Created: 27-Feb-2001
Modified: 27-Feb-2001
By: Lawrence Baldwin
SonicWall (216.78.192.97) wants to do a DHCP Renew.
In preparation to send to the DHCP server (209.215.49.87) is should be sending ARP requests to lookup the default gateway IP address (216.78.192.97). Instead it ARPs directly for the DHCP server IP (209.215.49.87) Frames (14-16).
Since this host is NOT on the local subnet, no one responds. Lastly, in Frame 17 the Sonicwall sends a syslog record to a remote host. The detail of this message state "DHCP Renew Request failed". This is a bit mis-leading since the Renew request was never actually sent, it's really the ARP lookup that is failing.
Frame Status Source Address Dest. Address Size Rel. Time Delta Time Abs. Time Summary
14 Sonic 0FC0F5 Broadcast 60 0:01:04.842 0.049.285 02/27/2001 03:46:18 PM ARP: C PA=[209.215.49.87] PRO=IP
15 Sonic 0FC0F5 Broadcast 60 0:01:04.892 0.050.642 02/27/2001 03:46:18 PM ARP: C PA=[209.215.49.87] PRO=IP
16 Sonic 0FC0F5 Broadcast 60 0:02:09.583 64.690.781 02/27/2001 03:47:23 PM ARP: C PA=[209.215.49.87] PRO=IP
17 [216.78.192.97] [207.18.xx.xx] 252 0:02:09.584 0.001.053 02/27/2001 03:47:23 PM UDP: D=514 S=15042 LEN=218
If the SonicWall is rebooted, theDHCP Renew process completes successfuly. But as you can see from the following packets, upon bootup, the SonicWall is sending the DHCP Renew request as a *broadcast* (to IP 255.255.255.255) vs. attempting to send it directly to the DHCP server (unicast). This is why the results are different after a reboot.
My question to SonicWall is this:
When issuing the DHCP Renew request why do you attempt to ARP for the DHCP server's IP address, when you know it's on a remote subnet?
Instead, you should be sending an ARP for the Default Gateway and simply forwarding the request to it. Alternately, you should simply broadcast the DHCP Renew request as you do on bootup.