Re: [lwip-users] No Reply to DHCP Discover

[Ben Rector]

I compared this frame with the one that my windows box makes. Everything is the same except for the options (windows uses more options) and the padding (windows has less padding) and my packet ends up being longer. I put a break point in my low level transmit, and the pbuf that is being transmitted has the same length as what actually gets transmitted.  The options that lwIP is requesting are:

1 subnet mask

3 router

28 broadcast address

6 domain name server

also, after I see a few discover requested by my device (using lwIP) I start seeing an ARP request immediatly following the discover request, it is the router asking who is at 192.168.1.3, but no one is assigned that address.

On Thu, Oct 4, 2012 at 11:28 PM, Ben Rector <address@hidden> wrote:

I have been using lwIP with a static IP address, and I have gotten things up and working and my driver appears to be doing ok (things in wire shark look good). I wan't to switch to DHCP to simplify things and to obtain the DNS serves from my gateway. However, I am never assigned an IP address. I can see the DHCP Discover packet transmitted by lwIP to my Netgear router, but I don't get an offer, or even a NAK. lwIP just keeps sending out Discover packets. Any thoughts or clues? I followed the example on the WIKI, and I think I am doing it right. Any help would be greatly appreciated.

I know it is low level, but here is the output of the wire shark packet if it is of any help:

Source: 0.0.0.0     Dest: 255.255.255.255  Prot:DHCP    Lenght: 350    Info: DHCP Discover - Transaction ID 0xabcd001

0000  ff ff ff ff ff ff 00 60  37 00 12 34 08 00 45 00   .......` 7..4..E.

0010  01 50 00 20 00 00 ff 11  ba 7d 00 00 00 00 ff ff   .P. .... .}......

0020  ff ff 00 44 00 43 01 3c  27 13 01 01 06 00 ab cd   ...D.C.< '.......

0030  00 01 00 00 00 00 00 00  00 00 00 00 00 00 00 00   ........ ........

0040  00 00 00 00 00 00 00 60  37 00 12 34 00 00 00 00   .......` 7..4....

0050  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00   ........ ........

0060  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00   ........ ........

0070  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00   ........ ........

0080  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00   ........ ........

0090  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00   ........ ........

00a0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00   ........ ........

00b0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00   ........ ........

00c0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00   ........ ........

00d0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00   ........ ........

00e0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00   ........ ........

00f0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00   ........ ........

0100  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00   ........ ........

0110  00 00 00 00 00 00 63 82  53 63 35 01 01 39 02 05   ......c. Sc5..9..

0120  dc 37 04 01 03 1c 06 ff  00 00 00 00 00 00 00 00   .7...... ........

0130  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00   ........ ........

0140  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00   ........ ........

0150  00 00 00 00 00 00 00 00  00 00 00 00 00 00