Cable Modem Link Aggregation



  • @derelict I’ll give that a shot. I have a docsis 3.1 emta with the gig service, one my 4 port nic gets here I’m gonna test the link aggregation on these 3.1 modems. :)


  • Netgate

    Split to avoid a hijack.

    Interesting. Where is the documentation on this link aggregation?

    I don't feel like buying a new modem right now so I'm at 300/30.



  • so most of the docsis 3.1 modems come with multiple ethernet ports, the only thing I can make sense of is that it is for link aggregation. I dont think its officially supported yet but I want to try. :) Full disclosure, I do work for that ISP and have been trying to get an answer from the product managers to no avail.



  • @dxmaster said in Cable Modem Link Aggregation:

    so most of the docsis 3.1 modems come with multiple ethernet ports, the only thing I can make sense of is that it is for link aggregation.

    Those multiple ports are used to connect more than one computer to it. Not everyone runs a separate firewall/router. Don't forget, both ends have to support aggregation and you need multiple computers or other devices to get much benefit.



  • @jknott I get that but the advertising on all the 3.1 modems boast about link speeds and capabilities higher than 1G. The only way to do that with a modem with gigabit ports would be link aggregation. Also, that would require ISPs to dish out multiple IPs which they won't do. I dont see any other reason to have multiple ethernet ports on a modem other than for link aggregation. If it was for having multiple IPs without needing a router they would've done that on modems ages ago and have never done that on any modems up until these new 3.1 modems.



  • @dxmaster said in Cable Modem Link Aggregation:

    @jknott I get that but the advertising on all the 3.1 modems boast about link speeds and capabilities higher than 1G. The only way to do that with a modem with gigabit ports would be link aggregation. Also, that would require ISPs to dish out multiple IPs which they won't do.

    Well, 4 computers, each with a gigabit port, plugged into 4 ports on the modem might do it. Also, since NAT is typically used on IPv4, the number of IP addresses available isn't an issue. Also, many ISPs are now providing IPv6, which means at least 18.4 billion, billion addresses available. At the moment, my cable modem is in bridge mode, but if I put it in gateway mode, i could connect 4 computers to it, each with a Gb interface. Aggregation would make sense, if I was connecting to a separate router, but I doubt typical modems would support it.

    BTW, large businesses, on fibre, don't use modems. They use media converters, to convert between fibre and copper. I have worked with both dumb converters and managed ones from Ciena. Any routers or firewalls are separate boxes from the media converters.



  • https://forum.netgate.com/topic/122459/wan-port-bonding-link-aggregation-group-docsis-3-1/4

    Theres a link to the topic here on netgate. :) And the use ONTs on fiber GPON setups. Just take my word for it, the multiple ports on the back of a cable modem are for link aggregation and nothing more. I think you might be getting them confused with cable gateways which are routers with a cable modem built in. Two totally different products.


  • Netgate

    I can see some form of lagg if the modem can talk > 1gig upstream. If it's just LACP or something reasonably-ubiquitous it should work fine with pfSense.

    Wish they'd just run fiber already.



  • @derelict fiber is nice, but community fiber still has inherent issues. I work with it daily so I see those issues lol


  • Netgate

    @dxmaster said in Cable Modem Link Aggregation:

    https://forum.netgate.com/topic/122459/wan-port-bonding-link-aggregation-group-docsis-3-1/4

    Last post there says LACP which is promising.

    Lots of talk there about hashing and balancing the load. By default, pfSense (FreeBSD) hashes using the following:

    l2	 src/dst mac address and optional vlan number.
    l3	 src/dst address for IPv4 or IPv6.
    l4	 src/dst port for TCP/UDP/SCTP.
    

    But that is only for sending. I would expect the modem to have an effective hashing method for general internet traffic between only two MAC addresses as well. Should work fine.



  • @jknott said in Cable Modem Link Aggregation:

    Those multiple ports are used to connect more than one computer to it. Not everyone runs a separate firewall/router.

    That is not what the manufacturers are advertising..

    This paragraph from the Motorola MB8600 page seems to contradict itself a little but the contradiction aside it does work both ways.

    Most cable companies do not allow more than one device directly behind a residential cable modem. I was lucky as mine allowed two. Commercial more.. As a commercial customer now, I use port lagg on one router and a third port for my second test router I have on premises here.

    Since my spur office DSL connection can bond two dsl circuits into a single WAN (before PPPoe (so no MLPPP needed)) I have to assume that they got ethernet bonding pretty much figured out for these modems. It appears to work very well. Im not subscribed to speeds of a gig yet so cannot verify but my router does pass traffic across both interfaces without errors or packet loss.

    Later versions of the MB8600 firmware have a switch to turn on port bonding on the modem side.

    https://motorolanetwork.com/mb8600.html



  • @chpalmer said in Cable Modem Link Aggregation:

    This paragraph from the Motorola MB8600 page seems to contradict itself a little but the contradiction aside it does work both ways.

    Does the modem have a configuration for aggregation? That's something that has to be supported at both ends.

    I have a Hitron cable modem, configured in bridge mode. I can access the modem at 192.168.100.1, but don't see anything that can be configured, let alone aggregation. All I can do is read info. So, if your modem supports aggregation, it should have some settings for it.



  • @jknott

    Hitrons are generally the ones with Puma6 or 7 chipsets that need to all be burned IMHO.. http://badmodems.com

    They are very similar to Linksys models and actually burn quite easily.. https://www.youtube.com/watch?v=J2Srun_-d4E (That was actually kinda fun to do!)

    The burning Arris modem on the badmodems site had to be equipped with a flammable gelatin for it to burn at all in that picture that is on the front page. (Im not an Arris fan but in this case good for them.)

    But I digress..

    I have the earlier firmware. I use FEC. I see it successfully passing traffic on both links with no ill effect.

    Is it right? I don't know. But it works at my advertised speed just fine.

    In the new firmware I understand people have turned the switch on (getting the blue LAN light indicating bonded ports) and that its working. I believe they are using LACP or similar available in their chosen router but Im not sure. ( Seems the ISP does not have to be in the mix after-all as some posters of another site have stated..)



  • Just as an update here.. My cable company updated my firmware on my MB8600 so now I have the checkbox to allow me to turn on port bonding.

    Using LACP works just fine with no change in latency between the modem and my router.



  • Does anyone know if this can be done with the SG-3100? I was trying to put the wan/opt1 ports into a lag, but it wont let you put any of them in a lag.. I'm guessing this is something you need custom hardware and dedicated nics for?