How To DHCP on a Private Network with VM's :

How To DHCP on a Private Network with VM's :
====================================

Hypervisor : - Hypervisor-Host

DHCP Client : - Host-DHCP-Client

DHCP Server : Host-DHCP-Server

DHCP server:(Imp files/command)
Config file : /etc/dhcpd.conf
Pid file :  : /var/run/dhcpd.pid

The DHCP daemon can be configured with command line options by using the /etc/sysconfig/dhcpd file.
For security, DHCP can be bound to an interface so the allocation of addresses are only available to the private internal network
# cat /etc/sysconfig/dhcpd
# Command line options here
DHCPDARGS=eth0




DHCP client :(Imp files/commands)
/var/lib/dhclient/dhclient-eth0.leases ( To check lease obtained)

[root@Host-DHCP-Client ~]# ps -elf |grep dhclient
1 S root      1509     1  0  75   0 -  1692 -      19:45 ?        00:00:00 /sbin/dhclient -1 -q -lf /var/lib/dhclient/dhclient-eth0.leases -pf /var/run/dhclient-eth0.pid eth0



For Dhcp Client vm.cfg under Hypervisor:

/var/ovs/mount/70B7E79628294FF8A7C92D6EFCD506FA/running_pool/2374_Host-DHCP-Client

Add the below line :
--------------------------------------------------------------
dhcp = "dhcp"
vif = ['bridge=xenbr0,mac=00:16:3E:48:E1:3E,type=netfront']
--------------------------------------------------------------


mac addres is the address of eth0 in dhcp client Host-DHCP-Client

Started vm again
bash$xm create ./vm.cfg




Configuration in DHCP server :
=============================

1) Edit /etc/dhcpd.conf

[aime1@crm-ohs dhcpd]$ cat /etc/dhcpd.conf
ddns-update-style none;
#local7.* /var/log/dhcpd.log;
option domain-name-servers 144.20.190.70, 138.2.202.15, 130.35.249.41;

default-lease-time 86400;
max-lease-time 604800;

authoritative;

subnet 192.168.1.0 netmask 255.255.255.0 {
#        interface eth0:1;
        range 192.168.1.128 192.168.1.254;
         option subnet-mask  255.255.255.0;
        option broadcast-address 192.168.1.255;
#        option routers 192.168.1.10;

}
[aime1@crm-ohs dhcpd]$



2) start dhcp server

dhcpd eth0

Please Note dhcp runs only on eth0 or eth1 and it wont run on aliases like eth0:1

3) Check the status :

[root@crm-ohs ~]# /etc/rc.d/init.d/dhcpd status
dhcpd (pid  17607) is running...
[root@crm-ohs ~]#

4)  Added a (Virtual IP just to check )

$ifconfig eth0:1 192.168.1.10 netmask 255.255.255.0 up


eth0:1    Link encap:Ethernet  HWaddr 00:16:3E:41:46:00 
          inet addr:192.168.1.10  Bcast:192.168.1.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1



Configuration in DHCP Client :
==============================

1)

[root@Host-DHCP-Client ~]# cat /etc/sysconfig/network-scripts/ifcfg-eth0
# Xen Virtual Ethernet
DEVICE=eth0
ONBOOT=yes
BOOTPROTO=dhcp
[root@Host-DHCP-Client ~]#


2) restart network (or better reboot host)

/etc/rc.d/int.d/network restart

3) Now chekc the Ip obtained is in 192 series :

[root@Host-DHCP-Client ~]# ifconfig
eth0      Link encap:Ethernet  HWaddr 00:16:3E:48:E1:3E 
          inet addr:192.168.1.254  Bcast:192.168.1.255  Mask:255.255.255.0
          inet6 addr: fe80::216:3eff:fe48:e13e/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:377865 errors:0 dropped:0 overruns:0 frame:0
          TX packets:12622 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:91226762 (87.0 MiB)  TX bytes:8154809 (7.7 MiB)