[j-nsp] SRX - DHCP client is not working right

[martin papik]

Hi,
a have detected very strange behaviour when SRX interface is configured 
as DHCP client interface and this interface (untrust zone)  is connected 
to cable ISP modem (Motorola SurfBoard SB 5101). The ISP is UPC company 
(Europe).  The IP assigned address from ISP is related to MAC address of 
SRX interface. But assigned IP is not right. With different device (like 
linksys WRT with clone MAC) the assigned IP is OK.
I found same problem in juniper forum discussion here:
http://www.juniperforum.com/index.php?topic=8129.0

My conf is:

version 11.1R3.5;

interfaces {
     fe-0/0/0 {
         unit 0 {
             family inet {
                 dhcp;
             }
         }
     }

......

  security-zone untrust {
             screen untrust-screen;
             interfaces {
                 fe-0/0/0.0 {
                     host-inbound-traffic {
                         system-services {
                             dhcp;
                             ping;
                         }
                     }
                 }
             }
         }

Have anybody some idea why assigned IP from ISP is not  right (MAC is 
registred by ISP and with another devices DHCP client working with good 
IP)? I was thinking about TTL parameter, but I dont know how I can 
change it..............

Thanks
Martin