Data Networking/Spring 2016/Spartans
Group Members
edit- Amey Uchagaonkar
- Sooraj Shetty
- Thiyagarajan Anandan
This project is about integrating and make different components work together in the network. Four network components: Domain Name Server, Dynamic Host Configuration Protocol, Web server/ Firewall, Backup/ Client – are created on four virtual machines.
Steps:
1. Client takes an IP address from the DHCP server.
2. Client makes a page request, request proceeds to DNS for look up.
3. DNS resolves the IP address/Name and request is send to web server.
4. Web server sends back the requested page to client.
Working of Protocols
editDomain Name System (DNS)
DNS is used to translate IP address to hostname and vice versa. Rather than implementing centralized architecture for DNS, which creates a possibility of single point of failure, DNS is implemented in hierarchy. At the top of hierarchy are the root DNS servers, then comes the Top Level Domain (TLDs) and then authoritative DNS servers.
Client first invokes the host side of DNS to request IP for a hostname. Local DNS then contacts root server for query. Root server forwards information about all the TLD servers after looking at the suffix. TLD then directs local DNS to the authoritative server responsible for that hostname.
Dynamic Host Control Protocol (DHCP)
DHCP is used to allocate IP addresses to various hosts connected in a network. It automatically assigns IP addresses to all the hosts in the network of a specified range, a proper subnet mask, gateway, and DNS server of the network.
Firewall
Firewalls are used to avoid unauthorized access to our network i.e. we can control incoming and outgoing traffic of our organization using firewalls. Firewall filters the packets on the basis of either Source IP, Destination IP, Port or all of them.
Backup
It is a server used to back up all the data of a particular host, generally a web server or the whole network. It can also back up the required data to a different location, so that the data can be retrieved in case of failure of even back-up server.
Domain Name System (DNS)
editCommands Used
Installing DNS
Step 1 : To change the interface settings-
sudo nano /etc/network/interfaces
auto eth0
iface eth0 inet static
address 10.0.0.2
netmast 255.255.255.0
network 10.0.0.0
broadcast 10.0.0.255
Step2 : Install BIND9 which is used to implement DNS
sudo apt-get install bind9
Step3 : Include the Ips of Google public DNS servers in the forwarders section.
sudo nano named.conf.options
Remove the // comments and include 8.8.8.8 and 8.8.4.4
Step4 : Write the entries of forward and reverse lookup zones in named.conf.local file
Define these zones in both master and slave machines
#FORWARD LOOKUP ZONE - Holds A records, map hostnames to IPs
In the forward lookup zone write the following commands:
zone "spartans.com" { zone "spartans.com" {
type master; type slave;
file "/etc/bind/spartans.com.db"; masters { IP of master; };
allow-transfer { IP of slave; }; file "/var/cache/bind/db.spartans.com";
}; };
In the reverse lookup zone write the following commands
zone "0.0.10.in-addr.arpa" { zone "0.0.10.in-addr.arpa" {
type master; type slave;
allow-transfer {IP of slave; }; masters { IP of master; };
file "/etc/bind/0.0.10.in-addr.arpa"; file "/var/cache/bind/db.spartans.rev";
}; };
For IPv6 write the following commands
zone "0.0.0.0.0.0.0.0.0.0.0.0.0.8.e.f.ipv6.arpa" {
type master;
notify no;
};
Step5 : Forward look-up zone
@ IN SOA spartans.com. admin.spartans.com. (
2007031001;
28800;
3600;
604800;
38400;
);
@ IN NS spartans.com.
@ IN A 10.0.0.3
Step6 : Reverse Look-up zone file
$TTL 3D
$TTL 3D
@ IN SOA spartans.com. admin.spartans.com. (
2007031001;
28800;
3600;
604800;
38400;
);
@ IN NS spartans.com.
