Foundry Networks Switch and Router Installation And Configuration Manual page 441

Disabling Rate Limiting Exemption for Control Packets
By default, the Foundry device does not apply Adaptive Rate Limiting policies to certain types of control packets,
but instead always forwards these packets, regardless of the rate limiting policies in effect.
NOTE: This section applies only to Adaptive Rate Limiting. Fixed Rate Limiting drops all packets that exceed
the limit, regardless of packet type.
Table 14.3 lists the types of control packets that are exempt from rate limiting by default.
Traffic Type
IP multicast IP nodes multicast
IP routers multicast
IP DVMRP router multicast
IP OSPF router multicast
IP OSPF designated router multicast
IP RIP V.2 router multicast
IP VRRP multicast
IP unicast BGP control packet
OSPF control packet
RIP packet
To provide exemption, the CPU examines each packet to determine whether the packet is one of the exempt
control types. If your network does not use these control types and you want to reduce CPU utilization, you can
disable exemption for the control packets on an interface. To do so, use the following CLI method.
NOTE: If your network uses BGP, OSPF, or RIP and you disable exemption, the rate limiting polices can result in
routing protocol traffic being dropped.
To disable rate limiting exemption for control packets on an interface, enter the following command at the CLI
configuration level for that interface:
NetIron(config-if-e1000-25)# rate-limit control-packet no
This command disables exemption of all the control packets listed in Table 14.3 on port 25.
Syntax: [no] rate-limit control-packet no | yes
To re-enable exemption for the interface, enter the following command:
NetIron(config-if-e1000-25)# rate-limit control-packet yes
December 2000
Table 14.3: IP Control Traffic Exempt from Rate Limiting
IP Address IP Protocol or Application
Port
224.0.0.1
224.0.0.2
224.0.0.4
224.0.0.5
224.0.0.6
224.0.0.9
224.0.0.18
TCP port 179 (0xB3)
IP protocol type 89 (0x59)
UDP port 520 (0x0208)
IronClad Rate Limiting
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