Advanced Configuration and Management Guide
Disabling Rate Limiting Exemption for Control Packets
By default, the 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 4.2 lists the types of control packets that are exempt from rate limiting by default.
Table 4.2: IP Control Traffic Exempt from Rate Limiting
Traffic Type |
| IP Address | IP Protocol or Application |
|
|
| Port |
|
|
|
|
IP multicast | IP nodes multicast | 224.0.0.1 |
|
|
|
|
|
| IP routers multicast | 224.0.0.2 |
|
|
|
|
|
| IP DVMRP router multicast | 224.0.0.4 |
|
|
|
|
|
| IP OSPF router multicast | 224.0.0.5 |
|
|
|
|
|
| IP OSPF designated router multicast | 224.0.0.6 |
|
|
|
|
|
| IP RIP V.2 router multicast | 224.0.0.9 |
|
|
|
|
|
| IP VRRP multicast | 224.0.0.18 |
|
|
|
|
|
IP unicast | BGP control packet |
| TCP port 179 (0xB3) |
|
|
|
|
| OSPF control packet |
| IP protocol type 89 (0x59) |
|
|
|
|
| RIP packet |
| UDP port 520 (0x0208) |
|
|
|
|
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:
This command disables exemption of all the control packets listed in Table 4.2 on port 1/1.
Syntax: [no]
To
4 - 20