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cmts laboratory environment

Hi everyone,

i would like to know if you have any idea about how to "build" kind of simple CMTS environment for using in laboratory. something
like a card (ethernet -> coax? pci? usb?)... do you know if have any product like that?

because in my project, i need to provide internet access for cable modem like a SVG1202[1]

Can't say I have ever seen a

Can't say I have ever seen a PC-based system...

You should be able to buy a surplus DOCSIS 2.0 CMTS with 1 linecard for next to nothing.

If you google for "Cisco CMTS all in one" you will see examples of how to config the CMTS to provide all the required DHCP and TFTP stuff.

Then its pretty easy to wire up some coax cables from the CMTS DS and US ports to give you a way to boot up some lab modems.

Not easy as this like

Well, your question can be possible using into two differents kind of technology. First, what do you want to do?

If you only want send ethernet frame into a COAX to expand a network infrastructure, you can use theses kind of devices

Otherwise, if you have to provide a real Cable Modem solution over an outdoor network (copper, RFoG, HFC, etc...) who already transport TV and others services it's not easy as 1-2-3. It's not like to connect a switch L3, adjust the routing, IP subnet and start to play.

I'm sorry, but your question like mine one year ago, and I'm sorry to scrap your dream. Since last year I've personaly deployed 5 Motorola BSR2000 and I still having issues that Motorola can't quickly fix.

Give me a favor, dont think we will share our setup and config file. It's not because we dont want help, it's because each compagny who design devices add their own specifications and depends of the needs it's not a "fits all" solutions. It's specific to each network so please dont be sad about the Forum, it's just not easy.

So starting your lab, if you really need to setup a DOCSIS Lab you'll need:

- 1x CMTS (no it's not possible to use a Linux based PC convert into a Cable router.Ok? We close this forever or until a hardware manufacturer will sell PCIExpress Coax interfaces. BUT!!!!! If you know a manufacturer who do this, please share!!)

- 1x RG-6 2way Splitter (you have to combine US/DS RF signals into a single Coax cable, yes RF splitter can combine)
- 3x RF attenuator +20dB (you are in lab, so it's not a good idea to blow up your equipments radio)
- 1x 3Way RF splitter (optional, but if you want to test 3 CM simultanously it's a good idea)
- 1x Return path filter (you are in LAB and have to combine the US and DS, so to clear the risk to have some RF signal harmonic on your DS, this filter is a good idea)
- 1x Linux Box (I've use Debian or use any distro of your choice and provide theses services: DHCP, TFTP, ToD, Syslog and DNS)
- 1x Switch L2 (to connect your Linux box, CMTS and Internet access. Use managable switch caused if you have to trouble shoot the L3 packets, wireshark and a port mirror will became your month employee)

Your connection desing, see:
You wil have to replace the fiber devices by the coax/RF spliters. They do the same job's on different cable type.

Yes you will have to put money on the table and buy devices. You can found really good deal into the refurbished market but for sure it will not free.

Ok, you have fished to read? Did this sound's you like chinese? Stop here and hire a consultant. If it's ok, you will continued with the RF plan, Cable modem DOCSIS standard, OID options, Cable modem TEK and required security, DHCP provisionning/relaying and routing.

Again it's not to affraid, discouraged or present this bigger than it is, this is the live of the Data Over Cable Service Interface Specification, or the DOCSIS.

It's really possible to do it. But always keep in mind that it's not easy, you will spend many hours without results, spend money in devices and materials but it's possible.

Good luck!


thanks so much

thanks so much for your explanation! but, let me try to explain my need...

1) I need a cmts laboratory environment... OK! after your explaination, now i gotcha! :)

2) so, in my project. i need to do some changes in "cable modem" router... but, i need know if exist some cable modem that i can have access for it. (could be by flash or ssh/telnet) something like OpenWrt, dd-wrt and whatever.... something that we can have toolchain/buildroot for can build a "changed" firmware, something like "from scratch"... someboy know if have some manufactor (model)?

you should check out the

you should check out the erouter specification it is the standard way routers and cable modems are linked together, to see if what you want to do is supported. If it is, you will need to find a hardware module that is programmable, it will be an OEM model.

heres the spec.

cmts pc-based

someone know about CMTS PC-Based ?


jpereiran. You want to provide Internet using a CMTS. With all the respect I've for you, trust me and believe my experience : Data Over Cable it's anything like easy, low cost and quick to deploy. I've post a lots of theses questions into theses Forum and unfortunately, if you want to provide DOCSIS, buy a CMTS.

You don't want to buy a CMTS, well, good luck!

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