Router overwhelmed by flow setup


We recently changed our edge router to the internet from a CISCO to an EXTREME S-Series. Which is flow-based. Now the sheer amount of flows is bogging the router down - which is why we’re trying to reduce the total number of flows.

Currently we’re forwarding DNS requests to instead of doing recursion ourselves and in a next step we’'re turning off our public NTP server (just to test things).


We also have an S-Series, and it melted under the load of public NTP. has more details, but the money quote is “Apparently it has a limit of 512k flows over 120 seconds, which works out to be 4266 flows/second.” See also these KB articles:

In the end I reconfigured my network so traffic to the NTP server never touched the S-Series.