It is similar to SVI’s in cisco language  in which we assign the IP Address to the VLAN. Self IP address is an IP address in F5 which is assigned to a VLAN. For every self IP address that we create for a VLAN, the BIG-IP System will automatically allocate a MAC Address. Self IP addresses serve below purpose:-

1)      At the time of sending the message to the destination server, the BIG-IP system will consider the Self IP address of its vlan to find out the appropriate VLAN in which the destination server belongs. Lets say we have an Internal Vlan and the Self ip address of this vlan is 10.0.0.200 with a subnet mask of /24 (255.255.255.0) & the destination server’s IP is 10.0.0.210 with a netmask of /32(255.255.255.255), the BIG-IP system looks that the Server’s IP address belongs to the same range of Internal Vlan’s Self IP address, that is why it will send the message to that vlan. In other words, BIG-IP System will send a message to the interface that we have assigned to that Vlan.

2)      Self IP address can be used as a default gateway for servers which are on the internal VLAN.

3)      Self IP address is also used to send monitor probes to multiple or a group of servers which belong to a particular vlan.

We normally need a static Self IP address and a floating Self IP address for the default Vlans – Internal and External. Post the configuration for Self IP’s for internal and external Vlan, we can create these Self IP addresses for other vlans also. We can also configure Self-IP addresses when we run setup utility on BIG-IP F5 which will reside in partition Common.

Types of Self IP addresses:-