Requesting /60 From Xfinity?

Installing and Using OpenWrt
1

There's a really great overview of possibly getting a /60 from residential Xfinity here:

I'm trying to find which settings I need to change in OpenWRT to so.

1. Bridge Mode on Xfinity Gateway

This is easy enough, but it also seems to require plugging my router into the correct port on it's back.

Questions:

  • Which port? Is it the one with the red dot?

  • Will the Xfinity App's Security Blocking be effected by putting the Xfinity Gateway in bridge mode?

  • If I wish to do some debugging ala tcpdump or wireshark, should I wait to plug the router into the Xfinity Gateway until I have tcpdump or wireshark running?

2. OpenWRT WAN Side Settings?

After reviewing the aforementioned Xfinity Thread, the following OpenWRT WAN Settings seem to be involved, but some of these I'm not sure which are which:

| config | | option | Value |
| ========= | ======= | ================= | ================= |
| interface | wan6 | device | eth1 |
| interface | wan6 | proto | dhcpv6 |
| interface | wan6 | clientid | xx:xx:xx:xx:xx:xx |
| device | ??? | DUID | ???? |
| globals | globals | dhcp_default_duid | ???? |
| | | reqaddress | force |
| | | reqprefix | 60 |
| | | Send prefix hint? | ??? |
| | | IA_PD??? | ??? |
| | | DHCPv6-PD | ???? |

3. tcpdump settings / Wireshark?

I know I should be looking at port 567 and 568 for packets relating to RA and RS packets but beyond that I'm not really sure what to look for.

4. Running ip -6 addr to look for the correct WAN6 address to see if we got a /60

5. CMTS

The document also says something about

CMTS (Cable Modem Termination System) in a specific neighborhood, that hardware literally might not be configured to hand out anything but /64s.

I don't know if maybe there's a way to detect that.

2

I have Xfinity now. I don't use Openwrt as my firewall, but I can get a /60 from them and split that into subnets on my own network. So I can't tell you how to configure it with Openwrt, but I can confirm it is possible to receive at least /60. I actually make a PD request for a /60 for the subnets and also an NA request for a /64 address for the WAN port. For me, the prefix is allocated, and then the various nics get assigned a /64 on different subnets. I think I could configure it so that the nics would get a /62 or /60, for example, but I haven't tried.

I used to have Comcast Business with static IPs until they started hiking up my rates. I don't think that would have anything to do with it since my delegated prefix is completely different and will change infrequently.

Before you use wireshark, I would look at the logs to verify that the request is being made and/or set logging to be more verbose.

Good luck!