In terms of subscriber management, I understand there are two major approaches - DHCP and PPPoE.

I know I'm being very general, so give me some rope.

If using DHCP, RADIUS/AAA will authenticate the user, and then allow DHCP to happen, assign the address, etc. If I'm using PPPoE, the PPPoE session establishes, and the address is assigned via IPCP.

My question is, if I'm using PPPoE, can we use DHCP to assign the address? And if so, how is that address conveyed to the client? Will DHCP choose the address and be sent to the client via IPCP?

  • It's been decades since I worked with this stuff, but yes, some RAS can "proxy-DHCP" for the PPP endpoint, which gets the address as normal via IPCP. In theory, it's possible to send DHCP through a PPPoE tunnel, but why would you ever want to? – Ricky Jan 8 '16 at 4:34
  • Just a theoretical question, I wouldn't. ;) – Jordan Head Jan 8 '16 at 5:02
  • Just FYI, 'int dialer1' will allow 'ip address dhcp'. – Ricky Jan 8 '16 at 5:40

According to Cisco, you cannot use DHCP with PPPoE, :

PPPoE is not supported in conjunction with DHCP because with PPPoE the IP address is assigned by PPP.

Juniper has a whitepaper about Understanding PPPoE and DHCP:

The DSL Forum now also allows using IP over Ethernet (IPoE), which is based on DHCP. However, PPP remains the more mature and robust method for providing many broadband services

  • cisco.com/c/en/us/td/docs/ios-xml/ios/bbdsl/configuration/xe-3s/… Looks like they build a Virtual-Template and specify that it use a DHCP pool for addresses to assign them for PPPoE clients. – Jordan Head Jan 8 '16 at 2:25
  • Interesting that it is using ip unnumbered for the Virtual Template interface. For the IPv4, it is using an address pool, but that doesn't necessarily mean DHCP; notice that DHCP is not mentioned anywhere: Local Address Pool. The IPv6 does use DHCP, but it is really just prefix delegation. Neither has any interface with ip address dhcp or ipv6 address dhcp. – Ron Maupin Jan 8 '16 at 2:38

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