Deployment Guideline Summary

The following list summarizes deployment guidelines:

• Centralizing address translation makes keeping track of address assignment easier. Multiple NAT PEs might be required for load balancing. If this is the case, make sure public address pools do not overlap. One of the possible disadvantages to centralizing is the amount of redundancy that can be achieved by replication. For example, in a noncentralized environment, one gateway/server failure can result in an outage of only that VPN's service. However, in a centralized environment, a single gateway/shared PE failure can affect multiple VPNs. This drawback can be easily overcome by having multiple PEs that serve as shared gateways, which provide services to the same VPNs. So, you can provide redundancy with shared gateways.

• If VPNs that use overlapping private address space need to access a shared services segment, make sure that private address space is translated somewhere in the path.

• NAT impacts CPU utilization to a degree. Some protocols are more CPU-intensive than others. Therefore, the type of translation being performed could have significant performance impact. The impact is less for newer particle-based routers and more powerful routers.

• As the number of translation entries increases, the throughput in terms of packets per second (PPS) decreases. The effect is negligible for less than 10,000 translation table entries.

• The rate at which a router can add a new translation table entry decreases as the number of entries in the translation table increases.

• As the number of translation entries in the translation table increases, the amount of memory used increases.

Refer to Cisco Feature navigator for hardware and software support guidelines at the following website: http://tools.cisco.com/ITDIT/CFN/jsp/index.jsp.