bootp through the ltm

I can get the initial bootp request through the LTM, but the response doesn't make it back through because of what a dhcp response looks like. Here is what I see in my testing.

 

 

DHCP Server: 10.10.10.100

 

External: 10.10.10.10

 

Internal: 192.168.10.10

 

Client: none (about to get dhcp to 192.168.10.100)

 

 

Client sends out bootp request destination 255.255.255.255 and source 0.0.0.0

 

LTM catches it in the vip and shoots it out the other end.

 

Here we can either SNAT it or not SNAT it. Either way, the source mac address is now the BIG-IP.

 

When the DHCP server gets it, it responds with a packet, source IP 10.10.10.100 dest ip: (192.168.10.100). Destination mac, LTM’s mac address.

 

Now that packet reaches the LTM

 

If you have a forwarding virtual on the external side, TMM accepts it and then says, ok, where is this destination IP 192.168.10.100? I have no arp entry so I’ll ask. It then sends and arp query out the client side asking for 192.168.10.100. No one owns it and the packet dies.

 

 

Something in the LTM needs to receive the DHCP request and act as a dhcp proxy where it remembers the original bootp request and can recognize that the bootp response belongs to that client’s mac.

 

That’s what a linux program called dhcprelay is designed to do, but we haven’t implemented that on LTM.

 

 

I think we need to request that F5 add this to their product by creating a support case.