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suresh09_292033's avatar
suresh09_292033
Icon for Nimbostratus rankNimbostratus
Jan 23, 2018
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Fall back IP

What i understanding regarding fall back IP is that if all virtual servers in pool associated with wide ip are down then DNS will resolve to fall back ip but in my scenario it's happening differently. I have included primary DC and DR virtual server/ip's in pool and fall back ip as Primary DC virtual server IP but when both virtual server are down then in nslookup it's showing both primary and DR VIP ip's instead of only primary DC IP in fall back IP.

 

application delivery
BIG-IP DNS
devops
  • Jason_Brown_314's avatar
    Jason_Brown_314
    Jan 31, 2018

    You need to have the alternate set to fallback for this to use that IP entry.

     

    Also, just to expand - I have just experienced this too and I understand that there is a level of caching done within DNS express in order to try to expedite the reply, you are also using a LDNS (presuming 10.10.10.10 isn't the DNS listener) to resolve this host you could get old answers. I disabled DNS express in my profile and it worked as I expected it should.

     

    being new to the GTM I am also still learning, so this is based on my troubleshooting only.

     

11 Replies

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  • kolom's avatar
    kolom
    Icon for Altostratus rankAltostratus
    Jan 23, 2018

    Hello Suresh, Can you post a snapshot of your pool configuration .

     

  • kolom_265617's avatar
    kolom_265617
    Icon for Cirrostratus rankCirrostratus
    Jan 25, 2018

    Hello suresh,

     

    This behavior is caused by using "Return to DNS" as a fallback method.Return to DNS drops the resolution to BIND. When this mode is used, the typical response will be a list of all virtual servers associated with the Wide IP.

     

    • suresh09_292033's avatar
      suresh09_292033
      Icon for Nimbostratus rankNimbostratus
      Jan 25, 2018

      Thanks Kolom for quick reply, i will try by disabling return to dns option.

       

      Can you please help me to understand the below line from F5 site. "You can also use Return to DNS when you want to limit a pool in a single pool configuration to only one or two load balancing attempts"

       

    • suresh09_292033's avatar
      suresh09_292033
      Icon for Nimbostratus rankNimbostratus
      Jan 31, 2018

       

      I have disable return to dns from fallback method but still its resolving both virtual server ip's in dns. What could be the issue?

       

  • kolom's avatar
    kolom
    Icon for Altostratus rankAltostratus
    Jan 25, 2018

    Hello suresh,

     

    This behavior is caused by using "Return to DNS" as a fallback method.Return to DNS drops the resolution to BIND. When this mode is used, the typical response will be a list of all virtual servers associated with the Wide IP.

     

    • suresh09_292033's avatar
      suresh09_292033
      Icon for Nimbostratus rankNimbostratus
      Jan 25, 2018

      Thanks Kolom for quick reply, i will try by disabling return to dns option.

       

      Can you please help me to understand the below line from F5 site. "You can also use Return to DNS when you want to limit a pool in a single pool configuration to only one or two load balancing attempts"

       

    • suresh09_292033's avatar
      suresh09_292033
      Icon for Nimbostratus rankNimbostratus
      Jan 31, 2018

       

      I have disable return to dns from fallback method but still its resolving both virtual server ip's in dns. What could be the issue?

       

  • Jason_Brown_314's avatar
    Jason_Brown_314
    Icon for Nimbostratus rankNimbostratus
    Jan 31, 2018

    You need to have the alternate set to fallback for this to use that IP entry.

     

    Also, just to expand - I have just experienced this too and I understand that there is a level of caching done within DNS express in order to try to expedite the reply, you are also using a LDNS (presuming 10.10.10.10 isn't the DNS listener) to resolve this host you could get old answers. I disabled DNS express in my profile and it worked as I expected it should.

     

    being new to the GTM I am also still learning, so this is based on my troubleshooting only.