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R

Recognized Contributor

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31 Messages

Wed, Feb 24, 2021 9:11 PM

/59 prefix delegation block changed...

I have a /56 static on Comcast Business.  Recently I had a cable modem issue (as determiend by comcast) and the cable modem was replaced.  Everything is working, but I received a different /59  (still inside my /56) so I had to renumber several vlans!  How do I keep this from changing?  

Thank you,


Robert

Responses

Recognized Contributor

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31 Messages

4 m ago

@hiryu :

Comcast just reflashed my modem and I think I'm on the same version:

DOCSIS Software Version:2.3.10.13_5.5.0.5

Software Image Name:DPC3941B_3.9p32s1_PROD_sey

Advanced Services:DPC3941B

This is from "gateway->software" menu.

New problem solver

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18 Messages

3 m ago

I am also getting  rotating IPv6 /64 addresses.  This has been happening for several years with no resolution.  Any solution?  I have two subnets that were getting a :13e0 and :13e1 (/64).  IPv6 stopped routing, so I rebooted both my router and the modem.  New addresses were :1380 and :1381.  I rebooted everything again and now they are :1360 and :1361.

My network is down because I haven't had time to go around and fix everything.

I've had a request in to support for over a week now with no solution.  I'm paying for 'static' ipv6 addresses and they aren't static.....

(edited)

Recognized Contributor

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31 Messages

3 m ago

@flyingrobots :  If you find a solution please post here. 

I check this thread occasionally, but I've moved to a 6-in-4 tunnel for ipv6 from he.net (free!!).  I'd love to do native, but @Comcast Business equipment seems to be broken beyond repair.  There is NO WAY to make sure you get the same /59 handed out!  After reunumbering my vlans 3 or 4 times, I gave up & did an HE.NET tunnel.  It's literally an hour or less to setup & then maybe an hour or two to renumber my network.  I also get a /48 and don't have to deal with dhcp-pd shenanigans.  Hopefully Comcast doesn't break 6-in-4....

The ONLY subnet that stays the same is the /64 directly behind the modem.  If you are going to use ONLY that it should work great.  If you rely on dhcp-v6 pd prefixes not changing, use another solution so you don't lose your sanity.

I don't think comcast business support realy understand the problem, doesn't care, or simply has no way to fix it and waits until you give up.

@Comcast Business : Please prove me wrong.  Contact me if you have a solution where I can be guaranteed the same /59 within a /56.  I'd love to use native ipv6 on my connection with static ips!

What I don't understand is why this has remained a problem.  There are easy (technical) fixes!

  1. Let the user put in /59 static routes in the cable modem to point to a next hop.
  2. Let the user put in a /56 static route in the cable modem to the next hop and let the user do their own delegations internally.
  3. Let the user establish BGP session(s) with a non-public AS Number (64512-65534)  customer provided PE that talks to the cable modem
    1. Comcast strips the AS# & replaces it with it's own.
    2. Comcast filters an route advertisements not inside the static /56
  4. Let users put their cable modem in bridge mode & take over all the layer 3 function with a user provided router using #2 or #3.

I'm guessing it's not fixed as this type of functionality is probably in their Metro-e/DIA offerings.

(edited)

New problem solver

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18 Messages

3 m ago

@rob__jr  yea...I thought I had found a solution, but alas, it was my hot spot connection to my phone that was getting the good results (Iphone is using ipv6).

They aren't going to fix it, and they really don't care...so I've reverted my network back to ipv4.  I've learned a lot, but need to move on...

btw: The new cable modem (CBR-T (CGA4131COM)) doesn't even respond to PD requests....