DSL modem question

Answered Question
Aug 11th, 2008

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

Thanks!

I have this problem too.
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Correct Answer by Giuseppe Larosa about 8 years 4 months ago

Hello Joshua,

>> 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

Giuseppe

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Correct Answer
Giuseppe Larosa Mon, 08/11/2008 - 10:42

Hello Joshua,

>> 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

Giuseppe

gojericho0 Mon, 08/11/2008 - 10:50

Thanks, this helps clear up the how\why of the various methodologies!

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