Dnsmasq is a simple way to set up a DNS server for a small network, rather than going to the trouble of configuring BIND.
Add Network Cards
Network Topology
IP Configuration
Dnsmasq Installation
Dnsmasq Configuration
Verification
Add Network Cards
- In my articles for RAC, I usually use three network cards for each of my nodes with following settings on VirtualBox
- In Network window, under Adapter 1, select Bridged Adapter for Public RAC interface
- In Network window, under Adapter 2, select Internal Network for Private RAC interface
- In Network window, under Adapter 3, select NAT for Internet connection
Network Topology
The planned addresses, hostnames and their purpose:
IP Configuration
Right-Click network Icon on task bar and select Edit Connections
Select System eth0 -> Edit
Check Connect automatically
Click tab IPv4 Settings
Select Method to Manual from drop down list, then click Add and fill the following fields:
Address: 192.168.0.101, Netmask: 255.255.255.0, Gateway: 192.168.0.1, DNS Servers: 127.0.0.1, Search domains: oracleapps.com
Click Apply
Select System eth1 -> Edit then Check Connect automatically
Click tab IPv4 Settings
Select Method to Manual from drop down list, then click Add and fill the following fields:
Address: 192.168.1.101, Netmask: 255.255.255.0, Gateway: 192.168.1.1, DNS Servers: 127.0.0.1, Search domains: oracleapps.com
Click Apply
Go to Terminal and restart the network services
The Dnsmasq service is installed from a Yum repository using the following command:
The service can be stopped, started and restarted using the following commands.
You don't need to do any specific DNS configuration as Dnsmasq will use the contents of the "/etc/hosts" to resolve any name requests. Anything it can't find there will be forwarded to the nameservers listed in the "/etc/resolv.conf" file.
Adding the following entries to the "/etc/hosts" file on the server running Dnsmasq, will allow it to act as a DNS, resolving those names.
Once everything is setup, now test the IP lookup with nslookup command:
Network Topology
IP Configuration
Dnsmasq Installation
Dnsmasq Configuration
Verification
Add Network Cards
- In my articles for RAC, I usually use three network cards for each of my nodes with following settings on VirtualBox
- In Network window, under Adapter 1, select Bridged Adapter for Public RAC interface
- In Network window, under Adapter 2, select Internal Network for Private RAC interface
- In Network window, under Adapter 3, select NAT for Internet connection
Network Topology
The planned addresses, hostnames and their purpose:
| IP Address | Host Name | Description |
|---|---|---|
| 192.168.0.101 | rac1.oracleapps.com | Public address of first node |
| 192.168.0.102 | rac2.oracleapps.com | Public address of second node |
| 192.168.0.111 | rac1-vip.oracleapps.com | Virtual address of first node |
| 192.168.0.112 | rac2-vip.oracleapps.com | Virtual address of second node |
| 192.168.1.101 | rac1-priv.oracleapps.com | Private address of first node |
| 192.168.1.102 | rac2-priv.oracleapps.com | Private address of second node |
| 192.168.0.121 | rac-scan.oracleapps.com | SCAN address of cluster |
| 192.168.0.122 | rac-scan.oracleapps.com | SCAN address of cluster |
| 192.168.0.123 | rac-scan.oracleapps.com | SCAN address of cluster |
IP Configuration
Right-Click network Icon on task bar and select Edit Connections
Select System eth0 -> Edit
Check Connect automatically
Click tab IPv4 Settings
Select Method to Manual from drop down list, then click Add and fill the following fields:
Address: 192.168.0.101, Netmask: 255.255.255.0, Gateway: 192.168.0.1, DNS Servers: 127.0.0.1, Search domains: oracleapps.com
Click Apply
Select System eth1 -> Edit then Check Connect automatically
Click tab IPv4 Settings
Select Method to Manual from drop down list, then click Add and fill the following fields:
Address: 192.168.1.101, Netmask: 255.255.255.0, Gateway: 192.168.1.1, DNS Servers: 127.0.0.1, Search domains: oracleapps.com
Click Apply
Go to Terminal and restart the network services
# service network restartDnsmasq Installation
The Dnsmasq service is installed from a Yum repository using the following command:
# yum install dnsmasqTurn on the Dnsmasq server and make sure it starts automatically on reboot.
# service dnsmasq start # chkconfig dnsmasq onDnsmasq is configured by altering the contents of the "/etc/dnsmasq.conf" file and the contents of the "/etc/hosts" file.
The service can be stopped, started and restarted using the following commands.
# service dnsmasq stop # service dnsmasq start # service dnsmasq restartDnsmasq Configuration
You don't need to do any specific DNS configuration as Dnsmasq will use the contents of the "/etc/hosts" to resolve any name requests. Anything it can't find there will be forwarded to the nameservers listed in the "/etc/resolv.conf" file.
Adding the following entries to the "/etc/hosts" file on the server running Dnsmasq, will allow it to act as a DNS, resolving those names.
192.168.0.101 rac1.oracleapps.com rac1 192.168.0.102 rac2.oracleapps.com rac2 192.168.0.111 rac1-vip.oracleapps.com rac1-vip 192.168.0.112 rac2-vip.oracleapps.com rac2-vip 192.168.1.101 rac1-priv.oracleapps.com rac1-priv 192.168.1.102 rac2-priv.oracleapps.com rac2-priv 192.168.0.121 rac-scan.oracleapps.com rac-scan 192.168.0.122 rac-scan.oracleapps.com rac-scan 192.168.0.123 rac-scan.oracleapps.com rac-scanI’m using third network card as NAT with DHCP (For Internet) so each time you restart network card or reboot the server, the file /etc/resolv.conf is overwritten with automatically generated settings. Nameserver points for 192.168.0.1 which is required to resolve internet entries but not enough to resolve SCAN settings via dnsmasq.
# cat /etc/resolv.conf # Generated by Networkmanager nameserver 127.0.0.1 search oracleapps.com nameserver 192.168.0.1You must lock the file from being automatically overwritten by server reboot, network card restart etc.
# chattr +i /etc/resolv.confVerification
Once everything is setup, now test the IP lookup with nslookup command:
# nslookup rac1 Server: 127.0.0.1 Address: 127.0.0.1#53 Name: rac1.oracleapps.com Address: 192.168.0.101 # nslookup rac2 Server: 127.0.0.1 Address: 127.0.0.1#53 Name: rac2.oracleapps.com Address: 192.168.0.102 # nslookup rac1-priv Server: 127.0.0.1 Address: 127.0.0.1#53 Name: rac1-priv.oracleapps.com Address: 192.168.1.101 # nslookup ebsrac-scan Server: 127.0.0.1 Address: 127.0.0.1#53 Name: ebsrac-scan.oracleapps.com Address: 192.168.0.123 Name: ebsrac-scan.oracleapps.com Address: 192.168.0.121 Name: ebsrac-scan.oracleapps.com Address: 192.168.0.122 # nslookup ebsrac-scan Server: 127.0.0.1 Address: 127.0.0.1#53 Name: ebsrac-scan.oracleapps.com Address: 192.168.0.121 Name: ebsrac-scan.oracleapps.com Address: 192.168.0.122 Name: ebsrac-scan.oracleapps.com Address: 192.168.0.123You need to do all the above settings and configure dnsmasq on each node of the cluster.
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