The problem you are having is that 300 is not a valid number. You must use 0 though 255 in each of the four "octets". Also, by using 10.100.200.# you are probably on a different network that your client device.
You need to take a look at what the ip address and subnet mask on your client machine is. This should let you know what a usable address on this network should look like.
Without going into a full TCP/IP class, if your subnet mask is 255.255.255.0 then the first three "octets" should match. For example:
Client IP address: 10.0.10.5
Client Subnet Mask: 255.255.255.0
The Server should have an IP address of 10.0.10.1 through 10.0.10.254, with a subnet mask of 255.255.255.0. You would also want to check your router to make sure you don't create an IP address conflict by assigning an address that's already been assigned.
Also, you said you changed the DNS address. Do you mean you changed the IP address? Or, did you actually change the DNS address? If you changed the DNS address, what was the previous IP address you accessed the server with? Try the "old" IP address when you ping and SSH, and let me know what your results were.