pppd

man pppd :)

/etc/ppp/auth-up
A program or script which is executed after the remote system successfully authenticates itself. It is executed with the parameters
interface-name peer-name user-name tty-device speed
Note that this script is not executed if the peer doesn't authenticate itself, for example when the noauth option is used.
/etc/ppp/auth-down
A program or script which is executed when the link goes down, if /etc/ppp/auth-up was previously executed. It is executed in the same manner with the same parameters as /etc/ppp/auth-up.
/etc/ppp/ip-up
A program or script which is executed when the link is available for sending and receiving IP packets (that is, IPCP has come up). It is executed with the parameters
interface-name tty-device speed local-IP-address remote-IP-address ipparam
/etc/ppp/ip-down
A program or script which is executed when the link is no longer available for sending and receiving IP packets. This script can be used for undoing the effects of the /etc/ppp/ip-up script. It is invoked in the same manner and with the same parameters as the ip-up script.

тебе ip-down видимо нада

> ip-down видимо нада

Вряд ли :) ip-down запускается, когда соединения уже нет, а ему надо, когда ещё есть, то есть, непосредственно перед выдёргиванием шнурка модема из телефонной розетки :)

Верно, как я и написал в посте, ip-down выполняется уже после того, как закрывается интерфейс ppp0