![Introduction IP Internet has had two most significant problems: ,[object Object],[object Object],[object Object],The first short-term solution was: Two types of solutions proposed: short-term and long-term](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
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Nad710 Network Address Translation
- 1. NAD710 - Introduction to Networks Using Linux Network Address Translation May 28, 2003 Professor Tom Mavroidis
- 3. The long-term solutions consist of various proposals for new Internet protocols with larger addresses (IPv6) When CIDR failed to further maintain the IP internet structure, there came another proposal : N A T NAT is not a very far reaching or long term solution But at least it is very fast, provides extra time until better solutions are designed and almost independent from the outer networks. Proposals
- 5. NAT is translation of either a subset or all of the IP addresses in a sub domain to globally unique address(es). From an operational point of view, it is a function imposed on the router. That is a router on the gateway border to be configured as a Network Address Translator. What is NAT?
- 9. IP chains flow of events: Local processes CRC INPUT chain Inbound packet OK Malformed? garbage yes error Deny-reject Accept packet Routing algorithm Local destination Outbound packet Malformed? forwarded packet no no FORWARD chain Deny-reject yes Malformed? yes Outbound packet no OUTPUT chain Deny-reject Outbound packet
- 10. Enable IP forwarding for the kernel Execute: echo “1” > /proc/sys/net/ipv4/ip_forward Or make it permanent ( persistent between boots ) with assigning the variable IP_FORWARD = yes in /etc/sysconfig/sysctl file This will ensure basic router functionality Use /sbin/ipchains-save > afilename to save the rules Use /sbin/ipchains-restore < afilename to restore the rules To get this thing going
- 11. IP chains syntax ipchains –[flags] [input | outout | forward | custom_chain] [options] [action] ipchains –M [-L | -S] [options] A very simple example with IP Masquerading: ROUTER WITH NAT 10.1.1.1 eth1 202.7.1.19 eth0 Internet Internal net 10.0.0.0
- 16. IP tables syntax iptables –[flags] [chain] [options [extentions] ] [action] Syntax and examples: A very simple example with Static IP Translation: ROUTER WITH NAT 10.1.1.1 eth1 202.7.1.19 eth0 www ftp 10.1.1.4 10.1.1.5 Internet Internal net 10.0.0.0/8
- 17. 192.168.0.1 192.168.0.14 192.168.1.15 192.168.0 192.168.1 192.168.1.13 192.168.0.16 192.168.1.16 RedHat 6.2 RedHat 6.2 ROUTER running SuSE 8.0 Windows 98 Windows 98 10 mb/s repeater 100 mb/s switch
- 18. 192.168.0.1 192.168.0.14 192.168.1.15 ROUTER with NAT running SuSE 8.0 192.168.0 192.168.1 192.168.1.13 192.168.0.16 192.168.0.15 192.168.0.13 192.168.1.16 internet Windows 98 with NAT ppp RedHat 6.2 RedHat 6.2 Windows 98 100 mb/s switch 10 mb/s repeater