Symptom
High number of packets on inband with possible high cpu and a contention to control packets due to DTAG TTL 1 (fabricpath ttl 1) packets.
Typically seen with FP OAM feature or a loop in Fabricpath.
Conditions
Only applicable for 7.x releases and above
Further Problem Description
When we shut SVI on both N7k in VPC+ & HSRP network in 7.x or later code. It result into fabricpath loop. Traffic in that vlan might punt to CPU.
After shutting SVI, vmac in hardware points to flood-to-vlan. This might create loop in fabricpath network.
Rate-limiter are modified to drop those packet reaching CPU.
Few changes added in code 8.1.1 and later.
Added new field for fabric path ttl (fp-ttl) in hardware rate limiter.
Either we can have lisp enabled or fp-ttl. Because of some limitation, we can't have both enabled together. By default lisp will be enabled.
We are assuming, we don't need lisp and fabricpath together for that module.
We need to enable fp-ttl rate limiter to drop those packets.
hardware rate-limiter layer-2 lisp-map-cache disable >>> disable lisp in rate limiter
hardware rate-limiter layer-2 fp-ttl module >>> Enable fabricpath ttl in rate limiter
Ex: hardware rate-limiter layer-2 fp-ttl 10 module 1 >>> allow 10 packets at a time in fp-ttl field in rate limiter.
