7.6.1.0 - Force10 Networks

Dynamic Counters
By default, counting for the following four applications are enabled:
• IPFLOW
• IPACL
• L2ACL
• L2FIB
For remaining applications, FTOS automatically turns on counting when the application is enabled, and is
turned off when the application is disabled. Please note that if more than four counter-dependent
applications are enabled on a port pipe, there is an impact on line rate performance.
The following counter-dependent applications are supported by FTOS:
• Egress VLAN
• Ingress VLAN
• Next Hop 2
• Next Hop 1
• Egress ACLs
• ILM
• IP FLOW
• IP ACL
• IP FIB
• L2 ACL
• L2 FIB
Link Dampening
Interface state changes occur when interfaces are administratively brought up or down or if an interface
state changes. Every time an interface changes state or flaps, routing protocols are notified of the status of
the routes that are affected by the change in state, and these protocols go through momentous task of
re-converging. Flapping therefore puts the status of entire network at risk of transient loops and black
holes.
Link dampening minimize the risk created by flapping by imposing a penalty for each interface flap and
decaying the penalty exponentially. Once the penalty exceeds certain threshold, the interface is put in an
"error-disabled" state, and for all practical purposes of routing, the interface is deemed to be "down." Once
the interface becomes stable and the penalty decays below a certain threshold, the interface comes up again
and the routing protocols re-converge.
Link dampening:
• reduces processing on the CPUs by reducing excessive interface flapping.
204 Interfaces