to detect data corruption and sequence numbers to ensure an ordered byte stream on the TCP connection between the Cisco cable access router and the CMTS.
Cisco cable access routers also support multicast services—data streams sent to groups of subscribers. These applications utilize the User Datagram Protocol (UDP) instead of TCP. Since UDP does not mandate upstream acknowledgments, these applications can be very efficient in the network. Additionally, restricting upstream throughput will have no effect on downstream UDP streaming throughput.
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Data Specifications
Service Assignments
Each Cisco uBR900 series cable access router on the network is configured to receive data on a particular downstream channel. A downstream channel contains upstream segment(s). Each upstream segment typically serves more than one fiber node.
Partitioning the upstream plant into smaller segments significantly reduces the number of potential ingress sources and failure points. The CMTS divides the cable plant into downstream channels and upstream segments or clusters of nodes.
Downstream and Upstream Data Transfer
When operating normally, the Cisco uBR900 series cable access router receives data addressed to it from the CMTS. The router reads the address in the header of the message, filters the message and forwards it to the appropriate device at the subscriber site.
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For upstream data transfer, the Cisco cable access router uses a request/grant mechanism to obtain upstream bandwidth. The CMTS configures, via MAC messages, upstream parameters associated with transmissions from all Cisco cable access routers on the system. Service class registration is granted based on class assignment and load provisioning. Upstream channels are time slotted and divided into basic scheduling time units.
The CMTS informs the Cisco cable access router of minislot structures on the upstream channel. Some minislots are marked as contention-based—shared by routers to make bandwidth (timeslot) requests with the CMTS. Others are grouped together into unicast grants for specific routers to send their data bursts. Yet others are grouped together into maintenance slots for "keep alive" messages from routers to the CMTS.
Bridging Applications
In bridging applications, the Cisco uBR900 series cable access router acts as a transparent bridge for up to 254 devices depending on the version of Cisco IOS software you are using. Older versions of software allow a maximum of 3 CPE devices to be bridged. The cable access router is connected to the Internet through the coaxial cable interface. All four 10BaseT Ethernet ports are treated as one Ethernet interface by the Cisco IOS software. The IP addresses for the CPE devices and the coaxial cable interface are typically in the same subnet, although this is not a requirement.
The Cisco uBR900 series complies with the DOCSIS standards for interoperable cable access routers; it supports full transparent bridging as well as DOCSIS-compliant transparent bridging.
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Figure 2 Cisco uBR900 Series Cable Access Router in a Bridging Configuration
DOCSIS-compliant transparent bridging is the factory default configuration of the Cisco uBR900 series cable access router. If your cable service provider is using a DHCP server, all you need to do is connect the cables and power on the cable access router; your service provider's configuration program will automatically configure both the coaxial cable interface and the bridging functionality. You do not need to set up IP addresses for the attached PCs or enter any Command Line Interface (CLI) configuration commands. This type of operation is called plug-and-play bridging.
In DOCSIS-compliant bridging mode, the cable access router is able to locate a downstream and upstream channel; find the TOD, TFTP, and DHCP server(s); obtain an IP address; download a DOCSIS configuration file; and obtain DHCP parameters to work in a bridging mode.
You can configure a customized bridging application on the Cisco uBR900 series using a downloadable configuration file or the CLI. See the sections "Configuring Bridging" on page 41 and "Customizing the Cable Access Router Interface" on page 44 for details.
Routing Applications
The Cisco uBR900 series cable access router can be configured to act as a router to preserve IP address space and limit broadcasts that can impact the performance of the network. A typical use would be if you are connecting the cable access router to an internal Ethernet hub that is connected to an existing PC network. The Cisco uBR900 series supports Routing Information Protocol Version 2 (RIP V2) for this application.
When configured in routing mode, the Cisco uBR900 series is automatically configured to use the headend's IP address as its IP default gateway. This allows the cable access router to send packets not intended for the Ethernet interface to the headend when IP host-routing is configured.
RIP V2 routing is useful for small internetworks in that it enables optimization of Network Interface Center (NIC)-assigned IP addresses by defining variable-length subnet masks (VLSMs) for network addresses, and it allows classless interdomain routing (CIDR) addressing schema.
