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IPv6 Training (Cisco): What is Prefix Delegation? 
 


Added: 08/13/2008, Hits: 5,540, Rating: 0, Comments: 0, Votes: 0
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Well, to quickly answer your question; Prefix Delegation (PD) is considered to be a procedure (mechanism) that is used to automate the delegation of IPv6 prefixes (address blocks). Prefix Delegation is explained in RFC 3769 and is normally used by ISPs, to aid with the process of delegating IPv6 prefixes (address blocks) to their customers.

Ciscoís version of Prefix Delegation (PD) consists of three items a Customer Edge (CE) router, a Provider Edge (PE) router and a AAA server.

The Customer Edge (CE) router which is also known as the Requesting Router (RR) performs like a DHCP client and is located at the customerís premises; it has the job of requesting IPv6 prefixes (address blocks) from the Provider Edge (PE) router.

The Provider Edge (PE) router which is also known as the Delegating Router (DR) performs like a DHCP server and is located at the ISPís premises; it has the responsibilities of validating the authenticity and the profile of the Requesting Router (RR) with a AAA server; and also places a route into the ISPís routing system on the behalf of the Requesting Router (RR) for the delegated prefix.

The reason why the Delegating Router places a route into the ISPís routing system on the behalf of the Requesting Router (RR) for the delegated prefix; is to avoid the need for a dynamic routing protocol between the Delegating Router (DR) and the Requesting Router (RR). So, in other words, with Ciscoís version of Prefix Delegation the DR and RR are normally directly connected to one another; and only in certain circumstances its appropriate to configure a DHCP Relay router between the DR and RR to allow them to communicate.

Now, just in case if you were wondering; the AAA server that is connected to the DR at the ISPís location is the server that actually hands out the IPv6 prefixes and passes the IPv6 prefixes to the DR using Radius, so the DR can then pass the IPv6 prefix (address block) information to the RR.

I invite you to visit my website at www.ciscoipv6ittechtips.com
where youíll find the latest information regarding Cisco IPv6 Design and Implementation Techniques. And, also learn more about the new "Cisco IPv6 Video Accelerated Training Course" which contains over 3000 videos that will teach you all you need to know about Desiging, Building, and Deploying Cisco IPv6 networks. (Guaranteed)

To your success,

Charles Ross
CCNP #CSCO10444244
www.ciscoipv6ittechtips.com





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