Static routes and VLAN/Tunnel as Resource Type

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

 

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.