Figure 3 Cisco uBR900 Series Cable Access Router in a Routing Configuration with a Hub
Layer 2 Tunneling Protocol
Layer 2 Tunneling Protocol (L2TP) is an emerging Internet Engineering Task Force (IETF) standard that combines the best features of two existing tunneling protocols: Cisco's Layer 2 Forwarding (L2F) and Microsoft's Point-to-Point Tunneling Protocol (PPTP). L2TP is an extension of the Point-to-Point Protocol (PPP), which is an important component for Access Virtual Private Networks (VPNs).
Traditional dial-up networking services only supported registered IP addresses, which limited the types of applications that could be implemented over VPNs. L2TP supports multiple protocols and unregistered and privately administered IP addresses over the Internet. This allows the existing access infrastructure such as the Internet, modems, access servers, and ISDN terminal adapters (TAs) to be used.
L2TP can be initiated wherever PPTP or L2F is currently deployed, and can be operated as a client initiated tunnel such as PPTP, or a network access server (NAS) initiated tunnel such as L2F.
The current implementation of L2TP in Cisco IOS software is dependent on a PPP connection supported on one of the directly attached interfaces. A dial-up PPP connection is required in order to initiate an L2TP Tunnel connection. This is a requirement of the L2TP Access Concentrator (LAC). Currently the Cisco uBR900 series cable access router cannot function as the LAC; it can only function as the L2TP Network Server (LNS), which terminates a tunnel created elsewhere in the network.
Easy IP
Dynamic Host Configuration Protocol (DHCP) Server
Cisco uBR900 series cable access routers support Intelligent DHCP Relay and DHCP Client functionality. A DHCP Relay Agent is any host that forwards DHCP packets between clients and servers. A DHCP Relay Agent enables the client and server to reside on separate subnets. If the Cisco IOS DHCP server cannot satisfy a DHCP request from its own database, it can forward the DHCP request to one or more secondary DHCP servers defined by the network administrator using standard Cisco IOS IP helper-address functionality.
Network Address Translation and Port Address Translation (NAT/PAT)
Network Address Translation (NAT) reduces the need for globally unique IP addresses. NAT allows an organization with addresses that are not globally unique to connect to the Internet by translating those addresses into globally routable address space.
Port Address Translation (PAT) is a similar mechanism that enables all internal hosts to share a single registered IP address (many-to-one translation). NAT/PAT:
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Routing protocols will run on the Ethernet interface instead of the cable interface, and all packets received are translated to the correct private network IP address and routed out the Ethernet interface. This eliminates the need to run RIP on the cable interface.
To implement NAT on the Cisco uBR900 series, the Ethernet interface is configured with an "inside" address and the cable interface is configured with an "outside" address. The Cisco uBR900 series also supports configuration of static connections, dynamic connections, and address pools.
Voice Over IP Operations
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The Cisco uBR924 cable access router uses packets to transmit and receive digitized voice over an IP network. Voice signals are packetized and transported in compliance with H.323 or Simple Gateway Control Protocol (SGCP). H.323 is an International Telecommunications Union (ITU) standard that specifies call signaling and control protocols for a shared IP data network. SGCP is a Cisco/Bellcore-developed, out-of-band signaling protocol under review by the Internet Engineering Task Force (IETF).
illustrates a broadband cable system that supports VoIP transmission. Quality of Service (QoS) and prioritization schemes are used to enable real-time (voice) and non-real-time traffic to coexist on the same channel. The CMTS routes IP telephony calls intermixed with other data traffic.
Figure 4 Simplified VoIP Over Cable Network
Your company can then deploy IP telephony as a local-loop bypass service where voice packets are transferred from the CMTS to:
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The gatekeeper or call agents manage voice calls. The gateway interconnects the IP network to the public switched telephone network (PSTN).
Voice calls are digitized, encoded, compressed, and packetized in the originating gateway, then decompressed, decoded, and reassembled in the destination gateway. A server maintains subscriber profiles and policy information.
You can place and receive calls without using the local exchange carrier. Two simultaneous voice and fax calls are supported to and from each subscriber site. Multiple telephones and fax devices can be connected to each of the two VoIP telephone lines at a subscriber site, providing the 5 REN limit is adhered to for each telephone line.
Note the following requirements and characteristics of VoIP applications using the Cisco uBR924 cable access router:
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Contact your network management, provisioning, or operations team to determine what your network supports.
