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Maneesh_72711's avatar
Maneesh_72711
Icon for Cirrostratus rankCirrostratus
Aug 16, 2017

DNS server loadbalancing

Have a query I am loadbalacing 3 DNS Servers on LTM behind a VIP. The issue is when my windows server queries a public domain it appends my local domain suffixes to it which my public DNS Server does not understand and provides NXdomain and wasting time for those DNS resolutions finally resolving to correct domain name. Is there a way possible I can restrict this behavior on LTM so that it stops adding local suffixes so that it immidiately responds to correct yahoo.com DNS query than going around trying to look for local suffixes added domain.

 

tcpdump -nni 0.0 host x.x.x.x tcpdump: verbose output suppressed, use -v or -vv for full protocol decode listening on 0.0, link-type EN10MB (Ethernet), capture size 65535 bytes 08:10:22.647140 IP z.z.z.z.65397 > q.q.q.q.53: 245+ A? yahoo.com.int.introot.biz-intl.com. (54) in slot1/tmm0 lis= 08:10:24.650629 IP z.z.z.z.65398 > q.q.q.q.53: 246+ AAAA? yahoo.com.int.introot.biz-int.com. (54) in slot1/tmm3 lis= 08:10:26.650813 IP z.z.z.z.65400 > q.q.q.q.53: 247+ A? yahoo.com. (27) in slot1/tmm0 lis= 08:10:26.655571 IP q.q.q.q.53 > z.z.z.z.65400: 247 3/0/0 A 206.190.36.45, A 98.139.180.149, A 98.138.253.109 (75) out slot1/tmm0 lis=/Common/proxy-dns.bigip.it.biz-int.com-v-53 08:10:26.810124 IP z.z.z.z.65401 > q.q.q.q.53: 248+ AAAA? yahoo.com. (27) in slot1/tmm1 lis= 08:10:26.816825 IP q.q.q.q.53 > z.z.z.z.65401: 248 3/0/0 AAAA 2001:4998:c:a06::2:4008, AAAA 2001:4998:44:204::a7, AAAA 2001:4998:58:c02::a9 (111) out slot1/tmm1 lis=/Common/proxy-dns.bigip.it.biz-int.com-v-53

 

application delivery
LTM

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  • Maneesh_72711's avatar
    Maneesh_72711
    Icon for Cirrostratus rankCirrostratus
    Aug 17, 2017

    Anyone got a clue if this is achievable via irule or some other means? Probably stripping the added suffix domain and resolving the initial domain ?

     

  • Nazir_52641's avatar
    Nazir_52641
    Icon for Cirrus rankCirrus
    Aug 17, 2017
    Hi Maneesh,
    This is an issue with windows server, to avoid adding local domain by windows add . at the end of fqdn.

    Example instead of using command 
    nslookup yahoo.com
    use command
    nslookup yahoo.com.

    Thanks

    Syed Nazir

    • Maneesh_72711's avatar
      Maneesh_72711
      Icon for Cirrostratus rankCirrostratus
      Aug 18, 2017

      Yep aware of it Nazir is an issue with Windows. Issue is how can I force users to add . in the end. Can we do something via i-rules so that it strips the trailing suffixes ?