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Dazzla_20011's avatar
Icon for Nimbostratus rankNimbostratus
Nov 10, 2010

Source NAT specify real or floating in config?




I have two LTM's in active - standby configuration. We use source NAT so we can load balance services on a different network to which the LTM's are connected. The problem I've found is when using source NAT the LTM uses the floating ip rather than the real address of the active LTM which would cause a routing problem if the standby LTM became Active.



My question is if I remove the floating ip (not needed) will the active LTM use the real address of itself for source NAT? Also is it possible to change the configuration on the LTM to specify if SNAT uses the floating or real address?






2 Replies

  • nathe's avatar
    Icon for Cirrocumulus rankCirrocumulus
    Hi Darren,



    I'm a bit confused on this one. Isn't the purpose of an active/standby config to have a floating ip address? If the standby appliance becomes active the floating ip address should move across as well (arp etc. working fine). If you do remove the floating ip it will use the real self ip of the LTM, however, if a failure occurs (active appliance shuts down for some reason) existing traffic will be dropped as the self ip won't be available.



    Let us know if I've misunderstood your scenario.





  • The only way I could see LTM using a static (non-shared) self IP for sourcing traffic is:



    1. You've manually configured LTM to use a SNAT pool with the static self IP. Obviously, you shouldn't do this as it would cause conflicts when the peer unit is active.



    2. You're looking at the monitor traffic coming from the static self IP instead of the load balanced traffic coming from the floating self IP.



    As Nathan said, you shouldn't have any issues if you use SNAT automap or manually configure anything other than a static self IP for the SNAT pool.