Voice Handling
The Cisco uBR924 cable access router supports the following compression and decompression algorithms (CODECs):
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CautionBecause voice transmission is delay-sensitive, a well-engineered network is critical. Fine-tuning your network to adequately support VoIP typically involves a series of protocols and features geared to support Quality of Service (QoS).
To achieve acceptable voice quality and reduce network bandwidth usage, several voice processing techniques and services are employed, including echo cancellation, voice compression, Voice Activity Detection (VAD) or silence compression, and Dual Tone Multi- Frequency (DTMF) tone detection and generation.
The Cisco uBR924 cable access router supports multiple QoS service IDs (SIDs), enabling multiple classes of service on the cable interface. This enables VoIP and data traffic to be treated separately, with all data assigned to a default class of service, while VoIP traffic is assigned to a different class of service. Thus, voice traffic from the Cisco uBR924's telephone ports can take precedence over the data traffic coming from the Ethernet interfaces.
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If the Cisco uBR924 interoperates with a DOCSIS 1.0 CMTS that does not support multiple CoS per router, voice traffic will be transmitted on a "best effort" basis along with data traffic. This may cause poorer voice quality and lower data throughput when calls are being made from the router's telephone ports.The Cisco uBR924 cable access router supports the following service classes:
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This service class results in the assignment of a primary SID for the router. In addition to being used as a data SID, the router uses this SID for all MAC message exchanges with the CMTS. Any SNMP management traffic from the network to the Cisco uBR924 will also use this SID.
While this class is strictly "best effort," data traffic within this class can be prioritized into eight different priority levels. The CMTS system administrator, however, must define the supported upstream traffic priority levels and include the traffic priority fields in the configuration file downloaded to the Cisco uBR924.
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The multiple SID-per-router feature enables the Cisco uBR924 to use multiple SID queues for differentiated services. The Cisco uBR924 diverts voice call traffic to the higher QoS secondary SID, while forwarding "best effort" data from the Ethernet interface and MAC messages on the primary SID.
H.323 Protocol Stack
H.323 is an International Telecommunications Union (ITU) standard that specifies call signaling and control protocols for a shared IP data network. The Cisco uBR924 cable access router acts as an H.323 gateway. In architectures using the VoIP H.323 protocol stack, the session application manages two call legs for each call: (1) a telephony leg managed by the voice telephony service provider; (2) the VoIP leg managed by the cable system operator—the VoIP service provider. Use of the H.323 protocol typically requires a dial plan and mapper at the headend or other server location to map IP addresses to telephone numbers.
When both legs of the call have been set up, the session application creates a conference between them. The opposite leg's transmit routine for voice packets is given to each provider. The CMTS router passes data to the gateway and gatekeeper. The H.323 stack provides signalling via H.225 and feature negotiation via H.245.
To make and receive H.323 calls, the Cisco uBR924 cable access router must know:
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SGCP Protocol Stack
The Cisco uBR924 cable access router supports Simple Gateway Control Protocol (SGCP), an out-of-band signaling protocol that interacts with an external call agent (CA) to provide call setup and teardown for VoIP calls made through the Internet or a local intranet. Using the call control agent, SGCP communicates with the voice gateways, allowing you to create a distributed system that enhances performance, reliability, and scalability while still appearing as a single VoIP gateway to external clients. SGCP eliminates the need for a dial plan mapper and static configuration on the router to map IP addresses to telephone numbers because this function is provided by the external call agent.
In architectures using the SGCP protocol stack, the session application implements the gateway functionality defined to support both trunk and residential gateways. The Cisco uBR924 functions in this mode as a residential gateway with two endpoints.
SGCP can preserve Signaling System 7 (SS7) style call control information as well as additional network information such as routing information and authentication, authorization, and accounting (AAA) security information. SGCP allows voice calls to originate and terminate on the Internet, as well as allowing one end to terminate on the Internet and the other to terminate on a telephone or PBX on the PSTN.
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Voice Specifications
Backup POTS Connection
The Cisco uBR924 cable access router provides an RJ-11 port (Line) that connects to a standard analog telephone wall jack. In the event of a building power failure or a Cisco uBR924 power problem, the cutover port lets you dial out using the backup PSTN line. If the Cisco uBR924 loses power while VoIP calls are in progress, you can reestablish one of the two connections—dialing out over the PSTN.
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Security Features
Cisco uBR900 series cable access routers support the security features described in the paragraphs below.
