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Step 3: Configure a Static Address Resolution Protocol Table Entry

Purpose

Configure a static Address Resolution Protocol (ARP) entry to allow a packet to be sent out of a looped Ethernet interface.

NOTE: Remove the static ARP entry at the end of the loop test after you have completed the ping test, checked interface statistics, and monitored interface traffic.

Action

To configure a static ARP table entry for a Gigabit Ethernet interface, follow these steps. You can follow the same procedure to configure a static ARP entry for a Fast Ethernet interface.

  1. Find the Media Access Control (MAC) address for the Gigabit Ethernet interface:
    2. user@host> show interfaces ge-fpc/pic/port
  2. In configuration mode, go to the following hierarchy level:
    3. [edit]

    user@host# edit interfaces interface-name unit logical-unit-number family inet 
address address
  3. Configure the static ARP entry:
    4. user@host# set arp ip-address mac mac-address

    

    

    

       
NOTE: The MAC address used should be the same as the physical address of the port being tested because this allows the port to receive the frames when you run the ping test.
  4. Verify the configuration:
    5. user@host# show
  5. Commit the configuration:
    6. user@host# commit
  6. Verify that the static ARP entry is installed:
    7. user@host# run show arp no-resolve

Sample Output

user@host> show interfaces ge-7/2/1

Physical interface: ge-7/2/1, Enabled, Physical link is Down

  Interface index: 44, SNMP ifIndex: 35

  Link-level type: Ethernet, MTU: 1514, Source filtering: Disabled

  Speed: 100mbps, Loopback: Disabled, Flow control: Enabled

  Device flags   : Present Running Down

  Interface flags: Hardware-Down SNMP-Traps

  Link flags     : None

  Current address: 00:90:69:8d:2c:db, Hardware address: 00:90:69:8d:2c:db

  Input rate     : 0 bps (0 pps), Output rate: 0 bps (0 pps)



[edit interfaces ge-7/2/1 unit 0 family inet address 10.108.120.1/30]

user@host# set arp 10.108.120.2 mac 00:90:69:8d:2c:db



[edit interfaces ge-7/2/1 unit 0 family inet address 10.108.120.1/30]

user@host# show 

arp 10.108.120.2 mac 00:90:69:8d:2c:db;



[edit interfaces ge-7/2/1 unit 0 family inet address 10.108.120.1/30]

user@host# commit 

commit complete



[edit interfaces ge-7/2/1 unit 0 family inet address 10.108.120.1/30]

user@host# run show arp no-resolve 

MAC Address       Address         Interface     Flags

00:90:69:8d:2c:db 10.108.120.2    ge-7/2/1.0    permanent

00:e0:34:bb:8c:40 209.211.135.1   fxp0.0        none

00:a0:a5:28:0c:70 209.211.135.8   fxp0.0        none

00:a0:a5:12:12:c7 209.211.135.10  fxp0.0        none

00:90:ab:3c:68:a0 209.211.135.31  fxp0.0        none

08:00:20:a1:53:15 209.211.135.65  fxp0.0        none

00:a0:cc:66:3e:85 209.211.135.98  fxp0.0        none

Total entries: 7

What It Means

The sample output is for Steps 1 through 6 and shows that a static ARP entry was configured on Gigabit Ethernet interface ge-7/2/1. The MAC address used is the same as the physical address of the port being tested because this allows the port to receive the frames when you run the ping test. The port is working as expected if you see that the time to live (TTL) expired; if you do not receive a response to your ping test, it indicates a hardware problem.

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