Question on Ipv6 address

Wed Mar 27 02:34:02 UTC 2013

thanks for replies on the list, but still questions 

> 
> IPv6 is very different from IPv4.
> 
> In IPv6, there should be a /64 assigned to the point to point link over which a  /48 should be delegated to the customer.
> 
> If the customer doesn't have a router and is just attaching a single PC, he will not make the Prefix Delegation request and just the point-to-point /64 will be adequate.
> 
could we think about this as,   in a PPPoE access network,   /64 should be assigned to each access  vlan, and /48 should be prepared to delegated to a customer who uses  router to dials in with PPPoE link and have PCs connected to home router.  
In order to make full use of v6 address, could /56 be planned for delegated address?
> > 2. In dial-up network,  could each vlan's ipv6 link-id  be planned with its vlan number?     if so,  IP v6 address confliction could be avoided when  BAS is assigned a /64 or longer prefix.
> 
> Why would you ever assign a longer prefix?
> I'm not sure what you mean by "link-id", so I'm not sure what you are attempting to resolve here.
I means the host part of Ipv6 address.   
In Ipv4 network , we could identify each PPPoE session by IP address on BAS.   Each customer is assigned adifferent VLAN (Q-in-Q)
After introducing IPv6, we need  the same ability to identify each customer. as network prefix is assigned to PPPoE link,CPE's v6 address is composed by the prefix and interface part.   Besides self-calculating IPv6 address by CPE,  could weassign CPE special v6 address by   a  /128 prefix which is compose by a /64 prefix and a interface part  driving from Q-in-Qvlan numbers?

> 
> > 3. we are testing some BAS with IPv6 accessing, in radius accouting packets, there is     IP-v6-prefix, Ip-v6-link-id, Ip-v6-delegated-prefix.    how could dial-up PC's  IPv6    address be calculated with above information?
> 
> It probably can't. Why do you need to?
we need to identify each customer in network.
In ipv4 network,  each PPPoE customer has a fixed ip address which will be reported radius server by Framed-ip_address attributes.
In ipv6 environment,  radius accouting packets also contains  IP-v6-prefix 、Ip-v6-linkID (identify host part of v6 address)  and Ip-v6-delegated-prefix attributes.   to my understanding , if only a PC is connected to BAS,  IP-v6-prefix + IP-v6-linkID  could be used to identify PC's  IPv6 address. while if a router is connected,   BAS could only get delegated prefix and  PC behind home router could not be identified?

> 
> > 4. should it be necessary to plan  different IP-v6-prefix(IP-v6-delegated-prefix) for each dial-up customers  in BAS?
> 
> There are multiple ways to structure this.
> 
> If you put all of the customers into a common NBMA network, then you can use a single /64 prefix to number all of the link addresses from a given BAS to the customer sites. All of the CPE routers will use the same address on the BAS as their default gateway.
> 
> If you put the customers into individual VLANs, then each VLAN should have a /64 prefix assigned to it.
> 
> Beyond that, if the customer has a router, you should plan on having a /48 delegated prefix for each customer.
for cutomer has a router, should we plan a /64 prefix for PPPoE link and a /48 (or /56) prefix  delegeted to customers? After dials in ,     when a PC behind router access 6bone website. what address(or prefix) will be seen by web site it visits ? 

> 
> > 5. How could delegated IPv6 prefix be used in service provider's network? is this useful in dial-up access network?
> 
> The delegated prefix isn't used in the service provider's network. It is delegated to the customer for them to number their network. It can be used by the customer regardless of attachment method, though the low speeds of dialup make a complex topology on the far side less likely.
> 

best regards

Joe