DOCSIS Baseline Privacy
Support for DOCSIS Baseline Privacy in the Cisco uBR900 series is based on the DOCSIS Baseline Privacy Interface Specification (SP-BPI-I01-970922). It provides data privacy across the HFC network by encrypting traffic flows between the cable access router and the CMTS.
Baseline Privacy security services are defined as a set of extended services within the DOCSIS MAC sublayer. Two new MAC management message types, BPKM-REQ and BPKM-RSP, are employed to support the Baseline Privacy Key Management (BPKM) protocol.
The BPKM protocol does not use authentication mechanisms such as passwords or digital signatures; it provides basic protection of service by ensuring that a cable modem, uniquely identified by its 48-bit IEEE MAC address, can only obtain keying material for services it is authorized to access. The Cisco uBR900 series cable access router is able to obtain two types of keys from the CMTS: the Traffic Exchange Key (TEK), which is used to encrypt and decrypt data packets, and the Key Exchange Key (KEK), which is used to decrypt the TEK.
IPSec Network Security
IPSec Network Security (IPSec) is an IP security feature that provides robust authentication and encryption of IP packets. IPSec is a framework of open standards developed by the Internet Engineering Task Force (IETF) providing security for transmission of sensitive information over unprotected networks such as the Internet. IPSec acts at the network layer (Layer 3), protecting and authenticating IP packets between participating IPSec devices ("peers") such as the Cisco uBR900 series cable access router.
IPSec provides the following network security services:
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Triple Data Encryption Standard
The Data Encryption Standard (DES) is a standard cryptographic algorithm developed by the United States National Bureau of Standards. The Triple DES (3DES) Cisco IOS Software Release images increase the security from the standard 56-bit IPSec encryption to 168-bit encryption, which is used for highly sensitive and confidential information such as financial transactions and medical records.
Firewall
Cisco uBR900 series cable access routers act as buffers between any connected public and private networks. In firewall mode, Cisco cable access routers use access lists and other methods to ensure the security of the private network.
Cisco IOS firewall-specific security features include:
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For additional information, see the description of the Cisco IOS Firewall Feature Set in the Cisco Product Catalog, or refer to the sections on Traffic Filtering and Firewalls in the Security Configuration Guide and Security Command Reference available on Cisco Connection Online (CCO) and the Documentation CD-ROM.
NetRanger Support—IOS Intrusion Detection
NetRanger is an Intrusion Detection System (IDS) composed of three parts:
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Configuration Options
The Cisco uBR900 series cable access router typically ships from the factory ready to work in the Base IP Bridging (DOCSIS-compliant bridging) data-only mode. The cable access router is configured automatically at startup by one or more configuration files generated by the cable service provider and downloaded to the router; no configuration or setup is required other than to connect the router to the cable system. The CMTS provides a path from the cable access router to the DHCP server for PC address assignment.
The PCs connected to the Cisco uBR900 series must be configured for Internet Protocol (IP). Using DHCP, the CMTS assigns an IP subnet address to the cable access router each time it connects to the network. The IP addresses of the cable access router and the individual PCs attached to it enable the CMTS to route data to and from the PCs.
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The configuration file or files downloaded to the Cisco uBR900 series by the CMTS at the headend are dependent on the services purchased by the individual cable service subscriber. The cable access router is provisioned in the following manner:
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To ensure that you obtain the exact services that you have ordered, the Cisco uBR900 series arrives from the factory with a unique identifier (UID) that consists of a serial number and MAC address. These factory-assigned values are on a label at the bottom of the cable access router; for convenience, these values are also in a barcode label that can be easily scanned for entry into the service provider's provisioning and billing system.
Using the MAC address of the cable access router as the key, the CMTS downloads the DOCSIS configuration file and Cisco IOS image that will provide the services that you have purchased. Service technicians at the headend typically create a number of standard configuration files to match the range of services offered by the provider; these configuration files can be created manually or with tools provided for this purpose by Cisco Systems.
The following sections describe the initial power-on and provisioning sequences in more detail, as well as the requirements that must be met by both the cable access router and the CMTS before provisioning can be successful.
Initial Power-On Sequence
When connected and first powered on, the Cisco uBR900 series cable access router performs the following boot procedures:
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Next, the Cisco uBR900 series performs a series of DOCSIS-mandated procedures for automatic installation and configuration. These procedures are summarized in and in .
