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192.168.2.1(dhcp server) -> (eth1 192.168.2.3)[ubuntu 14.04 dhcp relay server](eth0 192.168.1.1) -> Client

isc-dhcp-relay successful installed, configuration file is

#/etc/default/isc-dhcp-relay
SERVERS="192.168.2.1"
INTERFACES="eth0 eth1"

SERVERS is the upstream dhcp server, using eth1. downstream goes to eth0. isc-dhcp-relay service is OK:

isc-dhcp-relay start/running, process 1480

but I can't get ip addr from client.

this is network config file on the dhcp relay server

#/etc/network/interfaces
auto eth1
iface eth1 inet dhcp

auto eth0
iface eth0 inet static
  address 192.168.1.1

I got this, when I let the client request ip addr, tcpdump -i eth1, this from relay server NIC connect to the main DHCP server. MAC address is the NIC on the client.

17:29:17.615478 IP 192.168.2.3.bootps > 192.168.2.1.bootps: BOOTP/DHCP, Request from 00:24:8c:57:e0:7e (oui Unknown), length 300

and tcpdump -i eth0, I got this:

17:38:34.022686 IP 0.0.0.0.bootpc > 255.255.255.255.bootps: BOOTP/DHCP, Request from 00:24:8c:57:e0:7e (oui Unknown), length 300

And "main dhcp server" (it actually is my macbook shared network) log file:

Mar  2 17:55:22 liaos-MacBook-Pro.local bootpd[90944]: DHCP DISCOVER [bridge100]: 1,0:24:8c:57:e0:7e <test>
  • DHCP server logs? Relay logs? Client logs? tcpdumps? – Mikel Mar 2 '15 at 8:29
  • Thanks @Mikel for reminding me about the tcpdump. I update my post so it is better for reading. Seems the request been transfer between two NICs – Liao Zhuodi Mar 2 '15 at 9:44

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