I guess one should detail the problem more intense:
There is indeed a network manager.But in case a static IP is given and the ,,start" button is pressed the device is shutdown and started anew, but this IP is not taken and therefore not in use.
Slitaz has been booted from the Live-CD. The problem occurs under ,,tux" as well as under ,,root".

I have written this note in http://doc.slitaz.org/en:guides:pxe?&#pxe-server-set-up

Since SliTaz 3.0 the Netbox application is splitted in Netbox and
Serverbox. If you are running a rescent SliTaz version, please read Serverbox application instead of Server tab below

Hmm...

must have missed that note.

As for the netbox problem:
Researching the netbox script I found that there are massive problems with the parameter expansion (single-quoted, double-quoted and 'escaped')
While in the 2.0 version of netbox (at least) the static IP part worked, with the change to functions within the 3.0 netbox script the parameter expansion happens to early.

I'll attach a 'diff' of what I changed to get (at least) the static IP to work.
Can't garantee the ppp, pptp, vpn stuff, but maybe somebody can pick up the thread and look into those parts.

Cheers,
OldGuy

Hmm..., how do I attach some additional information to this comment???
Edit1: Found it !! :-)
Edit2: Doesn't work! :-(

As the file attachment didn't work, here comes the diff as a comment.
If I broke any rules doing so, pls delete.

Part 1:

338,340c338,340
<                       <action>sed -i s/`cat /etc/network.conf | grep ^INTERFACE=`/INTERFACE="\$INTERFACE"/ /etc/network.conf</action>
<                       <action>sed -i s/DHCP="no"/DHCP="yes"/ /etc/network.conf</action>
<                       <action>sed -i s/STATIC="yes"/STATIC="no"/ /etc/network.conf</action>
---
>                       <action>sed -i s/^INTERFACE=.*/INTERFACE=\"\$INTERFACE\"/ /etc/network.conf</action>
>                       <action>sed -i s/^DHCP=.*/DHCP=\"yes\"/ /etc/network.conf</action>
>                       <action>sed -i s/^STATIC=.*/STATIC=\"no\"/ /etc/network.conf</action>
415,422c415,422
<                       <action>sed -i s/`cat /etc/network.conf | grep ^INTERFACE=`/INTERFACE="\$INTERFACE"/ /etc/network.conf</action>
<                       <action>sed -i s/DHCP="yes"/DHCP="no"/ /etc/network.conf</action>
<                       <action>sed -i s/WIFI="yes"/WIFI="no"/ /etc/network.conf</action>
<                       <action>sed -i s/STATIC="no"/STATIC="yes"/ /etc/network.conf</action>
<                       <action>sed -i s/`cat /etc/network.conf | grep ^IP=`/IP="\$IP"/ /etc/network.conf</action>
<                       <action>sed -i s/`cat /etc/network.conf | grep ^NETMASK=`/NETMASK="\$NETMASK"/ /etc/network.conf</action>
<                       <action>sed -i s/`cat /etc/network.conf | grep ^GATEWAY=`/GATEWAY="\$GATEWAY"/ /etc/network.conf</action>
<                       <action>sed -i s/`cat /etc/network.conf | grep ^DNS_SERVER=`/DNS_SERVER="\$DNS_SERVER"/ /etc/network.conf</action>
---
>                       <action>sed -i s/^INTERFACE=.*/INTERFACE=\"\$INTERFACE\"/ /etc/network.conf</action>
>                       <action>sed -i s/^DHCP=.*/DHCP=\"no\"/ /etc/network.conf</action>
>                       <action>sed -i s/^WIFI=.*/WIFI=\"no\"/ /etc/network.conf</action>
>                       <action>sed -i s/^STATIC=.*/STATIC=\"yes\"/ /etc/network.conf</action>
>                       <action>sed -i s/^IP=.*/IP=\"\$IP\"/ /etc/network.conf</action>
>                       <action>sed -i s/^NETMASK=.*/\NETMASK=\"\$NETMASK\"/ /etc/network.conf</action>
>                       <action>sed -i s/^GATEWAY=.*/\GATEWAY=\"\$GATEWAY\"/ /etc/network.conf</action>
>                       <action>sed -i s/^DNS_SERVER=.*/\DNS_SERVER=\"\$DNS_SERVER\"/ /etc/network.conf</action>

As the file is to long to be posted as a single comment, here comes part 2:
Pls concatenate befor use ;-)

Part2:

476c476
<                       <action>[ -n "\$NAME" ] && sed -i "s/^name .*/name \$NAME/" /etc/ppp/options</action>
---
>                       <action>[ -n "\$NAME" ] && sed -i s/^name .*/name \$NAME/ /etc/ppp/options</action>
486c486
<                       <action>[ -n "\$NAME" ] && sed -i "s/^name .*/name \$NAME/" /etc/ppp/options</action>
---
>                       <action>[ -n "\$NAME" ] && sed -i s/^name .*/name \$NAME/ /etc/ppp/options</action>
488,489c488,489
<                       <action>sed -i "s/DHCP=\"yes\"/DHCP=\"no\"/" /etc/network.conf</action>
<                       <action>sed -i "s/PPPOE=\"no\"/PPPOE=\"yes\"/" /etc/network.conf</action>
---
>                       <action>sed -i s/^DHCP=.*/DHCP=\"no\"/ /etc/network.conf</action>
>                       <action>sed -i s/^PPPOE=.*/PPPOE=\"yes\"/ /etc/network.conf</action>
495c495
<                       <action>sed -i "s/PPPOE=\"yes\"/PPPOE=\"no\"/" /etc/network.conf</action>
---
>                       <action>sed -i s/^PPPOE=.*/PPPOE=\"no\"/ /etc/network.conf</action>
544,546c544,546
<                       <action>[ -n "\$NAME" ] && sed -i "s/^ACCOUNT=.*/ACCOUNT=\$NAME/" /etc/ppp/scripts/ppp-on</action>
<                       <action>[ -n "\$PASS" ] && sed -i "s/^PASSWORD=.*/PASSWORD=\$PASS/" /etc/ppp/scripts/ppp-on</action>
<                       <action>[ -n "\$PHONE" ] && sed -i "s/^TELEPHONE=.*/TELEPHONE=\$PHONE/" /etc/ppp/scripts/ppp-on</action>
---
>                       <action>[ -n "\$NAME" ] && sed -i s/^ACCOUNT=.*/ACCOUNT=\$NAME/ /etc/ppp/scripts/ppp-on</action>
>                       <action>[ -n "\$PASS" ] && sed -i s/^PASSWORD=.*/PASSWORD=\$PASS/ /etc/ppp/scripts/ppp-on</action>
>                       <action>[ -n "\$PHONE" ] && sed -i s/^TELEPHONE=.*/TELEPHONE=\$PHONE/ /etc/ppp/scripts/ppp-on</action>
556c556
<                       <action>[ -n "\$NAME" ] && sed -i "s/^name .*/name \$NAME/" /etc/ppp/options</action>
---
>                       <action>[ -n "\$NAME" ] && sed -i s/^name .*/name \$NAME/ /etc/ppp/options</action>

Cheers,
OldGuy