turning on comcast v6

ML ml at kenweb.org
Fri Dec 20 13:04:31 UTC 2013

On 12/20/2013 12:30 AM, Owen DeLong wrote:

>> I'd like to encourage people to use prefix-hint=::/48.
>> The router should accept the /60 and deal with it, but it's better to have Comcast's logs show that you requested a proper full-size prefix.
>> I'm almost afraid to ask about the phrase "add-default-route=yes" in the dhcp-client configuration. That seems wrong on the face of it since you should be getting your routing information from RA and not DHCP.

>From what I'm told "add-default-route=yes" is a hack by RouterOS
developers to add a default route via the link local address you receive
DHCP packets from.  This will break of course if DHCP server != intended
default gateway


>> In the case of Comcast (and anecdotally ISC DHCP) - You'll either need
>> to wait out the the lease time (4 days) or ask Comcast to nicely clear
>> out your /64 lease manually.  Release/renew doesn't release your current
>> DHCP lease.  I was getting A /64 and /60 (/64 had a preference of 255)
>> before Comcast removed the /64 lease manually.
> Is it somehow harmful to have both?
Yeah.. RouterOS doesn't install both prefixes into the IPv6 pool used
for assigning prefixes to your LAN interfaces. 

RouterOS is able to encapsulate sniffed packets into a TZSP container
and forward them to a host of your choice.  I was able to get a PCAP of
my DHCPv6 packets between Comcast and I.  There were two Advertise
packets from Comcast (/64 followed by /60) and RouterOS only replied
with (1) Request for the /64

More information about the NANOG mailing list