Networking

I don’t know about you, but I find myself forgetting the same things over and over, a case of déjà vu and amnesia at the same time: “I think I forgot this before!”  When it comes to networking configuration, small configuration errors happen most frequently. Here is a checklist of my most encountered networking configuration errors and what I am doing to reduce the chances of them happening again.

1. Subnets other than 24-bit: How many subnets do you have that are something other than a 24-bit netmask (255.255.255.0)? I don’t work with many subnets other than the standard class C network, but every time I do, I have to double-check myself to make sure the correct subnet mask is applied. I’m trying to find reasons to use subnets other than the venerable 24-bit mask, but the reasoning becomes uncertain in most internal IP address spaces with non-routable IP addresses.
2. DNS suffix lists: Having a complicated list of DNS suffixes and missing one or more of the entries can make name resolution a little less than pleasant. The good news is that we can fix this via Windows Group Policy to set a primary suffix and suffix search-order for each computer account.
3. Default gateway other than .1: Each time a static IP address is configured on a network that has a default gateway other than .1, I get a little confused and have to double-check the configuration. For subnets smaller than 255 hosts (a class C subnet), the chances are higher that the last octet of the IP address space will not permit a .1 default gateway. The fix can be to standardize on class C subnets for internal networks, even if there are wasted IP addresses at the end of the range.
4. DNS IP addresses: If I had it my way, every DNS server at every site would have the same IP address structure of every other site. That way, I would only have to determine the first two or three positions of the IP address and the DNS servers would be easy to determine. Anything that I can do to standardize, I am game for. For example, if every network has a .1 default gateway .2 can be the DNS server for that network. That, I can remember.
5. WINS in all of its glory: I can ping the server by fully qualified domain name, but can’t access just the NetBIOS name. A number of things can be wrong including WINS configuration. Frequently, a properly configured set of DNS suffixes and search orders can address this. But, one way to avoid the issue is to implement the globalnames zone with Windows Server 2008’s DNS engine.

These are the little things in networking that get me more frequently that I’d like. What little things get in the way for your networking administration? More importantly, what tips do you have to avoid them from a repeat appearance on your irritation list?