On 6/27/2007 1:12 AM Alan McKinnon said the following:
On Wednesday 27 June 2007, Randy Barlow wrote:
Drew Tomlinson wrote:
I ran tcpdump on eth1 and no packets are leaving the interface.
Thus I assume that's why I'm not getting an address.
I don't know how to solve your problem, but I don't think DHCP is at
the TCP layer of your network, and so you shouldn't see packets for
DHCP there. DHCP is a special protocol if I recall...
That's correct, dhcp is an ethernet protocol, and tcp/ip are one layer
above it.
Drew should be able to see the packets with the 'proto ether'
expression.
man tcpdump for more info
alan
Thank you both for your ideas. I've tested and it seems that I should
be able to see the packets without any special expressions. I've run
tcpdump on my DHCP server and can see packets from other nodes on my
network:
Client IP: bigdaddy
Client Ethernet Address: 00:50:8d:d7:8d:89 (oui Unknown) [|bootp]
15:39:48.229850 IP (tos 0x0, ttl 128, id 25950, offset 0, flags [none],
proto: UDP (17), length: 328) bigdaddy.bootpc > 255.255.255.255.bootps:
BOOTP/DHCP, Request from 00:50:8d:d7:8d:89 (oui Unknown), length: 300,
xid:0x7707a3b2, secs:768, flags: [none]
When I run 'tcpdump -i eth1' on the laptop, I see no traffic
whatsoever. I read the man page for tcpdump regarding the 'proto ether'
expression Alan mentions. While it is true that this expression will
limit the traffic captured, not specifying any expression will show all
traffic. Plus DHCP works by sending UDP packets and thus 'proto ether'
does not seem to be appropriate.
Thanks,
Drew
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