IT 3100 : Systems Design and Administration I

DNS Troubleshooting

SOA Fields

What is SOA? (Start of Authority)

    @       IN      SOA (

SOA Fields

    2017012001      ; Serial
    3600   ; Refresh
    300   ; Retry

SOA Fields

    241920  ; Expire
    60)   ; Negative Cache TTL

DNS Debugging

Steps (order matters)



Master Troubleshooting

Slave Troubleshooting

Delegation (Recursive Lookups)

We haven’t enabled this fully yet, but


After making changes on registrar to point to your nameservers, may have to wait for cache to expire before changes will appear.

Do digs from top down to troubleshoot.