Configuration Guide User guide

FastIron Configuration Guide 1787

53-1002494-02

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.

Table 293 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.

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

TABLE 293 CPU rate limits for packet type and applicable platforms

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