[c-nsp] DHCP_PD usage for PPPoE Access

[Miquel van Smoorenburg]

No, it's not saying "put a /64 on the WAN interface".

It says "put a /64 from the delegated prefix on a virtual interface".

And it says "if the WAN interface has no address and the router 
originates a packet, use the address of one of the other interfaces". 
Which will most likely be the aforementioned virtual interface.

So the effect is the same, but indeed, you should not use a /64 from the 
delegated prefix on the WAN interface directly.

Thanks for getting me to spell this out, I should really recheck what 
the implementation from our CPE vendor is doing ..

Mike.

On 26-03-11 12:11 AM, Frank Bulk wrote:
> I'm sorry, I don't follow how these excerpts from ipv6-cpe-router are
> recommending using a /64 out of the delegated prefix on the WAN interface.
>
> -----Original Message-----
> From: cisco-nsp-bounces at puck.nether.net
> [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Miquel van
> Smoorenburg
> Sent: Friday, March 25, 2011 4:52 PM
> To: cisco-nsp at puck.nether.net
> Subject: Re: [c-nsp] DHCP_PD usage for PPPoE Access
>
> http://potaroo.net/ietf/all-ids/draft-ietf-v6ops-ipv6-cpe-router-08.txt
>
>      WAA-8:  If the IPv6 CE router does not acquire global IPv6
>              address(es) from either SLAAC or DHCPv6, then it MUST create
>              global IPv6 address(es) from its delegated prefix(es) and
>              configure those on one of its internal virtual network
>              interfaces.
>
>      WAA-9:  As a router the IPv6 CE router MUST follow the weak host
>              model [RFC1122].  When originating packets out an interface
>              it will use a source address from another of its interfaces
>              if the outgoing interface does not have an address of
>              suitable scope.
>
> In short, put prefix::Y/64 on a loopback interface, then make the WAN
> interface ipv6 unnumbered loopback X (or something that has the same
> effect - in fact it should behave like that by default)
>
> Mike.
>
> On 25-03-11 10:03 PM, Frank Bulk wrote:
>> This approach was discouraged ipv6-ops listserv and one person pointed out
>> that this violates an RFC:
>> http://lists.cluenet.de/pipermail/ipv6-ops/2011-January/004677.html
>>
>> Frank
>>
>> -----Original Message-----
>> From: cisco-nsp-bounces at puck.nether.net
>> [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Victor Lyapunov
>> Sent: Thursday, March 24, 2011 10:30 AM
>> To: cisco-nsp at puck.nether.net
>> Subject: [c-nsp] DHCP_PD usage for PPPoE Access
>>
>> Hello
>>
>> I have been testing some scenarios for IPv6 over broadband
>> connections. The setup is a the most common one, the CPE gets
>>
>> -One ::/128 WAN ipv6 address using autonegotiaton.
>> -A signle ::/56 LAN subnet for the user networks, through DHCP-PD
>> (further subneted into /64 subnets for the various VLANs in the CPE)
>>
>> For this setup the NAS server is configured with a local ipv6 pool for
>> WAN address assignment (autonegotiation)
>>
>>     ipv6 local pool PPPOE 2001:100::/64 128 shared
>>
>> And a second pool used by the DHCP_PD
>>
>>    ipv6 local pool LAN 2001:200::/48 56
>>
>> In this way I have to maintain two different pools (one for CPEs WAN
>> and one LAN addressing).
>> A possible alternative that is discussed, is having the NAS allocate
>> just the DHCP_PD ::/56 prefix to the CPE (as far as global addresses
>> are concerned). And then configure the CPE to use the first of the
>> resulting 256 ::/64 subnets for the WAN and the rest for the LANs.
>>
>> What is your experience, is the second alternative worth pursuing? Is
>> there a common practice?
>>
>> Thanx for the input
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