On Tue, 17 Dec 1996, Chris Caputo wrote:
There is considerable difference between forwarding a packet that happens to contain ICMP data (destination not the router) and responding to a packet that contains ICMP data (destination is the router). In the former, priority in a Cisco is the same for ICMP as it is for UDP or TCP, since this part of the packet is not even being examined. In the later, priority is lower and can be ignored altogether.
I treat ignored (link good, but no response received) ICMP echo requests as an indicator that a router is too loaded. If the router has been pushed to the point of not being able to respond to an ICMP, how well is it going to do when a bunch BGP updates occur? (rhetorical) Both are CPU intensive operations.
Would someone please tell me just why icmp echos are "cpu intensive"? Yes, I know they're in software. So what? A PC can respond to an ethernet loaded with them with a trivial percentage of it's CPU cycles. This sounds to me a whole lot more like a solution to an imagined problem, but I'm prepared to be convinced that responding to pings actually takes a great enough percentage of CPU cycles to slow down packet delivery..... Thanks, David ---------------------------------------------------------------------------- It's *amazing* what one can accomplish when one doesn't know what one can't do!