Follow this:
Install Networkcard Driver
http://www.slitaz.org/en/doc/handbook/network-config.html

Does your network adapter connect to USB ?
Install usbutils libusb and libusb-compat tazpkg's
Use lsusb instead of lspci command in tutorial

Tx for the reply,
It is not USB. It is a ethernet card (eth0) which connects to a powerline plug (CPL in French).
I checked the Handbook, already. However, it does not tell much as far as the DHCP tab (where the config takes place ?).
The powerline plug works fine (I have used it today with a laptop running another flavor of linux).

I'll give you some commands done in xterm as root from my computer so you can see what the results would look like.

root@slitaz:~# udhcpc
udhcpc (v1.12.0) started
Sending discover...
Sending select for 192.168.123.9...
Lease of 192.168.123.9 obtained, lease time 604800
deleting routers
route: SIOCDELRT: No such process
adding dns 209.18.47.61
adding dns 209.18.47.62

udhcpc is the dhcp client slitaz uses to query the dhcp server in my router which then leased my network adapter the lan address of 192.168.123.9 and passes on the domain name server addresses from my isp

root@slitaz:~# ifconfig
eth0      Link encap:Ethernet  HWaddr 00:24:1D:23:A1:DB  
          inet addr:192.168.123.9  Bcast:192.168.123.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:193 errors:0 dropped:0 overruns:0 frame:0
          TX packets:228 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:83345 (81.3 KiB)  TX bytes:41739 (40.7 KiB)
          Interrupt:17 Base address:0xc000 

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

ifconfig confirms my network adapter is eth0 and is assigned ip address 192.168.123.9

root@slitaz:~# route
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
127.0.0.1       *               255.255.255.255 UH    0      0        0 lo
192.168.123.0   *               255.255.255.0   U     0      0        0 eth0
default         192.168.123.254 0.0.0.0         UG    0      0        0 eth0

route indicates 192.168.123.254 is the default gateway address to the internet which is the lan side of my router

root@slitaz:~# ping 192.168.123.254
PING 192.168.123.254 (192.168.123.254): 56 data bytes
64 bytes from 192.168.123.254: seq=0 ttl=64 time=1.175 ms
64 bytes from 192.168.123.254: seq=1 ttl=64 time=1.162 ms
64 bytes from 192.168.123.254: seq=2 ttl=64 time=1.166 ms
64 bytes from 192.168.123.254: seq=3 ttl=64 time=1.165 ms
^C
--- 192.168.123.254 ping statistics ---
4 packets transmitted, 4 packets received, 0% packet loss
round-trip min/avg/max = 1.162/1.167/1.175 ms

ping from slitaz to my gateway verifys connectivity within my lan

root@slitaz:~# ping www.yahoo.com
PING www.yahoo.com (67.195.160.76): 56 data bytes
64 bytes from 67.195.160.76: seq=0 ttl=53 time=37.102 ms
64 bytes from 67.195.160.76: seq=1 ttl=53 time=36.755 ms
64 bytes from 67.195.160.76: seq=2 ttl=53 time=43.701 ms
64 bytes from 67.195.160.76: seq=3 ttl=53 time=41.135 ms
64 bytes from 67.195.160.76: seq=4 ttl=53 time=41.600 ms
^C
--- www.yahoo.com ping statistics ---
5 packets transmitted, 5 packets received, 0% packet loss
round-trip min/avg/max = 36.755/40.058/43.701 ms

ping from slitaz to www.yahoo.com verifys connectivity to internet and dns resolution is working