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At this point the router is online and operational in the basic DOCSIS bridging ("plug and play") mode. If the DOCSIS configuration file specifies that the router must download a Cisco IOS image and a Cisco IOS configuration file, the router uses TFTP to download the image and configuration file into its local memory. It then installs the new IOS image and runs the configuration file.
Downloading a DOCSIS configuration file to a Cisco uBR900 series cable access router automatically:
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Telnet access to the router from the headend is still allowed, but only if the Cisco IOS configuration file includes enable and line vty passwords; if the configuration file does not include enable and line vty commands to specify these passwords, Telnet access and console access are both disabled.
The sequence numbers shown in are also shown in below. The Cisco uBR900 series cable access router will complete all the steps shown in the table and flowchart each time it needs to reregister with the CMTS.
Figure 5 Cable Modem Initialization Flowchart
illustrates the traffic flow during the initialization process.
Figure 6
Cisco uBR900 Series Cable Access Router Provisioning Overview
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After the Cisco uBR900 series cable access router goes online, it begins transferring data between the attached CPE devices and the network (internet, intranet, VoIP). The cable service provider typically uses DHCP to assign IP addresses to the CPE devices. The number of IP addresses each subscriber can obtain depends on the services purchased from the provider.
Basic Troubleshooting
A MAC-layer circular log file is stored inside the Cisco uBR900 series cable access router. This file contains a history of the log messages such as state event activities and timestamps. This is the most valuable information for troubleshooting the cable interface.
The MAC log file is displayed by entering the show controllers cable-modem 0 mac log command from privileged EXEC mode.
The most useful display fields in this output are the reported state changes. These fields are preceded by the message CMAC_LOG_STATE_CHANGE. These fields show how the Cisco uBR900 series progresses through the various processes involved in establishing communication and registration with the CMTS. The normal operational state is maintenance_state ; the normal state when the interface is shut down is wait_for_link_up_state.
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The following is the normal progression of states as the Cisco uBR900 series registers with the CMTS:
wait_for_link_up_stateds_channel_scanning_statewait_ucd_statewait_map_stateranging_1_stateranging_2_statedhcp_stateestablish_tod_statesecurity_association_stateconfiguration_file_stateregistration_stateestablish_privacy_statemaintenance_stateFollowing is an example of a MAC log file for a cable access router that has successfully registered with the headend CMTS. The output that is displayed is directly related to the messages that are exchanged between the Cisco uBR900 series and the CMTS.
