nanog mailing list archives
Re: [HFC] pooling modems in layer2
From: charles () thefnf org
Date: Tue, 12 Aug 2014 12:51:23 -0500
On 2014-08-12 09:23, Toney Mareo wrote:
Hello I think it's kind of an isp secret but I would be curious how do people distribute modems to pools before they would even reach the actual IP network so on layer2: http://dl.packetstormsecurity.net/papers/evaluation/docsis/Service_Distribution.jpg For this I would like to get some clarification because I do not work in the telco industry. As I can figure out of the docsis, cablelabs documents. The CMTS device is connected to the coax segments through fiber. Therefore one could say that the "modem facing" side is a fiber optic interface but it's not 1000 Base-FX, not a regular Ethernet over fiber. It sends signals through a broad range of frequencies.
Sounds about right to me.
So what I would like to accomplish to provide a different pool of dhcp servers, which provides different config file, tod server, router, dns etc. infos to the modems but to do all this in Layer2.
Why? Do you have a bunch of cable modems and a CMTS? If so, does the documentation not cover this? Or are you trying to hack your cable modem/cable provider?
I don't have hands on experience with CMTS-es but I would think that they are able to pool clients by MACs and able to send eg 500 clients to DHCP server1 and the other 1500 to DHCP server2 before they would even get an IP, so I talking of pure layer2 here! Let's say if the CMTS device does not support this, what are the other options for routing layer2 traffic coming out of the CMTS?
Um. Probably via RADIUS and via VLAN assignment? If I would
know more about the device I would say that put a linuxbox after it (on the ISP facing nic) and mark the packets going out with arptables/ebtables then send them out of different nics to different dhcp servers.
Most likely they just use VLANs. This rack of CMTS gear is on port 22 of the agg switch, vlan 2 and ip helper is set for vlan 2 to the desired dhcp server (which is most likely an HA floating IP if not a full blown VIP etc).
Current thread:
- [HFC] pooling modems in layer2 Toney Mareo (Aug 12)
- Re: [HFC] pooling modems in layer2 charles (Aug 12)
- Re: [HFC] pooling modems in layer2 Scott Helms (Aug 12)
- Re: [HFC] pooling modems in layer2 Toney Mareo (Aug 14)
- Re: [HFC] pooling modems in layer2 Scott Helms (Aug 14)
- Re: [HFC] pooling modems in layer2 Toney Mareo (Aug 14)
- Re: [HFC] pooling modems in layer2 Rob Seastrom (Aug 12)
- Re: [HFC] pooling modems in layer2 Scott Helms (Aug 13)