arp (Interfaces)
Syntax
arp ip-address (mac | multicast-mac) mac-address publish;
arp {
aging-timer minutes;
gratuitous-arp-delayseconds;
gratuitous-arp-on-ifup;
interfaces {
interface-name {
aging-timer minutes;
}
}
passive-learning;
purging;
}
Syntax (EX Series)
arp {
aging-timer minutes;
}
Hierarchy Level
[edit interfaces interface-name unit logical-unit-number family inet address address]
[edit logical-systems logical-system-name interfaces interface-name unit logical-unit-number family inet address address]
The edit logical-systems hierarchy is not available
on QFabric systems.
Release Information
Statement introduced before Junos OS Release
7.4.
Statement introduced in Junos OS Release 9.0 for EX Series switches.
Statement introduced in Junos OS Release 11.1 for the QFX Series.
Statement introduced in Junos OS Release 14.1X53-D20 for the
OCX Series.
Description
For Ethernet, Fast Ethernet, and Gigabit Ethernet
interfaces only, configure Address Resolution Protocol (ARP) table
entries mapping IP addresses to MAC addresses. You can enable backup
VRRP routers to learn ARP requests for VRRP-IP to VRRP-MAC address
translation. You can also set the time interval between ARP updates.
NoteBy default, an ARP policer is installed that is shared
among all the Ethernet interfaces on which you have configured the family inet statement. By including the arp statement
at the [edit interfaces interface-name unit logical-unit-number family inet policer] hierarchy
level, you can apply a specific ARP-packet policer to an interface.
This feature is not available on EX Series switches.
When you need to conserve IP addresses, you can configure an
Ethernet interface to be unnumbered by including the unnumbered-address statement at the [edit interfaces interface-name unit logical-unit-number family inet] hierarchy level.
NoteFor EX-Series switches, set only the time interval between
ARP updates.
Options
ip-address—IP address
to map to the MAC address. The IP address specified must be part of
the subnet defined in the enclosing address statement.
mac mac-address—MAC address to map to the IP address. Specify the
MAC address as six hexadecimal bytes in one of the following formats: nnnn.nnnn.nnnn or nn:nn:nn:nn:nn:nn. For example, 0000.5e00.5355 or 00:00:5e:00:53:55.
multicast-mac mac-address—Multicast MAC address to map to the IP
address. Specify the multicast MAC address as six hexadecimal bytes
in one of the following formats: nnnn.nnnn.nnnn or nn:nn:nn:nn:nn:nn. For example, 0000.5e00.5355 or 00:00:5e:00:53:55.
publish—(Optional)
Have the router or switch reply to ARP requests for the specified
IP address. If you omit this option, the router or switch uses the
entry to reach the destination but does not reply to ARP requests.
NoteFor unicast MAC addresses only, if you include the publish option, the router or switch replies to proxy ARP requests.
aging-timer—Time interval
in minutes between ARP updates. In environments where the number of
ARP entries to update is high (for example, on routers only, metro
Ethernet environments), increasing the time between updates can improve
system performance.
gratuitous-arp-delay— Configure a delay for gratuitous ARP requests at the system level.
By default, Junos OS sends gratuitous ARP requests immediately after
network-related configuration changes are made on an interface (for
example, a VLAN ID, MAC address, IP address change, or Aggregated Ethernet deployment). This might lead to the Packet Forwarding Engine dropping some
initial request packets if the configuration updates have not been
fully processed. To avoid such request packets being dropped, you
can configure a delay in gratuitous ARP requests.
gratuitous-arp-on-ifup— Add this statement to the [edit system
arp] hierarchy to configure Junos OS to automatically issue
a gratuitous ARP announcement when an interface is online.
interfaces— Specify
the ARP aging timer in minutes for a logical interface of family type inet.
Values: aging-timer minutes—Time
between ARP updates, in minutes.
Range: 1 through 6,00,000
passive-learning— Configure backup VRRP routers
or switches to learn the ARP mappings (IP-to-MAC address) for hosts
sending the requests. By default, the backup VRRP router drops these
requests; therefore, if the master router fails, the backup router
must learn all entries present in the ARP cache of the master router.
Configuring passive learning reduces transition delay when the backup
router is activated. Learning of ARP mappings (IP-to-MAC address)
by backup VRRP routers or switches for hosts sending the requests
is disabled unless this statement is configured.
purging— Purge obsolete ARP entries
from the cache when an interface or link goes offline.
Required Privilege Level
interface—To view this statement in the
configuration.
interface-control—To add this statement to the configuration.
system—To view this statement in the configuration.
system-control—To add this statement to the
configuration.
