DNS randomly returns switch ip as client ip ??

  • Hey,

    have the following strange behaviour after update from 2.3.3 to 2.4.2-p1 . PFsense DHCP Server is serving IP with DNS Resolver enabled.

    Linux environment (Clients and Server).
    Sometimes when i try to ping a client name from a random server, pfsense DNS Resolver returns the IP of my core switche instead of client IP.  For me this seems to appear randomly. DHCP Lease in PFsense shows right ip. After rebooting client, DNS for this client works again.

    Had no issue before update to 2.4.2-p1 .. Does someone have an idea whats wrong here ?


  • i guess dns resolver has some internal cache … is there maybe a TTL for cache entries ? Can this be a reason ?

  • LAYER 8 Global Moderator

    DNS without a TTL would be nuts ;)

    Yes the default ttl for a host override or static reservation would be 3600 seconds or 1 hour.  I do not have normal dhcp clients register but would assume they would be the same.. If a client looks up some it would get that ttl..  It would not ask dns again for that fqdn until the ttl expires in the local clients cache.

    Unless you flush the clients local cache..

    windows can do this with

    ipconfig /flushdns

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