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scott_messler_1's avatar
scott_messler_1
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Jul 24, 2015

BIG-IP LTM - Trouble with SNAT to Webserver (IIS)

Greetings,

 

First off I am pretty new to F5 and my team adopted some BIG-IP units that had already been configured. Basically there are 2 VLANs trunked in though a port channel. Each VLAN has 2 Self IPs, one local and one floating. There were also 2 SNAT pools configured, each with 5 IPs one for each VLAN. There was also a VIP on VLAN 2 pointing to a webserver also on VLAN 2 that is using the SNAT pool from VLAN 2. When I try to configure a new VIP on VLAN 2 pointing to a new webserver on VLAN 2 using the SNAT pool from VLAN 2, the connection fails. However the original VIP is working. Also when I switch the new VIP to use the SNAT pool from VLAN 1 that VIP starts working. Basically I need the new VIP to use the SNAT pool from VLAN 2. I ran some tcpdumps and the IPs from SNAT pool 2 never received a SYN-ACK response. Also from the IIS logs it appears there was never any connection from that SNAT pool. I also changed the pool for the new VIP to point to the same pool as the old VIP and the new VIP fails but the old VIP is still working.

 

I am not really what the next steps are in troubleshooting this issue and any help would be greatly appreciated.

 

Thanks, Scott

 

application delivery
LTM

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  • arpydays's avatar
    arpydays
    Icon for Nimbostratus rankNimbostratus
    Jul 24, 2015

    From the cli do tmsh list ltm virtual xxx for both VSs and check for any differences when they point to the same pool.

     

  • scott_messler_1's avatar
    scott_messler_1
    Icon for Nimbostratus rankNimbostratus
    Jul 24, 2015

    Virtual Servers are configured exactly the same, thanks for the tip though I've been trying to learn more about the tmos shell.

     

    Update: I was able to connect in though SNAT pool 2 temporarily ~maybe for 5 minutes before it started rejecting connections again. I had not made any changes.

     

    Thanks, Scott