Comcast Business - Requires multiple /64 DHCP-PD requests rather than single /60



  • After months of opening requests with Comcast, I've finally been told their design for their static IPv4 business customers is that they can't do a DHCP-PD delegation larger than a /64, even though they allocate a /56 for the customer. They will also not do static routes in IPv6. They have tested with other products that can request multiple /64 delegations, so they consider that the proper way to do it.

    I'm having no success in determining how to configure pfSense to adapt to such a crazy configuration. I can get a single /64 delegated to one of my internal networks, but I simply can't see how to setup another.

    I attempted to create a second IPv6-only external interface and connect it to the same network as the first external, but pfSense detected I was trying to add two interfaces to the same VLAN and rejected it.

    Any suggestions? Thank you.



  • I think they meant to say that they cannot do larger than a /60.

    There has been a lot of discussion of the /60 limit in the Comcast IPv6 forum.



  • Residential is usually limited to /60… Business should be limited to /56. ... [edit] Though I do see a number of posts saying that only /60 seems to be available to business customers now.

    Unless you're a residential customer with their 2Gb Gigabit Pro Metro-E fiber service… then you get a /48.

    Of course, if you request a /64 first before changing the prefix size setting then you need to delete the DUID file because Comcast will keep giving you a /64 until the lease expires or your router provides a new DUID.



  • @virgiliomi:

    Residential is usually limited to /60… Business should be limited to /56. ... [edit] Though I do see a number of posts saying that only /60 seems to be available to business customers now.

    For Business, you are allocated a /56, which you will see in your account. However, Comcast does not currently appear to have the capability to do static routing, so it needs a dynamic prefix delegation. You can request up to a /56. In theory, you should be able do multiple requests for /56 delegations with different id associations, but I haven't tested this.



  • I've not been able to figure out how to make comcast work with multiple routers at once with ipv6.

    I have 2 pfsense boxes, and when I set them both to /60 via dhcp, I get 50% packet loss on ipv6.

    I wonder if this is related?



  • Are you using the same prefix delegation ID for both systems? You might try explicitly setting the prefix delegation ID in the Advanced DHCP6 Client Configuration section to different values for the different systems.



  • They were both set to 0.

    Would that cause the issue?



  • @moscato359:

    They were both set to 0.

    Would that cause the issue?

    Yes, that is what selects which /64 is used.  With both set to 0, they're trying to use the same prefix.  Change one to another number up to 255.


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