When executing 'show arp' , it takes an unusually long time to return the output results.

When configuring DNS configuration, the device will go to resolve IPs. The output of 'show arp' takes a long time because the device could not reach DNS or the DNS response is delayed.  

There are two solutions which can solve this issue.

1. Deactivating DNS configuration.

   Or

2. Using no-resolve commands to check the ARP table.

no-resolve—(Optional) Do not attempt to determine the hostname that corresponds to the IP address. See technical documentation on show arp .

Example:

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[master:0][edit]
root@jtac-ex3400-48t-r2037# run show arp no-resolve 
Jan 04 07:01:31
MAC Address       Address         Interface         Flags
00:00:5e:00:01:0b 10.219.19.1     vme.0                    none
02:00:00:00:00:0b 128.0.0.5       bme0.0                   permanent
02:00:00:00:00:0b 128.0.0.6       bme0.0                   permanent
02:00:00:00:00:0b 128.0.0.17      bme0.0                   permanent
Total entries: 4
--------------------

• show arp