iptables - specifying iface that does not currently exist

Hi,

I've set up a router and firewall with iptables, the external link is a
ppp one using the speedtouch USB modem and the internal is a normal
ethernet card. The ppp link isn't always up, pppd will repeatedly try
until it gets through.

My question is: when the ppp0 iface goes down, what happens to the data
packets being forwarded out from the LAN to the internet? I have
ip_forward and ip_dynaddr both set to 1 and I know it's perfectly legal
to specify with iptables an iface that does not exist. But something
must be done to the packets being continuously sent into tho router
destined into a downed iface... Does the kernel buffer them up until
the link is back up (ip_dynaddr = 1)? wouldn't there be a limit for
this buffering? Should I turn off just the ip_forward and firewall with
the ip-down hook or is this unnecessary?

I need this router to be rock solid, with minimum maintainence as I
won't be able to administer it easily. hopefully someone can help me
out on this detail which I can't find any info on.

Cheers for any help received!

Justin

.

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