Find out dhcp assigned gateway and dns settings in Linux (CentOS)

Question

How to find the gateway and DNS IPs in a DHCP configured network in CentOS? I'm using CentOS installed in vmware using NAT connection and I want to make the ip static.

Solution 1

ifconfig

Will show the Interfaces, along with IP address. Normally, but not always eth0 will be the Interface you are looking for.

To find the DNS

cat /etc/resolv.conf

To find the gateway

route -n | grep "^0.0.0.0" | tr -s " " | cut -f2 -d" "

What you are saying about "wanting to make the IP static" scares me a bit. It would be wrong to take the dynamically assigned IP address and hard code it as a static as it will confuse the server. What you should do is either take another IP address in the same range - but one outside the range the DHCP server is assigning. An alternative is to modify the DHCP server to dynamically hand out static IP addresses if supported by your DNS server. If your DHCP server is ISC DHCP and you have access to do it, you can modify the config at /etc/dhcp3/dhcpd.conf with a bit like

   host hostname {
            hardware ethernet MAC.ADDR;
            fixed-address FIXED.IP.ADDR.HERE;                
    }

Solution 2

In CentOS 7 you can use nmcli d show to get the gateway and DNS addresses for all interfaces.

Comments

[Mohsenme]

Thanks. It seems you've misspelled ifconfig. I don't know why my resolv.conf was empty before. when I changed it turned back to dhcp again and restarted the network, it has the dns server now. I don't use ISC DHCP, is there a way to do it with the CentOS dhcp?

[davidgo]

Are you sure the CentOS dhcp is not the ISC one ? (It is for the servers I maintain, but you might be using something else like DNSMasq) You can possibly check it by running /usr/sbin/dhcpd --version

[Mohsenme]

Yes I see an empty /etc/dnsmasq.d directory but not /etc/dhcp3 directory.

[Mohsenme]

I finally found the dhcp settings under the host operating system at C:\ProgramData\Vmware\vmnetdhcp.conf