Tom Rauschenbach wrote:
>
> I've been unsuccessful using etherreal to capture the initial DHCP negotions on
> the interface ppp0.
That's a bit of a chicken and egg problem since pppd and the kernel
conspire to bring pppX interfaces into existence.
IPCP (the IP Control Protocol) is used to set up IP addresses for each
side of the link (plus there's the M$ hack that also passes along name
server addresses during IPCP as well...) This occurs after LCP (Link
Control Protocol) has negotiated the link parameters...
Your best bet until ppp0 is up and running is to use pppd's "debug"
option, and look at the log file. It'll give you a pretty good idea
of what's working and what's not during those handshakes.
Anyway the initial flow of a PPP connection is:
Possibly talk to some gizmo via a "chat" script, to "log in". This
has to pass muster first before PPP will try to start...
LCP: each side trades info regarding link characteristics/restrictions (8-bit
clean or not, MTU size [typcially 1500 bytes but can be smaller],
characters that get swallowed by the link, and sometimes what
upper-layer protocols need to be negotiated e.g. authentication.)
PAP/CHAP: optional password authentication, if there's no login script
required
CCP: Negotiation for a packet data compressor. M$ I believe uses Shiva
or a proprietary protocol. This is also optional.
IPCP: IP address negotiation, and again through a M$ hack name server
addresses may be sent along as well.
At a minumum LCP and IPCP need to come up, in that order, for a working
PPP link to be established. (I'm ignoring for a moment that other networking
protocols besides IP can be established over PPP...)
-- Farrell
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