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I am using Windows 7. Here is a correct ipconfig which helps me connect to Internet:

IPv4 Address 192.168.1.100
Subnet Mask 255.255.255.0
Default Gateway 192.168.1.254

It happens so often that in the morning when I first turn on my computer, the Default Gateway was assigned as 192.168.1.252 so I could not connect to Internet and had to set a static Default Gateway myself.

There are two IPs that my default gateway is randomly assigned:

192.168.1.254 (correct)
192.168.1.252 (incorrect)

I don't know where the value of 192.168.1.252 comes from. I can not ping 192.168.1.252. I checked on my router setup page (192.168.1.254) but could not find any proof.

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closed as off-topic by Jenny D, Iain, MichelZ, HopelessN00b, Rex Apr 18 at 14:30

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1  
You should consult with your system administrator. This is probably a DHCP issue / multiple DHCP issue –  MichelZ Apr 18 at 8:24
    
Unfortunately, I am taking the role as a system administrator now and still don't know where is the second DHCP server. –  trogerx Apr 18 at 8:41
    
If you get .252 again, have a look at ipconfig /all, it will list you the IP Address of the DHCP Server where the settings came from –  MichelZ Apr 18 at 8:46
    
Using ipconfig /all I found out that the second DHCP server is on a Win 2008 server machine, turn this DHCP server off and I solved the issue, thanks. –  trogerx Apr 18 at 9:21

2 Answers 2

up vote 1 down vote accepted

Also because we don't know anything about your network and if we assume that it's big LAN it's possible that there is seccond DHCP server in network (even with the same IP as right DHCP so you won't figure it out) and give IP address to you faster than right DHCP server. Network administrator can easily find second DHCP server in LAN using dhcpdump (linux software).

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I am trying to find the second DHCP server now, thanks. –  trogerx Apr 18 at 8:41
1  
You wrote that you get IP from 192.168.1.254. If your default gateway 192.168.1.254 is also DHCP Server and it's configured to set cliets gateway to 192.168.1.254 and still your clients get from 192.168.1.254 default gateway 192.168.1.252 you should just change (for a test period) your DHCP Server IP from 192.168.1.254 to some other IP and try to ping 192.168.1.254. If it replies check it's MAC with command arp -a and you have seccond DHCP mac. Change your DHCP server IP back to 192.168.1.254. Find mac of seccond DHCP on switches and turn this port down. –  vonom Apr 18 at 8:44

Did you check your router DHCP settings ? DHCP is responsible for giving you your IP address and also your gateway.

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I can see on my router config page: DHCP Gateway: 192.168.1.254 –  trogerx Apr 18 at 8:12

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