how to change isc-dhcp3-server replies?

Joe josepha48 at yahoo.com
Sun Sep 2 16:02:01 PDT 2007


For some reason they are no longer showing up in tcpdump?

I can see the DHCP discover and the DHCP offers, but can't get tcpdump to output them?

DHCPDISCOVER from AA:AA:AA:AA:AA:AA via xl0
DHCPOFFER on 192.168.0.13 to AA:AA:AA:AA:AA:AA (w2k-box) via xl0

This happens 4 times, but I can get tcpdump to output the offer.  Using

tcpdump -netvvvi xl0 -t udp port 67 or udp port 68

Not sure what is going on now.  

Joe

    > Ok, no so true. I am watching tcpdump output from the two binaries. The
    > old binary sends its reply to 255.255.255.255, while the new one sends its
    > reply to 192.168.0.15. Same config file and I tried the always-broadcast
    > flag, and it only sets the bit for the client, but the server still
    > broadcasts its reply to the client on the subnet mask.
    >
    > Old client reply (ml.. is server af is client):
    >
    > 1188694380.961642 ml:ml:ml:ml:ml:ml > ff:ff:ff:ff:ff:ff, ethertype IPv4
    > (0x0800), length 342: (tos 0x10, ttl 16, id 0, offset 0, flags [none],
    > proto: UDP (17), length: 328) 192.168.0.15.67 > 255.255.255.255.68:
    > BOOTP/DHCP, Reply, length: 300, xid:0x77915dc3, flags: [Broadcast] (0x8000)
    > Your IP: 192.168.0.13
    > Client Ethernet Address: af:af:af:af:af:af [|bootp]
    >
    > new client does not do this and clients do not get their ip address. I read
    > somewhere that linux had a problem doing this in 2.2 kernels and it has
    > something to do with the routing table in linux. Not sure what is going on
    > here, but the routing table looks fine.

    So what does the tcpdump exchange look like with the new binary and the
    always-broadcast flag? And we're talking server binaries, right?


       
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