DNAT rule not working - 5 static address block from ISP

I have an ERX running 1.9.

5 static block from the cable ISP  a.b.c.24/29

Gateway = a.b.c.25

Usable = a.b.c.26-30

I have a.b.c.27 and a.b.c.29 assigned to eth0 Internet interface.  

WAN_IN rule to allow destination udp 69.

DNAT rule translation 192.168.10.11 udp 69 destination a.b.c.27 port 69

Problem - I need internet clients (ip phones at some cust sites) to connect tftp (udp 69) to a.b.c.27 and download a logo file.from internal tftp server 192.168.10.11.  Neither my dnat count nor my rule stat shows any increment.

Any ideas what I need to change?.