Technical Tip: GLB DNS record not propagated immediately when there is status change in GLB Virtual Server Pool
| Description | This article describes how to enforce immediate DNS answer update when there is status change in GLB Virtual Server Pool. |
| Scope | FortiADC. |
| Solution | When FortiADC GLB host tied to Virtual Server Pool, most configuration enable ‘Backup’ in the Secondary site Virtual Server Pool. In the case of Primary site Virtual Server Pool marked down, FortiADC GLB should update DNS answer with Secondary site Virtual Server Pool IP address.
By default, FortiADC DNS zone Time-to-Live(TTL) is 86400 seconds – 24 hours. When there is a status change in GLB Virtual Server Pool(especially in Active-Backup configuration), external DNS server might cache DNS record and DNS update is not propagated immediately which would cause incorrect DNS resolution or worse a downtime.
Set DNS Zone Time-to-Live(TTL) to an acceptable or desired value. For example, 10 seconds or 300 seconds for faster DNS update.
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