The limitation will probably be memory and there isn't any way to know for sure without testing. One of the Cisco folks here may know approximately how many bytes of memory a NAT entry uses, but this will be good for only rough estimations at best.
I believe that would depend on the level/type of translation you're going to use.
For example, High CPU utilization caused by IP Input:
"IP Network Address Translation (NAT) is configured on the router and there are lots of Domain Name System (DNS) packets going through the router. UDP or TCP packets with source and/or destination port 53 (DNS) are always punted to process level by NAT."
But with Cisco IOS 12.3, you can use the NAT Rate-Limiting feature:
[toc:faq]The ProblemOn traditional switches whenever we have a trunk
interface we use the VLAN tag to demultiplex the VLANs. The switch needs
to determine which MAC Address table to look in for a forwarding
decision. To do this we require the switch to do...
[toc:faq]Introduction:Netdr is a tool available on a RSP720, Sup720 or
Sup32 that allows one to capture packets on the RP or SP inband. The
netdr command can be used to capture both Tx and Rx packets in the
software switching path. This is not a substitut...
IntroductionOSPF, being a link-state protocol, allows for every router
in the network to know of every link and OSPF speaker in the entire
network. From this picture each router independently runs the Shortest
Path First (SPF) algorithm to determine the b...