arp-prefix-limit (Host Fast Reroute)
Syntax
arp-prefix-limit number;
Hierarchy Level
[edit logical-systems logical-system-name routing-instances instance-name routing-options interface interface-name], [edit routing-instances instance-name routing-options interface interface-name]
Description
Override the ARP prefix limit for the specified host fast-reroute (HFRR) profile.
When you configure HFRR, an optional ARP prefix limit sets a maximum for the number of ARP routes and, therefore FRR routes created for each HFRR profile in the routing table. This limit prevents ARP attacks from exhausting the virtual memory on the routing devices.
There are two configuration statements (global-arp-prefix-limit and arp-prefix-limit) that set the ARP prefix limit,
one at the global [edit routing-options host-fast-reroute] hierarchy level and the other at the [edit routing-instances instance-name routing-options interface interface-name] hierarchy level, respectively. The global global-arp-prefix-limit statement sets a default ARP prefix limit for all HFRR profiles
configured on the routing device. The arp-prefix-limit statement
overrides the global-arp-prefix-limit for that HFRR profile
for that protected interface.
Warning system log messages begin when the ARP routes in an HFRR profile reaches 80% of the configured limit. When the number crosses the 100% threshold, the HFRR profile is deactivated. When this happens, all ARP/FRR routes are deleted from the routing table. FRR routes are deleted from forwarding table as well.
After the HFRR profile is deactivated, a blackout timer is started. The timeout value of this timer is the ARP cache timeout (kernel timeout) + the supplementary blackout timer.
There are global and per-HFRR CLI statements (global-supplementary-blackout-timer and supplementary-blackout-timer) to configure the
supplementary blackout timer. The global value is at the [edit
routing-options host-fast-reroute] hierarchy level and applies
to all HFRR profiles on the routing device. The value for the routing-instance
interface is at the [edit routing-instances instance-name routing-options interface interface-name] hierarchy level, and overrides the global value for that HFRR profile
only.
When the blackout timer expires, the HFRR profile is reactivated, and the Junos OS relearns the ARP routes and re-creates the HFRR routes. If the ARP prefix limit is not exceeded again, the HFRR routes will be up.
If an HFRR profile is in the deactivated state, a reevaluation
of the ARP state is preformed during every commit operation or whenever
the routing process (rpd) is restarted with the restart routing command.
Default
If you omit the-arp-prefix-limit statement,
the global-arp-prefix-limit takes effect for all HFRR profiles
on the device. If you omit both of these statements, there is no ARP
prefix limit for host fast reroute.
Options
| number | Maximum number of ARP HFRR routes allowed.
|
Required Privilege Level
routing—To view this statement in the configuration.
routing-control—To add this statement to the configuration.
Release Information
Statement introduced in Junos OS Release 12.2.