My customer has an offsite network connected to their onsite network through a VPN. Both ends use private IPs. Now I want to implement a proxy/ISA server on the offsite network. Is it possible to implement with a single NIC or is using two NICs on a proxy/ISA server a must? If two NICs are to be used, then the NIC connecting to the router will be assigned with a public address and the NIC connecting to the local LAN will be assigned with a private address, right?
The point of an ISA server is to protect the network behind it, so you will want two NICs. It's not clear from your question what your current configuration looks like, but if the address on the LAN side of the router is public, then you will want a public address on the ISA server port that connects to the router and a private address on the LAN side.
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