ip prefix-limit

Function

The ip prefix-limit command configures a limit on the number of IPv4 public route prefixes.

The undo ip prefix-limit command restores the default configuration.

By default, the maximum number of IPv4 public route prefixes is not limited.

Format

ip prefix-limit number { alert-percent [ route-unchanged ] | simply-alert }

undo ip prefix-limit

Parameters

Parameter	Description	Value
number	Specifies the maximum number of IPv4 public route prefixes.	The value is an integer ranging from 1 to 4294967295.
alert-percent	Specifies the percentage of the maximum number of IPv4 public route prefixes. If you specify alert-percent in the command, when the number of IPv4 public route prefixes exceeds number x alert-percent/100, an alarm is generated. Additional IPv4 public route prefixes can still be added to the routing table until the number of IPv4 public route prefixes reaches number. Subsequent route prefixes are discarded.	The value is an integer ranging from 1 to 100.
route-unchanged	Indicates that the routing table remains unchanged. If you decrease alert-percent after the number of IPv4 public route prefixes exceeds number, whether the routing table remains unchanged is determined by route-unchanged: If you specify route-unchanged in the command, the routing table remains unchanged. If you do not specify route-unchanged in the command, the system deletes the routes from the routing table and re-adds routes. By default, the system deletes the routes from the routing table and re-adds routes.	-
simply-alert	Indicates the following function: If you specify simply-alert in the command, new IPv4 public route prefixes can still be added to the routing table and only an alarm is generated after the number of IPv4 public route prefixes exceeds number.	-

Views

System view

Default Level

2: Configuration level

Task Name and Operations

Task Name	Operations
route-base	write

Usage Guidelines

Usage Scenario

If thedevice imports a large number of routes, system performance may be affected when processing services because the routes consume excessive system resources. To improve system security and reliability, run the ip prefix-limit command to configure a limit on the number of IPv4 public route prefixes. When the number of IPv4 public route prefixes exceeds the limit, an alarm is generated, prompting you to check whether unneeded IPv4 public route prefixes exist.

Configuration Impact

After the ip prefix-limit command is run, thedevice may discard unneeded IPv4 public route prefixes.

If the number of IPv4 public route prefixes exceeds the value calculated from number* alert-percent/100, an alarm (L3VPN_1.3.6.1.2.1.10.166.11.0.3 L3VPN_MIB_TRAP_MID_THRESH_EXCEED) is generated.
If the number of IPv4 public route prefixes exceeds number, an alarm (L3VPN_1.3.6.1.2.1.10.166.11.0.4 L3VPN_MIB_TRAP_THRESH_EXCEED) is generated.
If the number of IPv4 public route prefixes falls below the value calculated from number* alert-percent/100, a clear alarm (L3VPN_1.3.6.1.4.1.2011.5.25.177.1.3.8 L3VPN_MIB_TRAP_THRESH_CLEARED) is generated.
If the number of IPv4 public route prefixes exceeds number, a clear alarm (L3VPN_1.3.6.1.2.1.10.166.11.0.6 L3VPN_MIB_TRAP_MID_CLEARED) is generated.

Precautions

If the ip prefix-limit command is run more than once, the last configuration overrides the previous one.

After the number of IPv4 public route prefixes exceeds the limit, note the following rules:

If you run the ip prefix-limit command to increase or the undo ip prefix-limit command to delete the limit, thedevice relearns IPv4 public route prefixes.
Direct and static routes can still be added to the IP routing table.

Example

# Configure simply-alert so that only an alarm is generated when the device imports more than 1000 IPv4 public route prefixes.

<HUAWEI> system-view
[~HUAWEI] ip prefix-limit 1000 simply-alert