Can't get Centos to talk to anything!

Issues related to configuring your network
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Posts: 2
Joined: 2007/03/01 05:16:28

Can't get Centos to talk to anything!

Post by RobB » 2007/03/01 05:40:59

I have recently built a Centos 4.4 server, it's fine except it won't network. During boot if fails to find my DHCP server, if I nail the IP, subnet mask and default gateway, if does not fail but reports "network unreachable". The routing table seems to be full of rubbish even though I have not done anything with it. Also I seem to have IP6 enabled and I can't turn it off.

I have done a complete reinstall and it's exactly the same. I downloaded the install from the UK Warwick mirror site.

Pinging the loopback works fine, and the card can (if i set the IP address) ping it's own IP with or without a network cable attached.

I have replaced my switch with a hub, and tried more than one cable. If I replace my Centos HDA with a XP boot HDA the network card works fine.

Some info:

# ps -ef|grep 'net'

root 3225 1 07:57 ? 00:00:00 xinetd -stayalive -pidfile /var/run/

# ps -ef|grep 'portmap'

rpc 2991 1 ? 07:57 00:00:00 portmap

Some info from ifconfig (I have lost the MAC address somehow during copy, there is one honest):

eth0 Link encap:Ethernet HWaddr:
inet addr: Bcast: Mask:
inet6 addr: fe80::202:e3ff:fe14:7242/64 Scope:Link
RX packets:0 errors:0 dropped:416 overruns:0 frame:0
TX packets:16 errors:0 dropped:3 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 b) TX bytes:896 (896.0 b)
Interrupt:11 Base address:0x8000

lo Link encap:Local Loopback
inet addr: Mask:
inet6 addr: ::1/128 Scope:Host
RX packets:2196 errors:0 dropped:0 overruns:0 frame:0
TX packets:2196 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:2670540 (2.5 MiB) TX bytes:2670540 (2.5 MiB)

Some info from lspi:

00:06.0 Ethernet controller: National Semiconductor Corporation DP83815
(MacPhyter) Ethernet Controller

Some info from lspi -vv:

00:06.0 Ethernet controller: National Semiconductor Corporation DP83815
(MacPhyter) Ethernet Controller
Subsystem: Netgear FA311 / FA312 (FA311 with WoL HW)
Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B-
Status: Cap+ 66Mhz- UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- SERR- <PERR-
Latency: 32 (2750ns min, 13000ns max)
Interrupt: pin A routed to IRQ 11
Region 0: I/O ports at a000 [size=256]
Region 1: Memory at e7000000 (32-bit, non-prefetchable) [size=4K]
Capabilities: [40] Power Management version 2
Flags: PMEClk- DSI- D1+ D2+ AuxCurrent=320mA PME(D0+,D1+,D2+,D3hot+,D3cold+)
Status: D0 PME-Enable- DSel=0 DScale=0 PME+

info from modprobe:

# modprobe -l natsemi


info from lsmod:

# lsmod | grep natsemi

natsemi 30497 0

My DHCP server is at, my subnet mask is, default gateway is the same as the DHCP server at The DHCP server also acts ad a NAT firewall out to the internet.

When I nail the IP I use as it is outside my DHCP range, I can ping nothing on my net, and the Centos server does not respond to ping from any other machine. The network card I am using does not support the ability to change it's MAC address.

Any help much appreciated.


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Joined: 2005/11/29 02:35:25
Location: Indiana

Can't get Centos to talk to anything!

Post by Lenard » 2007/03/01 11:31:01

Some things to check with example outputs:

$ cat /etc/sysconfig/network-scripts/ifcfg-eth0
# Please read /usr/share/doc/initscripts-*/sysconfig.txt
# for the documentation of these parameters.

$ cat /etc/sysconfig/network

$ sudo cat /etc/sysconfig/iptables
# Firewall configuration written by system-config-securitylevel
# Manual customization of this file is not recommended.
:RH-Firewall-1-INPUT - [0:0]
-A INPUT -j RH-Firewall-1-INPUT
-A FORWARD -j RH-Firewall-1-INPUT
-A RH-Firewall-1-INPUT -i lo -j ACCEPT
-A RH-Firewall-1-INPUT -p icmp --icmp-type any -j ACCEPT
-A RH-Firewall-1-INPUT -p 50 -j ACCEPT
-A RH-Firewall-1-INPUT -p udp --dport 5353 -d -j ACCEPT
-A RH-Firewall-1-INPUT -p udp -m udp --dport 631 -j ACCEPT
-A RH-Firewall-1-INPUT -p tcp -m tcp --dport 631 -j ACCEPT
-A RH-Firewall-1-INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
-A RH-Firewall-1-INPUT -m state --state NEW -m tcp -p tcp --dport 22 -j ACCEPT
-A RH-Firewall-1-INPUT -j REJECT --reject-with icmp-host-prohibited

Also verify that the /etc/modprobe.conf file has a line entry like: alias eth0 natsemi

Posts: 2
Joined: 2007/03/01 05:16:28

Re: Can't get Centos to talk to anything!

Post by RobB » 2007/03/01 19:03:45

Great, thanks for the pointers, unfortunately it will be the weekend brfore i get to have a look at this due to work commitments.

I'll let you know how I get on.


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