jk's blog

Some Network Design Principles and Conventions

Different admins have different conventions. Here are a list of the ones I’m going to use:

I try to stick with the default values that appear on the hardware, so that the network can be “fixed” by resetting all the devices. By “fixed” I mean fixed enough to access the internet.

The gateway for each lan or vlan will be at ..*.254, and that will be the address of the router.

The services and printers are located at the low IP addresses, 1-64. The DHCP pool starts at 65. The network hardware, including switches, are at the top of the range, at 254 down to around 236.

The switches’ IP addresses will count down from 253, and each switch will have the same number in each subnetwork. So if the GS108T is at 253, then it will be,, etc.

At the very low numbers, reserve addresses for services that will have the same number on every segment. This way, you can use one server to provide services to multiple VLANs, and it won’t get that confusing. Skip using address ..*.1 because that’s the ZyXel default address for the gateway.

I am starting my network numbering at for vlan1, and changing 12, the third octet, to 13 for vlan2, etc.

I’m trying to skip using vlan2 and vlan3, because they are specified by default on the small Netgear switch.

The normal mode of the ZyXEL seems to be to route all non-broadcast traffic across all of its interfaces. So the vlans can access each other, and can access lan1.

Broadcast traffic is kept within a single vlan.

Vlan1 is the administration vlan, by default. I’m not going to change this.

Port 1 on the switch is always going to accept all traffic, and is set to vlan1, which is the administration vlan.

The last port is the vlans tagged port, aka a trunk in Cisco’s lingo. This port carries all traffic for all vlans. On the HP 1019, it’ll also be used as the stacking port. (The stacking port makes a “stack”, defined by HP as >1 switch that’s administered through one instance of the web-based gui.)

If you need a downlink port, then the second-to-last port should also be a tagged port. Unlike switches without vlans, you need to specify which ports carry all traffic.


When you first connect a switch into the network, before configuring vlans, the switch will request an IP address from lan1. When you assign vlans, the switch will then request an IP address from vlan1. The address will change. For sanity, I’m going to set the IP addresses of switches to numbers below

Rebooting any of these devices takes betwenn 30 seconds to a few minutes.

It’s useful to cut yourself some short ethernet cables ranging from around 7 inches to around 2 feet.

It’s useful to have at least two computers, maybe three.