Docsis Config File

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Agalia Valcin

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Aug 4, 2024, 2:57:24 PM8/4/24

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Theprogram is built on top of the powerful Perl based DOCSIS::ConfigFile library. Have a look at the complete configuration parameters to see what is possible or simply try out an example config and start editing.

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Cisco Cable Modem (CM) cards allow you to connect CMs on the Hybrid Fiber Coaxial (HFC) network to a Cisco uBR7200 series in a Cable Television (CATV) headend facility. The CM cards provide the interface between the Cisco uBR7200 series Peripheral Component Interconnect (PCI) bus and the Radio Frequency (RF) signal on the HFC network.

The information presented in this document was created from devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If you are working in a live network, ensure that you understand the potential impact of any command before using it.

Configuration data for a specific CM MUST be contained in a file that is downloaded to the CM using Trivial File Transfer Protocol (TFTP), a simplified version of FTP. The configuration file is in the format defined for DHCP vendor extension data, and MUST consist of a number of configuration settings. All CMs, regardless of vendor, require configuration files. There are both standard fields and vendor specific fields within the file. The file format and the standard fields are defined in the DOCSIS specification.

The configuration file in its final form is a binary file, and typically a configuration tool is used to create the file. There are many publicly available tools to assist in the creation of DOCSIS CM configuration files. Please see Cisco's Standalone DOCSIS configuration file editor.

After a CM completes the ranging adjustment, it establishes IP connectivity through use of a DHCP. A DHCP server provides the IP information necessary for the modem to establish IP connectivity, including its IP address, the IP addresses of the TFTP server for download of the CM configuration file, and other parameters as described below.

For DOCSIS 1.0 cable modems, the Vendor Class Identifier (Option 60) MAY be set to include the string "docsis 1.0". For modems running higher versions of DOCSIS a string indicating the capabilities of the Cable Modem MUST be included in the Vendor Class Identifier (Option 60) (For example "docsis1.1:xxxxxx" where xxxxxx is an ASCII representation of the modem capabilities.

In order for CPE devices connected to the CM to be granted network connectivity, the Network Access value must be set to 1. Also, the CM needs a profile for Class of Service depending on the service level agreement with the customer.

One important note to make is that on the CM configuration file the value is entered from 1-6 and the Cisco uBR72xx router sends a UCD from 0-5. If a value of zero is used for the Upstream Channel ID configuration setting, this typically indicates to a dual modem telephone company (telco)-return/two-way CM that it should use the telco-return mode of operation.

If the CMTS is DOCSIS 1.1 enabled then at least one of the Baseline Privacy configurations settings must be configured. This means that one of Authorize Wait Timeout, Reauthorize Wait Timeout, Authorization Grace Time, Operational Wait Timeout, Rekey Wait Timeout, TEK Grace Time or Authorize Reject Wait Timeout must be set.

I've been tasked with adding DOCSIS service to some apartments we manage. Most of my experience so far is in running the ethernet network at the adjacent property and building/maintaining the analog cable system at that property. We are about to launch a Dish Network QAM system for both properties as well as cable modem service for the smaller property where we only have existing RG6 to work with. There are 64 units.

I already have an Arris CMTS 1500. Modems are Motorola SB5101. What I'm wanting to accomplish is to have the cable modem network operate as a layer 2 bridge. I currently do all access control and provisioning elsewhere for our wired eithernet network at the larger property (132 units) and our wireless service. I want to manage the cable modem users the same way. Is there a way I can set up a single config with no bandwidth limitations but possibly some blocking to prevent rogue dhcp servers? I want to have the MAC addresses of the modems I've ordered authorized so I can just throw a modem out there and provision an IP to whatever device the user has behind the modem.

Will the Arris CMTS/Motorola modems allow me to put the cmts on our management network and tag another vlan for the default on the ethernet port of the modem. I want the modem to be in vlan 2 where I can manage it but I want the CPE in vlan 20.

