error fetching interface information
 

when i start up my linux(redhat 6.1) computer, the NIC is brought up well:
Bringup interface eth0 [OK]
but after i login, ifconfig can only show:
lo Link encap: Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
UP LOOPBACK RUNNING MTU:3924 Metric:1
... ...
without any eth0 information.

i config the NIC by hand, ifconfig eth0 172.18.19.1 netmask 255.255.0.0, ok. eth0 works well, i can ping other computer with eth0. while if down it, error shows:
down: error fetching interface information: Device not found
it can not be down at all.

what's wrong with it, any suggestiong?

try to plumb it first.
#ifconfig eth0 plumb

Then try it again:
#ifconfig eth0 172.18.19.1 netmask 255.255.0.0 up
then down it and see if you get errors.

but i cannot plumb it at all.
#ifconfig eth0 plumb
plumb: Host name lookup failure
Usage:
ifconfig [-a] [-i] [-v] <interface> [[<AF>] <address>]
[add <address>[/<prefixlen>]]
[del <address>[/<prefixlen>]]
[[-]broadcast [<address>]] [[-]pointopoint [<address>]]
[netmask <address>] [dstaddr <address>] [tunnel <address>]
[outfill <NN>] [keepalive <NN>]
[hw <HW> <address>] [metric <NN>] [mtu <NN>]
[[-]trailers] [[-]arp] [[-]allmulti]
[multicast] [[-]promisc]
[mem_start <NN>] [io_addr <NN>] [irq <NN>] [media <type>]
[txqueuelen <NN>]
[[-]dynamic]
[up|down] ...

<HW>=Hardware Type.
List of possible hardware types:
loop (Local Loopback) slip (Serial Line IP) cslip (VJ Serial Line IP)
slip6 (6-bit Serial Line IP) cslip6 (VJ 6-bit Serial Line IP) adaptive (Adaptive Serial Line IP)
ether (Ethernet) tr (16/4 Mbps Token Ring) ax25 (AMPR AX.25)
netrom (AMPR NET/ROM) rose (AMPR ROSE) tunnel (IPIP Tunnel)
ppp (Point-to-Point Protocol) hdlc ((Cisco)-HDLC) lapb (LAPB)
arcnet (ARCnet) dlci (Frame Relay DLCI) frad (Frame Relay Access Device)
fddi (Fiber Distributed Data Interface) hippi (HIPPI) irda (IrLAP)
<AF>=Address family. Default: inet
List of possible address families:
unix (UNIX Domain) inet (DARPA Internet) ax25 (AMPR AX.25)
netrom (AMPR NET/ROM) rose (AMPR ROSE) ipx (Novell IPX)
ddp (Appletalk DDP)