Is PPPoE needed if a home DSL modem functions as a router?
I'm studying for my ISCW and would only see the need for this if the modem just bridges and no routing between the LAN\WAN side is involved
>> Is PPPoE needed if a home DSL modem functions as a router?
No, the client PC just gets a private IP address (RFC 1918) that is natted by the DSL router.
DSL router connection to ISP can be:
fixed public IP address : just IPv4 over ATM using aal5snap (typical for business offers)
PPPoA = PPP over ATM the DSL router will perform PPP negotation to get a public ip address using PPP over ATM (the address can change every time because it is taken from a pool).
For example my home router uses PPPoA.
There are also solutions using PPPoEoA with a DSL router but they are not needed (from a techical point of view, then a provider can choice to offer this type of access)
Some Business ADSLs we configure at work have simply IPv4 over ATM with a fixed ip address over an ATM PVC.
In general, in every country there are different solutions including PPPoE done over a LAN interface, usage or not usage of PPP authentication, usage or not usage of PPP IP address negotiation.
Hope to help