Configuring Rate Limiting on ARP Miss Messages Globally, in a VLAN, or on an Interface
Context
If a network device is flooded with IP packets that contain unresolvable destination IP addresses, the device generates a large number of ARP Miss messages. This is because the device has no ARP entry that matches the next hop of the route. IP packets triggering ARP Miss messages are sent to the device for processing. The device generates a large number of temporary ARP entries and sends many ARP Request packets to the network, consuming considerable CPU and bandwidth resources.
To avoid the preceding problems, it is recommended that you configure rate limiting on ARP Miss messages on the gateway.
Rate-limiting ARP Miss messages globally: limits the number of ARP Miss messages processed on the entire device.
Rate-limiting ARP Miss messages in a VLAN: limits the number of ARP Miss messages processed on all interfaces in a VLAN. The configuration in a VLAN does not affect IP packet forwarding on interfaces in other VLANs.
Rate-limiting ARP Miss messages on an interface: limits the number of ARP Miss messages processed on an interface. The configuration on an interface does not affect IP packet forwarding on other interfaces.
If rate limiting on ARP Miss messages is configured in the system view, VLAN view, and interface view, the device uses the configurations in the interface view, VLAN view, and system view, in that order.
If you want the device to generate alarms to notify the network administrator of a large number of discarded ARP Miss packets, enable the alarm function. When the number of discarded ARP Miss packets exceeds the alarm threshold, the device generates an alarm.
Only the S5720-EI, S5720-HI, S5720I-SI, S5720S-SI, S5720-SI, S5735-L, S5735S-L, S5735S-L-M, S5735-S, S5735S-S, S5735-S-I, S5730-HI, S5730S-EI, S5730-SI, S5731-H, S5731-S, S5731S-H, S5731S-S, S5732-H, S6720-EI, S6720-HI, S6720-LI, S6720S-EI, S6720S-LI, S6720S-SI, S6720-SI, S6730-H, S6730S-H, S6730-S, and S6730S-S support this function.
Procedure
- Run system-view
The system view is displayed.
- (Optional) Run interface interface-type interface-number or vlan vlan-id
The interface view or VLAN view is displayed.
If you configure rate limiting on ARP Miss messages in the system view, skip the preceding step.
- (Optional) On an Ethernet interface, run undo portswitch
The interface is switched to Layer 3 mode.
By default, an Ethernet interface works in Layer 2 mode.
Only the S5720-EI, S5720-HI, S5730-HI, S5731-H, S5731-S, S5731S-H, S5731S-S, S5732-H, S6720-EI, S6720-HI, S6720S-EI, S6730-H, S6730S-H, S6730-S, and S6730S-S support switching between Layer 2 and Layer 3 modes.
- Run arp-miss anti-attack rate-limit enable
Rate limiting on ARP Miss messages is enabled.
By default, rate limiting on ARP Miss messages is disabled.
- Run arp-miss anti-attack rate-limit packet packet-number [ interval interval-value ]
The maximum rate and rate limiting duration of ARP Miss messages are set.
By default, the device can process a maximum of 100 ARP Miss messages per second.
- (Optional) Run arp-miss anti-attack rate-limit alarm enable
The alarm function for ARP Miss packets discarded when the rate of ARP Miss packets exceeds the limit is enabled.
By default, the alarm function is disabled.
- (Optional) Run arp-miss anti-attack rate-limit alarm threshold threshold
The alarm threshold for ARP Miss packets discarded when the rate of ARP Miss packets exceeds the limit is set.
By default, the alarm threshold is 100.