floating IP and self IP

Hey ni, there's a host of reasons for this;

 

1) Only the primary device holds the floating IP, how would you monitor the standby device?

 

2) The standby would not be able to take part in dynamic routing (if enabled)

 

3) The standby would not be able to build an ARP table until it became active, which would cause a bit of delay

 

4) ConfigSync wouldn't work over that VLAN

 

5) Network failover wouldn't work over that VLAN

 

6)Health monitors couldn't be run by the standby until it became active

 

7)Active/active would not be possible

 

And so on...

 

If you want an answer from a network perspective...

 

non-floating IP is a physical IP address on a local device interface

 

floating IP is a logical IP address on the same network pointing to the active device's interface in HA setup. It's not needed if you have only a standalone unit.

 

 

An analogy would be setting up an VRRP or HSRP where you need to assign an IP address to a physical interface before setting up the virtual IP address.

 

 

Hi Beneath:

 

Thanks for your reply. Can you tell me why is Active/active would not be possible?

 

 

Hi Amnard:

 

Thanks for your reply. can you tell me what the difference between physical IP and logical Ip?

 

Hi All:

 

whether Each VLAN has the VRRP protocol broadcast or not?

 

Active/active would not be possible as the external VLAN could be active on one device and the internal on another, if the device that's active for the external VLAN had no internal IP address (as the other device would have the floating Self IP) it could not send traffic on the internal VLAN.

 

 

F5 BIG-IP/TMOS does not use VRRP.

Hi beneath:

 

"Only the primary device holds the floating IP, how would you monitor the standby device?"

 

whether the primary device each VLAN can monitor the standby device non-floating IP or not ?

 

How primary device monitor the standy device except failover IP adress?

 

 

Thanks a lot !

 

best regards!

 

I meant more in relation to external monitoring systems, network failover (which you'd ideally use on every VLAN) and the like.

A physical IP address is unique to an interface on a hardware device on your network.

 

When you have multiple hardware devices in the same HA group, the logical IP address typically points to the active hardware device's physical IP address. When you have an HA failover, it will point to the new active device.

 

Under F5, floating interface carries an additional meaning. It's used for communicating with the back-end servers. Therefore, it is NOT needed on the subnet that the VS are on unless you have back-end servers on the same subnet.

 

 

I'd highly recommend a floating address for any VLAN that is used for Virtual Servers unless clients are on the same VLAN. You wouldn't want to route traffic to the active device non-floating Self IP, if a failover occurred you've lost your service!