I have a customer where we are deploying Cisco IPT with Cisco 2821 Voice Gateway. The customer has a separate Linksys based Internet router for the Internet users.
I am going to have to connect Cisco 2821 Ethernet port to the Linksys router in order for my (3) IPT servers with static IP Addresses (behind Cisco 2821 Router) to go out to the Internet for AntiVirus signature update.
I can build a layer III access-list on my 2821 router to allow only (3) IPT servers to be able to access the Internet via Linksys router.
The problem is that customer wouldn't allow any static IP address on my Ethernet port of 2821 that will connect to Linksys router, and we are forced to go with dynamic IP Address that the Cisco 2821 will learn from Linksys router for its Ethernet Port. In other words, Cisco 2821 will act as a DHCP Client to receive the IP address from the private Pool addresses configured in Linksys router.
Will I still be able to configure a layer III access-list on my 2821 Ethernet Port since the port doesn't have an static IP address, and the IP address may get changed if lease expires.
Should I go with Layer II access-list where I can restrict traffic based on Server's MAC addresses.