Static routes and VLAN/Tunnel as Resource Type

Hi Piotr,

 

If you're asking what the BIG-IP does when you set a static route to point to a VLAN or tunnel instead of (for example) a next-hop gateway, then the BIG-IP should ARP for the destination address regardless of the configured IP addresses on the interface itself. The BIG-IP will ARP for the destination address using a locally configured source self-ip on that VLAN/tunnel.

 

That means that you need a proxy ARP device upstream to see the ARP request and respond.

 

In earlier software versions and under certain conditions, the BIG-IP would broadcast packets (L2 ff:ff:ff:ff:ff:ff) to the IP destination when the ARP goes unanswered. Some routers would happily route that, but the behaviour was deemed to be undesirable and should no longer occur.

 

Regards, Michael.

 

Hi,

 

Thanks a lot for answer. I hope I can understand it now but to be sure..

 

Scenario (Route definition):

 

• Destination: 192.168.1.0/24
• Resource: Use VLAN/Tunnel
• VLAN/Tunnel: VLAN_X

Now there is a question how VLAN has to be defined:

 

• Just VLAN assigned to given Interface
• As above plus Self IP assigned to VLAN

Assuming that second option above is true, VLAN_X def is:

 

• Self IP: 192.168.2.1/24

Having above def what will happen when packet with destination IP 192.168.1.1 is processed?

 

• BIG-IP broadcast ARP request for 192.168.1.1
• If there is any proxy ARP device that knows route to 192.168.1.1 it will answer with own MAC
• BIG-IP will send packet with dst IP 192.168.1.1 and dst MAC of proxy ARP device
• Proxy ARP device will send this packet using defined route either to destination host or to another upstream device

Is above correct?

 

I wonder what do you mean by "the BIG-IP would broadcast packets (L2 ff:ff:ff:ff:ff:ff) to the IP destination when the ARP goes unanswered" - packet will be send with dst IP 192.168.1.1 and broadcast MAC?

 

Piotr