|I forgot to address your questions directly, I'll try here:|
1. Could I make my Cisco 4000 enable DHCP, but only from a pool of addresses (ex: 10.10.150.240-250)
Certainly. Recently I had to setup a training lab with wireless. To avoid having too many users on a single AP I used two SOHO Routers with wireless capabilities. I split a pool of IP's between them. Something like the following:
Scope A = 192.168.1.100 to 192.168.1.150
Scope B = 192.168.1.151 to 192.168.1.200
The important thing is, if you're going to have two DHCP servers in the same segment of the same network, you want to ensure their scopes do not overlap so as to avoid any chance of duplicate IP's.
2. Would I make my Lynksis DHCP from a pool of addresses from 10.10.150.2-238?
As per above. If the two DHCP servers are on the same network, you do not want the pools overlapping. However, it shouldn't be necessary to have both router's providing DHCP if they ARE in the same network. A single DHCP server should be able to provide TCP/IP settings to any client requesting such. Click on my name above in one of my responses and read my "how-to" guide titled, "Add a Second Rtouer to your LAN". Pay attention to the scenario where you have only one subnet and connect the two routers "LAN port to LAN port" You'll notice I have DHCP disabled on the downstream router because cliients connected to it get their DHCP from the upstream router's DHCP server. The same theory applies in your case.............if the two routers are on the same network.
3. Should I consider subnetting?
I'd say no. Not unless you're out of IP addresses and absolutely have to.
4. FInally, what physical connections should I consider to connect the Cisco to our local network behind the firewall?
Since you want this all to be a single network, I'd say connect to the switch. If the rest of your network is setup as follows:
External Connections (x2) >> Dual WAN Router >> Switch >> AP's & Clients
then connecting the Cisco unit to the swtich incorporates it, and anybody connected to it, into the network.
You have the following:
Lynksis LAN= 10.10.150.0
Lynksis Router local IP= 10.10.150.1
Connect the Cisco to the switch, as per my guide, give it the following:
LAN IP = 10.10.150.2
DHCP Enabled = No
Clients connecting to the Cisco will still get DHCP settings from the Linksys and have full LAN access, including the VPN.
However, your setup is a little convoluted and I can't guarantee clients connecting remotely to the Cisco would get VPN access to the external site. This would of course require some testing and tweaking until it did work.
I still say the simplest solution is, remote clients VPN directly too external site bypassing your LAN altogether. This saves you some setup/testing and management headaches.......lol
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.