Server all of a sudden can't access the net

[Man-O-Leisure]

Hey, i have a Centos 5.5 server, which i have been using whilst setting it all up at my home, connecting to the internet without any problems until now.. All of a sudden it can't access the net, it can't ping my router.. but i am able to VNC to it accross the network, passing through said router.

I have it set up with a static IP, and the router IP put in as DNS and gateway, when i tell it to get an IP vi DHCP, still the same problem.. I have no idea how to get this working, any ideas?? I am new with Linux, so please exlain what i need to do..

The only thing running on this server is basically Freeradius2, Coovachilli, Webmin and a virtual machine, which is an iRedOS Mail server.

Thanks guys

[Man-O-Leisure]

Wow.. no one has any idea?

[Man-O-Leisure]

Adding to this, when try and set the Network adapter to get IP via DHCP, it tries to restart the network adapter but always fails..

In windows i would reset the TCP Stack, but have no idea how to reset all networking in Linux, and it seems no one else on this forum knows how to either??

I really would apreciate a response...

[MikeTbob]

Did you get a kernel update? This will usually mean that you need to re-install the drivers.

[Man-O-Leisure]

Hey, no updates. Just working one day, not the next.. When you say drivers do you mean for the NIC? Cause its working fine, i can SSH and VNC to the box accross the network

[Rubberman]

Have you tried resetting/rebooting the router? Perhaps its DNS cache is fubar. If that doesn't work, then you can tell your network manager (or manually add to /etc/resolv.conf) to use external DNS servers. Add either (or both) of these to /etc/resolv.conf and then try accessing the internet. They are top-level DNS servers at bellatlantic.net:

nameserver 199.45.32.37
nameserver 199.45.32.40

They have been useful for me in the past when I had dns server or router problems, like when my normal ISP's servers were fubar. Since your router gets its DNS information from your ISP, if their server is having problems, this would explain your symptoms.

[Man-O-Leisure]

Hey thanks for that. I had infact reset my router, but there must still be something up, whether it be dns on the router or server, cause i just realised i am unable to ping my router, but i was able to ping those 2 nameservers you gave me...

I need to setup DNS on my server and have no idea how to.. but in the meantime, i guess i can get online by taking out the 192.168.1.1 nameserver in the /etc/resolv.conf file and putting in those of my ISP nameservers?

[Rubberman]

Well, you can directly edit /etc/resolv.conf and add the DNS server entries you want there, though some systems will regenerate the resolv.conf file on reboot. If it does that, then you can edit /etc/sysconfig/network-scripts/ifcfg-eth0 (or eth1, etc) and add the DNS entries there. Here is an example of mine:

DEVICE="eth0"
NM_CONTROLLED="yes"
ONBOOT=yes
TYPE=Ethernet
BOOTPROTO=none
DEFROUTE=yes
IPV4_FAILURE_FATAL=yes
IPV6INIT=no
NAME="System eth0"
UUID=5fb06bd0-0bb0-7ffb-45f1-d6edd65f3e03
HWADDR=00:15:17:41:61:F8
IPADDR=192.168.1.20
PREFIX=24
GATEWAY=192.168.1.254
DNS1=68.94.156.1
DNS2=68.94.157.1
DNS3=192.168.1.254

Whatever you do, don't change the UUID and HW address fields in your own file... Just edit the GATEWAY and DNS entries - you can add more DNS server addresses here if you want (DNS4, DNS5, etc).

[Man-O-Leisure]

Thanks for this. I have just been able to get online on teh server thanks to your precious post. I changed the nameserver in the /etc/resolv.conf file to my ISP's DNS servers. I will now try this last bit that you have sent me.

My plans are to setup DHCP and DNS on this server, and squid for caching. if you have any idea where i can learn how to do that i would be even more happy!

I just want DHCP for the machines in my office, and squid caching for external clients, we have a small WISP, the wireless clients get their DHCP from our wireless router and would like to have a squid caching server on this centos box, so that loading of regularly used sites is fast. Know what i mean?

I am a Windows server admin, trying to get all this working in Linux as i know it is the safest, stablest setup we can have. Unfortunately, i dont really know what i m doing with Linux..

Thanks mate.