Brocade FastIron Ethernet Switch Traffic Management Guide - Manual (Page 77)

CPU rate-limiting
Unnecessary traffic to the switch CPU lowers the efficiency of the CPU and delays handling of other
traffic that requires processing. CPU rate limiting is a CPU protection scheme which limits certain traffic
types.
CPU rate limiting identifies the traffic type and assigns a maximum rate limit to the traffic type. The
traffic types which are subjected to rate limiting include broadcast ARP and other exceptions, such as
TTL exceed, IP MTU failed, reverse path check failed, IP fragments, and unsupported tunneling. Each
of these types is rate-limited individually.
The following table shows the rate limits for each rate-limited packet type and shows which platforms on
which each rate limit applies. These rates cannot be configured by users currently.
CPU rate limits for packet type and applicable platforms TABLE 34
Packet type Rate limit in packets per
second Applicable platforms
ARP 6000 All
IP TTL exceed, or
Reverse path check failed
150 All
IP MTU exceed,
IP tunnel-terminated packets which are fragmented or has
options, or
IP tunnel-terminated packets with unsupported GRE tunnel
header
3000 All
IP Unicast packets mirrored to CPU due to ICMP redirect 100 All
Bridge packets forward to CPU 5000 FCX and ICX
All currently supported FastIron devices support the CPU rate-limiting feature. However, on the FSX
devices, only the following modules support this feature:
• SX-FI-24GPP
• SX-FI-24HF
• SX-FI-2XG
• SX-FI-8XG
• SX-FI48GPP
CPU rate-limiting
FastIron Ethernet Switch Traffic Management Guide 75
53-1003093-03