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Krellan

join:2001-06-06
Castro Valley, CA

3 edits

[IPv6] I received two blocks of IPv6 addresses?

I just got IPv6 from Comcast now! My router didn't pick up the IP address manually (will have to play with that a little) but upon connecting a Linux PC, and running the "rdisc6" command, it got two /64 blocks of IPv6 addresses!

What is the difference between these two blocks? Can one of them be used as a "routing subnet" for the other? If there's a FAQ somewhere already, please let me know about it.


NetFixer
Bah Humbug
Premium
join:2004-06-24
The Boro
Reviews:
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Re: SB6120 Firmware Updated (7/19/12)

said by Krellan:

Thanks!

I just got IPv6 from Comcast now! My router didn't pick up the IP address manually (will have to play with that a little) but upon connecting a Linux PC, and running the "rdisc6" command, it got two /64 blocks of IPv6 addresses!

What is the difference between these two blocks? Can one of them be used as a "routing subnet" for the other? I shouldn't hijack this long thread, so if there's a FAQ somewhere already, please let me know about it.

I don't know what to tell you about the double /64 IPv6 assignment on your Linux box. I don't see that, but then again I don't have Comcast's native IPv6 yet either (as mentioned in my previous post, I have to use the 6to4 tunnel).

You might want to open a new thread with that question; perhaps someone else has seen it (a thread in the »All Things Unix forum might be helpful too, if you don't get an answer here). OTOH, once you get your router configured for Comcast's IPV6, that symptom may disappear after the Linux box is behind the router (I am assuming that you saw the double /64 symptom with the Linux box directly connected to the cable modem).
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voiptalk

join:2010-04-10
Gainesville, VA

1 recommendation

reply to Krellan

Re: [IPv6] I received two blocks of IPv6 addresses?

I suspect you are seeing the WAN network and the LAN DHCP-PD assigned network.

Just from my own observation the WAN gets a 2001: network and the LAN a 2601: network.

What exactly are you seeing?

Xyc
Premium
join:2006-06-08
Sewell, NJ
reply to Krellan
Based on what I saw while doing some packet captures troubleshooting my DHCPv6-PD client I suspect what you're seeing is that you're being offered two addresses from two different DHCPv6 servers that the CMTS forwarded your solicit request to. Your client should pick one of the two advertisements (probably first to arrive) and request its prefix. The other server's advertisement should be ignored by your client unless the first server fails to complete the transaction and that second prefix eventually returned to the pool for other customers on your node.


whfsdude
Premium
join:2003-04-05
Washington, DC
reply to Krellan
More detail would be useful like voiptalk has pointed out, you're probably seeing the DHCPv6 address and then the IAPD address block.

DHCPv6 address should be a /128 though in 2001:0558::/29.

IAPD is a /64 out of 2601::/28.


NetDog
Premium,VIP
join:2002-03-04
Parker, CO
kudos:81
reply to Krellan
said by Krellan:

I just got IPv6 from Comcast now! My router didn't pick up the IP address manually (will have to play with that a little) but upon connecting a Linux PC, and running the "rdisc6" command, it got two /64 blocks of IPv6 addresses!

What is the difference between these two blocks? Can one of them be used as a "routing subnet" for the other? If there's a FAQ somewhere already, please let me know about it.

Can you tell us what blocks your seeing?