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Blackmail88's avatar
Blackmail88
Icon for Nimbostratus rankNimbostratus
Aug 12, 2024

About Self IP, and Virtual IP

hi all,

 

i just learning F5 about 1 month, so i have a lot of quiestion regarding how actually F5 works. especially about Self IP and Virtual IP. as far as i know Self IP is an IP address for VLAN and Virtual IP is an IP Address that will be used by the user to connect to real server. but about a couple days a go i notice something that i dont understand. so for better explanation i think im gonna tell you about my lab

 

  1. i have a F5 (virtual) and configuring as one arm topology
  2. the F5 connect to my switch
  3. the real server and user alson connect to same switch
  4. inside switch i configured 3 VLAN ( VLAN 1 for user, VLAN 2 for real server, and VLAN 3 for IP VS)
  5. VLAN 1 = 192.168.0.0/24, VLAN 2 = 192.168.1.0/24 AND VLAN 3 = 192.168.2.0/24
  6. and for self IP im using VLAN 3

so the problem that i found was, im testing create a IP VS but on different segment (172.16.1.1/24) and i assign to existing server. then i tested from the user and its works. 

 

so based on that experience, is that any connection between IP address on Self IP and IP Address on VS ?

 

hopefully i got enlighment from this forum ^^

F5 SelfIP
  • boneyard's avatar
    boneyard
    Aug 12, 2024

    Something like above? You can easy make such drawing with draw.io or such, it helps a lot in explaining networks and asking questions about them.

     

    Then indeed, as long as the user knows that the virtual server IPs can be reached via the self IP through routing there is no actually TCP connection with the selfIP.

  • boneyard's avatar
    boneyard
    Icon for MVP rankMVP
    Aug 12, 2024

    In a case like this a network drawing really helps. Also im missing some details like to routing setup. You say switch but do you mean a layer 3 switch or really a layer 2 switch? In that cause where are the gateways for the real server and user network?

     

    Assuming you are pointing your user(s) towards the self IP with a route then the traffic will end up on the BIG-IP it will handle it. That is on routing level, not on TCP connection level between client and server.

  • Blackmail88's avatar
    Blackmail88
    Icon for Nimbostratus rankNimbostratus
    Aug 12, 2024

    hi boneyard

     

    thanks alot for your response to my thread hehee, anyway YES it is a L3 switch, all segments are use the L3 switch as the gateway. for topology its more like a letter "T" hopefully you can imagine it ^^

     

    also, based on you assumption, i can say there is no relation between Self IP and Virtual IP, as long as the source can reach that ip segment ?

     

    thanks and regards

    bram,

    • boneyard's avatar
      boneyard
      Icon for MVP rankMVP
      Aug 12, 2024

      Something like above? You can easy make such drawing with draw.io or such, it helps a lot in explaining networks and asking questions about them.

       

      Then indeed, as long as the user knows that the virtual server IPs can be reached via the self IP through routing there is no actually TCP connection with the selfIP.

  • Blackmail88's avatar
    Blackmail88
    Icon for Nimbostratus rankNimbostratus
    Aug 12, 2024

    i get it know, thanks alot boneyard for your explanation also the drawings, really appreaciate