i run linux from a live cd and i have no internet connection. when i try to ping my modem i get the messege : connect: network is unreachable.
and when i try this :
route add default gw "ip address of getaway"
then i get the messege : SIOCADDRT: no such process

please give me informatio about how to connect internet in fedora

Which distro do you use ?
Which chipset do you use ?
Is Adsl or dial up ?

i use the disrto back track 3 final and it is adsl. where can i find which chipset i'm using?

lspci command in a terminal. You may need to be root to run it.

when i type the lspci command i get this :

00:00.0 Host bridge: Intel Corporation 82945G/GZ/P/PL Memory Controller Hub (rev 02)
00:01.0 PCI bridge: Intel Corporation 82945G/GZ/P/PL PCI Express Root Port (rev 02)
00:1b.0 Audio device: Intel Corporation 82801G (ICH7 Family) High Definition Audio Controller (rev 01)
00:1d.0 USB Controller: Intel Corporation 82801G (ICH7 Family) USB UHCI Controller #1 (rev 01)
00:1d.1 USB Controller: Intel Corporation 82801G (ICH7 Family) USB UHCI Controller #2 (rev 01)
00:1d.2 USB Controller: Intel Corporation 82801G (ICH7 Family) USB UHCI Controller #3 (rev 01)
00:1d.3 USB Controller: Intel Corporation 82801G (ICH7 Family) USB UHCI Controller #4 (rev 01)
00:1d.7 USB Controller: Intel Corporation 82801G (ICH7 Family) USB2 EHCI Controller (rev 01)
00:1e.0 PCI bridge: Intel Corporation 82801 PCI Bridge (rev e1)
00:1f.0 ISA bridge: Intel Corporation 82801GH (ICH7DH) LPC Interface Bridge (rev 01)
00:1f.1 IDE interface: Intel Corporation 82801G (ICH7 Family) IDE Controller (rev 01)
00:1f.2 RAID bus controller: Intel Corporation 82801GR/GH (ICH7 Family) SATA RAID Controller (rev 01)
00:1f.3 SMBus: Intel Corporation 82801G (ICH7 Family) SMBus Controller (rev 01)
01:00.0 VGA compatible controller: ATI Technologies Inc Radeon X1650 XT (Primary) (PCIE) (rev 9a)
01:00.1 Display controller: ATI Technologies Inc Radeon X1650 XT (Secondary) (PCIE) (rev 9a)
02:01.0 FireWire (IEEE 1394): Agere Systems FW323 (rev 70)
02:03.0 Ethernet controller: Atheros Communications Inc. AR5413 802.11abg NIC (rev 01)
02:08.0 Ethernet controller: Intel Corporation 82801G (ICH7 Family) LAN Controller (rev 01)

Do you use a static ip address or DHCP?

Is it possible in you,re distro to find out if it do recognize you,re LAN card and that it use the proper driver
It is a on board LAN card is it not ?
I prefer Lan card in a PCI slot.

i use DHCP

does "ifconfig eth0" pull an appropritate IP address and default gateway?

it says :
eth0: error fetching interface information: device not found

Thats strange considering the last line of your ifconfig below shows an ethernet device.

-------------------------------------------
02:08.0 Ethernet controller: Intel Corporation 82801G (ICH7 Family) LAN Controller (rev 01)
-------------------------------------------

Do you get an ip address on another interface if you just do "ifconfig"?

output of ifconfig

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)

Judging from the codes 82801G in the line of the Intel Ethernet Controller and 802.11abg in the line for the Atheros NIC, I'm guessing you're using a Wireless device, right?
Perhaps the wlan device is disabled?

no i'm not using a wireless device and i also don't use wlan.