sbc dsl and linksys firewall config issues

[Gerald Combs]

Jonathan Hutchins wrote:
> On Saturday 15 January 2005 05:35 pm, hanasaki wrote:
> 
> 
>>= scenario 1 =
>>linksys to the dsl modem with the modem doing the ppoe auth.
>>modem gets an IP from dsl
>>linksys gets an IP from modem
>>pc gets an IP linksys
>>can not get from the pc to the Internet
> 
> 
> Right.  Double NAT doesn't usually work.

Why wouldn't it?  I'm doing this here at home simply because I haven't
bothered to turn NAT off on my access point (which is behind my main
firewall).  Double-NATted connectivity works fine, including
NAT-unfriendly stuff like PPTP and IPSec.

>>= scenario 2 =
>>linksys to the dsl modem with the modem being a bridge
>>linksys doing the ppoe auth.
>>linksys ppoe auth works and linksys gets an IP from dsl
>>pc gets an IP linksys
> 
> 
> That's how you're supposed to do it.
> 
> 
>>browse most sites ok but seems to be slow to connect
>>seems to be lower bandwidth
>>some sites (hotmail/ebay) timeout
> 
> 
> PPPoE.  Lousy system.  SBC DSL - what did you expect?
> 
> 
>>same sites work if accessed as in scenario 1

In each scenario, what addresses get assigned to each link, and what MTU
is in use on each link?  Does scenario 2 work if you set your PC's MTU
to match the PPPoE link (probably 1480)?