DSL modem question

Answered Question
Aug 11th, 2008
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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!

Correct Answer by Giuseppe Larosa about 8 years 10 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
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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
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Thanks, this helps clear up the how\why of the various methodologies!

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