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mreco_159588's avatar
mreco_159588
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Jun 08, 2017

No response after added virtual server IP address as floating self-IP address

Hi,   I have an F5 HA pair that serves several virtual servers.   VS1: ip1   VS2: ip2   Now, the IP address of VS1 (ip1) was already defined as a floating self-IP, but I found out that th...
application delivery
BIG-IP
LTM
self ip
virtual server
  • mreco_159588's avatar
    mreco_159588
    Jun 14, 2017

    It was driving me nuts, since I just want to understand what's going.

     

    After reading this post: https://devcentral.f5.com/questions/self-ip-address-selection-with-multiple-to-choose-from, I checked the firewall logs again. And now the pieces fit.

     

    On the Virtual Servers I have SNAT Automap enabled. When I only have one floating self IP, that floating self IP is used to initiate traffic to backend servers. When I add more floating self IPs, it will use any of those floating self IPs to initiate traffic towards the backend servers.

     

    The firewall between the F5 and the backend servers does not accept this traffic, meaning not actually the VS stopped responding after I added the VS IP address as a floating self IP, but the firewall blocked traffic towards the backend servers.

     

    So, conclusion (just to summarize):

     

    • only one floating self IP is needed for SNAT communication towards the backend servers (if the amount of connections is less than 65000, otherwise more are needed and I must define a SNAT pool or allow the other floating IP addresses to communicate to the backend servers)
    • I will remove the unneeded floating self IP, since they're not needed for a VS to function as a listener IP

    Thanks all for your help!

     

marin_266716's avatar
marin_266716
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Im confused, you said floating IP but you also said VS, are you adding a floating IP and thinking it will be the VIP for a pool?

 

VS1 = VIP1 (Application 1) VS2 = VIP2 (Application 2)

 

Self IP = IP in segment used to to reach into segments for monitoring or other purposes.

 

A Self IP is just that, in an HA cluster you could have 2-3 IP's per VLAN. 2x would be 1 Self IP (Non-Floating) per device in your HA group. The 3rd IP would be the floating IP added to the Active node and synced across to the standby. Floating IP's sync, self IP's do not. The Floating IP can be used as a default gateway for instance since it will always follow the active member.

 

What are you trying to accomplish with said "Self/Floating IP"

 

marin_266716's avatar
marin_266716
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Jun 09, 2017

I would assume there is then an IP conflict when you assign the IP of the VS to the floating IP on the self side. This would then cause there to be 2x MAC addresses for the same IP on the switch side thus the IP conflict. Are the working VS's and this VS in question here all in the same subnet? Are they even on the same F5?

 

From the working side. Can you give an example IP of a VS and the 2x Self-IP's and the Floating (which should match the VS IP)? Also if you can tell me which VLAN's are trunked in your "Reals" and "Virtuals" along with the VLAN that said "working" VS is on?

 

On the VS that works, but also has a Floating of the same IP, I have a sneaking suspicion that the VLAN that supports that network is not trunked on the side where the "Floating" IP is used. This would mean it is on the device on say the "Reals" interface but the VLAN is not there. If the IP is present but no VLAN on that trunk, there wouldnt be a conflict.