Sometimes it can be helpful to have a friend work with you on the configuration, especially if they explain as they configure. Looking at the positive side of things, there is very little that you can do in configuring the switch that does real damage to the switch. There are a few serious things you might do (such as attempting to do a code upgrade in which you delete the existing image (without saving a copy) and loading an image file which is not appropriate for that hardware) but these are not likely. Almost any mistake you make in configuration can be corrected by doing a power cycle of the switch. The power cycle eliminates all the config changes you have made and puts you back at square one.
In one of your posts you ask what the various commands are doing. So here is an explanation:
- ip dhcp excluded-address defines addresses which will not be assigned dynamically by DHCP. The excluded addresses are configured manually on devices such as your switch, or your router, or some server (or other devices) which need static addresses. Any address in the DHCP pool that is not excluded can be assigned dynamically to a host on that segment of the network.
- ip dhcp pool LAN creates a pool for use in DHCP and gives it a name which is useful if you want to create more than one pool. With unique names you can have separate pools. The pool will have the addresses that are assigned by DHCP.
- network 192.168.20.0 255.255.255.0 defines the network addresses to be used in this pool. It also defines the mask to be used for this network. In assigning an address to a client DHCP tells the client what IP address to use and what mask to use.
- default-router defines what is the default gateway for clients in this segment. In assigning an address to a client DHCP also tells the client what is its default gateway. This is typically the router or layer 3 switch that is doing the layer 3 routing for this segment of the network.
These are three commands that are essential in configuring DHCP. You must create and name the pool, you must identify the network for the pool, and you must identify the default router. There are other commands that can be used. But with those three commands you can have working DHCP.
HTH
Rick
