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Old 05-21-2015, 01:35 PM   #1
lavanya87
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Registered: May 2015
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udhcpc client not recieving dchp offer from the dhcp server


Hi All,

I am using a udhcpc client from busybox to obtain IP addresses from the a isc-dhcpd server. Both are running in same network. I can see the dhcp discover messages from the tcpdump on the client machine and the server receiving this. The server responds with dhcp offer messages, but i do not see these messages reaching the client. I am not able to figure out the issue. Kindly help!!

Thanks,
Lavanya
 
Old 05-21-2015, 07:25 PM   #2
Ser Olmy
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Both DHCP Discovers and DHCP Offers are L3 broadcasts (destination IP address 255.255.255.255), and that should translate to an Ethernet broadcast (destination MAC address ff:ff:ff:ff:ff:ff). If one of them gets through, so should the other.

You are absolutely certain that the server is responding? You've seen the packet exiting the correct interface, destined for "255.255.255.255"/"ff:ff:ff:ff:ff:ff"? And it still doesn't appear at the client end? If so, you should check your switch(es) and cabling.
 
Old 07-20-2015, 10:40 AM   #3
sdetweil
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Registered: Jul 2015
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the problem is that the container is using a different mac address than the host machine.. and the host machine network stack will not respond to the unknown mac address..

to make this work, the host machine network interface must be set to promiscuous mode on, command ip link dev interface_name set promisc on.

if your host is running under a VMWARE product you must run the VMWARE (workstation/..) in admin mode to make this work. (you will not get any error from the ip link command, but it just will not work).

see the doc with the github pipework project on this issue.. (which uses a busybox container to run the udhcpc client)

I ran into the same thing, currently trying to get this to work on amazon AWS.
 
  


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