Re: IPv6 Prefix Delegation to customers.

16 Jan 2020

      Brandon,

Juniper routers also snoop on via the built-in DHCP relay for the prefix delegation (PD).   The PD routes are inserted into the routing table as "access" routes with a next-hop of the WAN DHCP lease address for the CPE.  I normally configure all this in a BGP signaled L3VPN that automatically propagates these "access" routes to the routers through my MPLS network.  To link the PD pool of /48 prefixes to the right PE-CE access subnet, you create a shared-subnet in the DHCPv6 server that includes the /48 prefixes and the WAN prefix.

forwarding-options {
    dhcp-relay {
        dhcpv6 {
            overrides {
                allow-snooped-clients;
            }
            group group1 {
                active-server-group server-group1;
                relay-agent-interface-id {
                    use-option-82;
                }
                interface ae0.10;
            }
            server-group {
                server-group1 {
                   /* Central DHCPv6 servers */
                    2603:0:0:100::5;
                    2603:0:0:101::5;
                }
            }
        }
        forward-only;
        server-group {
            server-group1 {
                10.10.10.11;
                10.10.11.11;
            }
        }
        group group1 {
            active-server-group server-group1;
            overrides {
                allow-snooped-clients;
                layer2-unicast-replies;
                trust-option-82;
            }
           /* I only enable route-suppression of access routes for IPv4 */
            route-suppression {
                access-internal;
            }
            interface ae0.10;
        }
    }
}

-Steven

On 1/16/20, 11:00 AM, "NANOG on behalf of Jared Mauch" <nanog-bounces@nanog.org on behalf of jared@puck.nether.net> wrote:

    Arista/Cisco have commands like this:

    ipv6 dhcp relay install routes

    You place on the interface to make this happen.

    - Jared

    > On Jan 16, 2020, at 11:27 AM, Chris Gross <CGross@ninestarconnect.com> wrote:
    > 
    > In my environment I’ve been running Kea dhcp6 against Ciscos of varying platform (7600, ASR920, etc) and just them as a relay. In this case, the Cisco itself is installing a route as it snoops the relay action automatically. This was one of the harder things to wrap my head around before just slapping it in to see what happened and bam, routes. Router gets a WAN IP from the loopback via DHCPv6 as well, then gets PD assigned after.
    > 
    > interface Loopback10
    > vrf forwarding CGNAT
    > no ip address
    > ipv6 address 2001:DB8::1/64
    > !
    > interface VlanXXXX
    > vrf forwarding CGNAT
    > ip address 100.64.Y.Z 255.255.252.0
    > ip helper-address global 10.0.Y.Z
    > ip helper-address global 10.0.Y.Z
    > ip flow ingress
    > load-interval 30
    > ipv6 address FE80::1 link-local
    > ipv6 enable
    > ipv6 nd router-preference High
    > ipv6 dhcp relay destination 2001:DB8:0:A::BEEF source-address 2001:DB8:YZ01::1
    > ipv6 dhcp relay destination 2001:DB8:0:B::BEEF source-address 2001:DB8:YZ01::1
    > 
    > S   2001:DB8:YZ00:3F00::/56 [1/0]
    >      via FE80::4665:7FFF:FE14:EDC2, VlanXXXX
    >  
    > Chris Gross
    > Network Architect
    >  
    > From: NANOG <nanog-bounces@nanog.org> On Behalf Of Brandon Price
    > Sent: Wednesday, January 15, 2020 9:01 PM
    > To: nanog list <nanog@nanog.org>
    > Subject: IPv6 Prefix Delegation to customers.
    >  
    > CAUTION: This email originated from outside NineStar Connect. Do not click links or open attachments unless you recognize the sender and know that the content is safe. If you have any concerns, click here to open a ticket with the NetAdmin team.
    >  
    >  
    > Hey Nanog,
    >  
    > I am in the process of building out a FTTH proof of concept, and I would really like to offer each of my customers a /48 of IPv6.
    > I’ve been able to announce my /32 to my upstreams, dual-stack all of my internal infrastructure no-problem, build v6 recursive name servers, etc.
    > This was fairly straight-forward.
    >  
    > Where I am struggling is the Prefix Delegation part. How are most folks getting the PD subnets into their IGPs? In my environment I don’t run the DHCP server process on the router that is directly connected to the clients. I have seen documentation that cisco and juniper DHCPv6 processes are smart enough to insert that prefix into the routing table when they hand it out, but how is this handled in an environment with a central DHCP server? I do not currently run any PPPOE in my environment and I don’t use RADIUS for the subscriber management. I would really just like to stick to DHCP ideally.
    >  
    > If anyone has any pointers, I would appreciate it.
    >  
    > Brandon Price
    > Senior Network Engineer
    > City of Sherwood, Sherwood Broadband
    > Desk: 503.625.4258
    > Cell: 971.979.2182
    >  
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Re: IPv6 Prefix Delegation to customers.

Steven Karp