3 IN PTR spartans.com.
Step7 : Make changes to resolv.conf
search spartans.com
nameserver 10.0.0.3
Step8 : To make the changes effective, restart bind9
sudo /etc/init.d/bind9 restart
Dynamic Host Control Protocol (DHCP)
editStep 1 : Installing DHCP
sudo apt-get install isc-dhcp-server
Step 2 :Edit the interface file
sudo nano /etc/network/interfaces
auto eth0 #interface configuration
iface eth0 inet static
address 10.0.0.1
netmask 255.0.0.0
network 10.0.0.0
broadcast 10.0.0.255
Step 3 : Restart with the new config
sudo nano /etc/init.d/networking restart
Step 4 : Edit dhcpd conf file/set range and other paramteres
sudo nano /etc/dhcp/dhcpd.conf
default-lease-time 600;
max-lease-time 7200;
option subnet-mask 255.0.0.0;
option broadcast-address 10.0.0.255;
#option domain-name-servers 10.0.0.2;
option domain-name "spartans.com";
subnet 10.0.0.0 netmask 255.0.0.0 {
range 10.0.0.10 10.0.0.100;
}
host dns {
hardware ethernet 00:0c:29:5e:72:3c;
fixed-address 10.0.0.2;
}
host webserver {
hardware ethernet 00:0c:29:c7:ea:81;
fixed-address 10.0.0.3;
}
Step 6 : Restart DHCP
Webserver
editStep1 : Install apache2 web server
sudo apt-get install apache2
Step2 : To check if webserver is listening on which port
Netstat –a |more
Netstat – an | more
Step3 : Restart the web server
sudo /etc/init.d/apache2 stop
sudo /etc/init.d/apache2 start
Step4 : To put the webpage on the server
cd /var/www
www$ sudo nano index.html
Firewall
editStep1 : Block a host to telnet into webserver
sudo ufw deny telnet
Step2 : Allow a host to Web request
sudo ufw allow 80
Backup
editIn order for a Linux Web server to automate our task of sending backup, we need an automatic login from our web server to host on which the backup is being copied. We don't want to enter any password.
Step1 : Log onto web server and generate a pair of authentication keys
sudo ssh-keygen -t rsa
Step2 : Now use ssh to create a directory ~/.ssh on the host machine.
ssh linuxhost@10.0.0.10 mkdir -p .ssh
Step3 : Finally append Web server's public key to host
cat .ssh/id_rsa.pub | ssh linuxhost@10.0.0.10 'cat >> .ssh/authorized_keys'
Step4 :Now we will compress the file that we need to make the backup
sudo tar -cvpzf minutebackup.tar.gz /var/www/html/index.html
Step5 :Using the cron jobs we will schedule the backup for every minute
sudo crontab -e
* * * * * sudo tar -cvpzf /home/pratik/backupfolder/minutebackup.tar.gz /var/www/html/index.html
* * * * * sudo scp /home/pratik/backupfolder/minutebackup.tar.gz linuxhost@10.0.0.10:
Mail Server
editStep1 : Install the postfix package first with defaults
sudo apt-get install postfix
Step 2 : Detailed configuration is done here. Select Internet Site as General type of mail config. System mail name -> FQDN name. Define the local Networks.
sudo dpkg-reconfigure postfix
Step 3 : Edit edit /etc/postfix/sasl/smtpd.conf file and put these lines in it.
pwcheck_method: saslauthd
mech_list: plain login
Step 4 :Restart postfix daemon
sudo /etc/init.d/postfix restart
Testing
edit
Testing DNS
We basically use nslookup command to test DNS. Try nslookup <hostname> from all PCs in the network and it should show the translated IP. Also test reverse lookup. Apart from nslookup we can also use dig, host commands to test DNS.
Testing DHCP
Connect client PC to the network and it should be assigned with a IP address automatically. This can be checked by ifconfig.
Testing WebServer
Test by entrring hostname or IP address in any web browser.
Testing Firewall
Telnet to webserver is blocked. Try to telnet its Ip and it should show timeout.
Testing backup
Check the backup file on destination location by typing ls -l command and check the time when the last file backup was done.
Future Improvements
edit1)Digital Signatures, symmetric key encryption, authentication can provide extra security to DNS.
2)Using DHCP to assign IP address for different subnets. This is possible with the use of relay agents.
3)Dynamic DNS helps to update records with dynamic IP address.
Citations
editWebsites
1. https://help.ubuntu.com/community/BIND9ServerHowto
2. https://help.ubuntu.com/lts/serverguide/dns-configuration.html
3. http://www.ubuntugeek.com/how-to-install-and-configure-dhcp-server-in-ubuntu-server.html
4. https://help.ubuntu.com/community/isc-dhcp-server
5. https://www.digitalocean.com/community/tutorials/how-to-set-up-a-firewall-using-iptables-on-ubuntu-14-04
6. https://wiki.ubuntu.com/BasicSecurity/Firewall
7. http://www.server-world.info/en/note?os=Ubuntu_12.04&p=nis&f=2
8. http://net.tutsplus.com/tutorials/other/the-linux-firewall
9. https://help.ubuntu.com/community/PPTPServer
Books Referred
1. Computer Networking: A Top-Down Approach, James F. Kurose, Keith W. Ross