uBR924# show controllers cable-modem 0 mac log508144.340 CMAC_LOG_DRIVER_INIT_IDB_RESET 0x08098FEA508144.342 CMAC_LOG_LINK_DOWN508144.344 CMAC_LOG_LINK_UP508144.348 CMAC_LOG_STATE_CHANGE ds_channel_scanning_state508144.350 CMAC_LOG_WILL_SEARCH_DS_FREQUENCY_BAND 88/453000000/855000000/6000000508144.354 CMAC_LOG_WILL_SEARCH_DS_FREQUENCY_BAND 89/93000000/105000000/6000000508144.356 CMAC_LOG_WILL_SEARCH_DS_FREQUENCY_BAND 90/111250000/117250000/6000000508144.360 CMAC_LOG_WILL_SEARCH_DS_FREQUENCY_BAND 91/231012500/327012500/6000000508144.362 CMAC_LOG_WILL_SEARCH_DS_FREQUENCY_BAND 92/333015000/333015000/6000000508144.366 CMAC_LOG_WILL_SEARCH_DS_FREQUENCY_BAND 93/339012500/399012500/6000000508144.370 CMAC_LOG_WILL_SEARCH_DS_FREQUENCY_BAND 94/405000000/447000000/6000000508144.372 CMAC_LOG_WILL_SEARCH_DS_FREQUENCY_BAND 95/123015000/129015000/6000000508144.376 CMAC_LOG_WILL_SEARCH_DS_FREQUENCY_BAND 96/135012500/135012500/6000000508144.380 CMAC_LOG_WILL_SEARCH_DS_FREQUENCY_BAND 97/141000000/171000000/6000000508144.382 CMAC_LOG_WILL_SEARCH_DS_FREQUENCY_BAND 98/219000000/225000000/6000000508144.386 CMAC_LOG_WILL_SEARCH_DS_FREQUENCY_BAND 99/177000000/213000000/6000000508144.390 CMAC_LOG_WILL_SEARCH_SAVED_DS_FREQUENCY 699000000508145.540 CMAC_LOG_UCD_MSG_RCVD 3508146.120 CMAC_LOG_DS_64QAM_LOCK_ACQUIRED 699000000508146.122 CMAC_LOG_DS_CHANNEL_SCAN_COMPLETED508146.124 CMAC_LOG_STATE_CHANGE wait_ucd_state508147.554 CMAC_LOG_UCD_MSG_RCVD 3508147.558 CMAC_LOG_UCD_NEW_US_FREQUENCY 20000000508147.558 CMAC_LOG_SLOT_SIZE_CHANGED 8508147.622 CMAC_LOG_FOUND_US_CHANNEL 1508147.624 CMAC_LOG_STATE_CHANGE wait_map_state508148.058 CMAC_LOG_MAP_MSG_RCVD508148.060 CMAC_LOG_INITIAL_RANGING_MINISLOTS 40508148.062 CMAC_LOG_STATE_CHANGE ranging_1_state508148.064 CMAC_LOG_RANGING_OFFSET_SET_TO 9610508148.066 CMAC_LOG_POWER_LEVEL_IS 28.0 dBmV (commanded)508148.068 CMAC_LOG_STARTING_RANGING508148.070 CMAC_LOG_RANGING_BACKOFF_SET 0508148.072 CMAC_LOG_RNG_REQ_QUEUED 0508148.562 CMAC_LOG_RNG_REQ_TRANSMITTED508148.566 CMAC_LOG_RNG_RSP_MSG_RCVD508148.568 CMAC_LOG_RNG_RSP_SID_ASSIGNED 2508148.570 CMAC_LOG_ADJUST_RANGING_OFFSET 2408508148.572 CMAC_LOG_RANGING_OFFSET_SET_TO 12018508148.574 CMAC_LOG_ADJUST_TX_POWER 20508148.576 CMAC_LOG_POWER_LEVEL_IS 33.0 dBmV (commanded)508148.578 CMAC_LOG_STATE_CHANGE ranging_2_state508148.580 CMAC_LOG_RNG_REQ_QUEUED 2508155.820 CMAC_LOG_RNG_REQ_TRANSMITTED508155.824 CMAC_LOG_RNG_RSP_MSG_RCVD508155.826 CMAC_LOG_ADJUST_RANGING_OFFSET -64508155.826 CMAC_LOG_RANGING_OFFSET_SET_TO 11954508155.828 CMAC_LOG_RANGING_CONTINUE508165.892 CMAC_LOG_RNG_REQ_TRANSMITTED508165.894 CMAC_LOG_RNG_RSP_MSG_RCVD508165.896 CMAC_LOG_ADJUST_TX_POWER -9508165.898 CMAC_LOG_POWER_LEVEL_IS 31.0 dBmV (commanded)508165.900 CMAC_LOG_RANGING_CONTINUE508175.962 CMAC_LOG_RNG_REQ_TRANSMITTED508175.964 CMAC_LOG_RNG_RSP_MSG_RCVD508175.966 CMAC_LOG_RANGING_SUCCESS508175.968 CMAC_LOG_STATE_CHANGE dhcp_state508176.982 CMAC_LOG_DHCP_ASSIGNED_IP_ADDRESS 188.188.1.62508176.984 CMAC_LOG_DHCP_TFTP_SERVER_ADDRESS 4.0.0.1508176.986 CMAC_LOG_DHCP_TOD_SERVER_ADDRESS 4.0.0.32508176.988 CMAC_LOG_DHCP_SET_GATEWAY_ADDRESS508176.988 CMAC_LOG_DHCP_TZ_OFFSET 360508176.990 CMAC_LOG_DHCP_CONFIG_FILE_NAME platinum.cm508176.992 CMAC_LOG_DHCP_ERROR_ACQUIRING_SEC_SVR_ADDR508176.996 CMAC_LOG_DHCP_COMPLETE508177.120 CMAC_LOG_STATE_CHANGE establish_tod_state508177.126 CMAC_LOG_TOD_REQUEST_SENT508177.154 CMAC_LOG_TOD_REPLY_RECEIVED 3107617539<508177.158 CMAC_LOG_TOD_COMPLETE
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