DNS caching on EdgeSWG (ProxySG)

Products

• ProxySG Software - SGOS
• ISG Proxy
• SG-VA

Issue/Introduction

You want to know if resolved result is cached in proxy.
You want to know length of time DNS entry is held in cache.

Resolution

Access EdgeSWG via SSH and perform following command via CLI:
 ProxySG#test dns www.example.com
 
If result is not in proxy cache you will see a MISS in the result output:

     ProxySG#test dns www.example.com
     Performing DNS lookup for: www.example.com

     Sending A query for www.example.com to x.x.x.x.

     DNS Response data:
     Official Host Name: www.example.com
     Resolved Addresses:
       x.x.x.x
     Cache TTL: 299, cache MISS
     DNS Resolver Response: Success

If result was delivered from proxy cache you will see a HIT in the result output:

     ProxySG#test dns www.example.com
     Performing DNS lookup for: www.example.com

     DNS Response data:
     Official Host Name: www.example.com
     Resolved Addresses:
       x.x.x.x
     Cache TTL: 282, cache HIT
     DNS Resolver Response: Success

 

If result is delivered with TTL value of 0 (zero), that entry is not cacheable by the proxy.

     ProxySG#test dns www.example.com
     Performing DNS lookup for: www.example.com

     Sending A query for www.example.com to x.x.x.x.

     DNS Response data:
     Official Host Name: www.example.com
     Resolved Addresses:
       x.x.x.x
     Cache TTL: 0, cache MISS
     DNS Resolver Response: Success

Additional Information

The TTL (Time To Live) is expressed in seconds and tells resolving name servers how long DNS information should be cached.