I'm using mikrotik for routing and dhcp. I'm not wanting to change things too much as I have a system that works very well for managing our customers and already have quite a bit of integration with our billing system (platypus)

I already have the RF side under control, we're in the process of building new fiber to the smaller property and have had fiber at the larger property all along. I've moved most of the larger property over to an HFC system using fiber equipment from Multicom. I have 2x 13dbm fiber transmitters, one for each property, 2x 8 way optical splitters and 8 return path receivers for the 8 buildings at the smaller property. No return path for the larger property as they already have ethernet jacks in the units. Our company is over the management of 20 properties across the US, most of which are owned by the parent company. as such, we have become our own PCO, just got approval from Dish 3 weeks ago.

(PacketAce) -- If you are eligible for Arris support either by buying a support contract with Arris or being a member of the CoOp, you can gain access to PacketAce which is a good click and add type config generator. Its main drawback besides not being readily available is that you cannot add non Arris Specific Oids to the config.

With an Arris 1500 you will want docsis 1.0 configs I believe and they are the easiest to create there are several example configs included with docsis.sourceforge.net I would suggest starting there, also reading the relevant cable labs specs for docsis 1.0 could not hurt either.

Tough Question, I am not sure if the Arris 1500 supports VLAN tagging for the CPEs Cisco CMTSes do but it is a pain in the Butt mostly only used for p2p vpns. I don't think anyone supports having the modems in a separate vlan than the cpes. This is because Modems are not routers or even switches Modems are transparent bridges, they are addressable but they do not route traffic. If you want to prevent CPEs from talking to the modem network this can be accomplished with IP filters which would go in the modem config file. I would get the network working properly before attempting this step because it will take a bit to get it right. On a related side note due to not being able to separate the modem and cpe traffic with VLANs it is a good Idea to physically separate the networks i.e. modems get a 10.x.x.x ip and cpes get a routeable or natted ip.

The filters yes, a generic config file with no bandwidth limitations yes (docsis1.0) but probably not what you want to do. Docsis has bandwidth control built into the spec, in docsis 1.0 it is not very flexible but it seems silly to completely bypass the bandwidth controls on the CMTS to use the bandwidth controls on the Microtik as the CMTS probably has 10x the processing power of the microtik. Not to mention the CMTS allocates bandwidth based on RF-bandwidth available whereas doing that with the microtik is not possible. Bandwith allocation is usually done in the config file by either specifying the max bandwidth (docsis 1.0) or service Class name (docsis1.1+) and then specifying the bandwidth for that class in the cmts.

provisioning a CM and the CPE behind it is usually is as easy as creating a host entry in dhcpd for the modem with the config file name and optionally configuring a host entry for the CPE if you need to specify something i.e. a static IP otherwise just deny unknown clients to the modem subnet and allow unknown clients to the client subnet that way if a modem is authorized(host entry in dhcpd) any client behind it can connect and get dhcp if it does not have a host entry the modem will not come online. Not sure how different this is from your existing setup but it should be pretty close with the exception of the inline bridge (cable modem).

If you use dhcpd you will want to make use of shared-networks because the CPEs will have dhcp requests coming from the CMTSes IP i.e. the CMTS will become a dhcp relay, here is a sample config assuming 10.0.0.0/24 for the modems and 192.168.0.0/24 for the cpes

Thanks for the pointers, I was able to get our test system working well today, we have a dhcpd config with groups for our different plans, doing rate limiting works out good on the modem just a little extra config.

The Mikrotik box in question has plenty of power, 2x dual core opteron in a dell sc1435. We're using it on a 100mb fiber connection currently, all hardware designed to handle at least 1gbps if we ever grow that far.

Would anyone here recommend going with docsis-server? or just continue where i'm at now and write a couple scripts to manage dhcp entries for modems? keep in mind I will only ever have a max of 64 cable modems on this system, the rest of our network is ethernet over fiber, copper and wireless.