Your question is not clear whether you intend to do clear text authentication or to do MD5 authentication. I believe that any kind of authentication will create some amount of extra work for the CPU with MD5 requiring more processor effort than clear text. Attempting to predict how much increase in CPU would depend on how much traffic is being authenticated (how many neighbors generating how many hello messages, how many LSAs must be processed, and how frequently are LSAs received reflecting changes in the network.
I do not believe that authentication will generate a large increase in CPU processing, but I believe that there will be some increase.
Sure this will increase the CPU usage than normal utilization, but how much the CPU will reach this is depending on the current CPU utilization of your gear and how many OSPF neighbors will be authenticated for example if you are gone secure the OSPF neighbor ship between your PE router and 100 OSPF CE neighbors this is totally different than secure 3 or 4 OSPF neighbors, also the method of authentication will effect the utilization percentage, so finally it's depending on your design.
I should take the above points into consideration while I'm using such feature on any series of routers (7600 or not) but Cisco designed 7600 For service providers and high-end enterprise customers, also 7600 is an ideal platform for integrating all aspects of a point of presence (POP), which mean this is the mission of such kind of gears, so I think you are totally free to deploy it as soon as your gear not fully utilized.
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...