1. Managing and Directing Network Traffic with Linux
Oscar Mederos

2. Network Architecture
Networks are interconnected through routers and gateways
A router interconnects 2 networks
A gateway defines the start of a network
All gateways are routers, not all routers are gateways

3. TCP/IP traffic routing in Linux
Edit /etc/sysctl.conf & uncomment net.ipv4.ip_forward=1
Your computer can now route packets!
Define your interfaces in /etc/networking/interfaces
Set eth0 to dhcp, eth1 to static & assign it an IP

4. Kernel modules Enable the following kernel modules ip_tables
nf_conntrack
nf_conntrack_ftp
iptable_nat
nf_nat_ftp

5. IP chains & the gateway
Set IP chains to NAT packets & allow traffic re- direction from eth0 to eth1
-A POSTROUTING -o "eth1" -j MASQUERADE
-A FORWARD -i "eth0" -o "eth1" -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT
-A FORWARD -i "eth0" -o "eth1" -j ACCEPT
-A FORWARD -j LOG

6. Host configurations In linux route add default gw *eth1 IP
In windows visit your connection settings for tcp/ip and point your gateway to the IP of the linux host we just set up as a gateway
All hosts must have IP addresses on the same network as the router's internal network interface

8. Quagga
Quagga is a network routing software suite providing implementations of Open Shortest Path First (OSPF), Routing Information Protocol (RIP), Border Gateway Protocol (BGP)

9. Quagga
The Quagga architecture consists of a core daemon (zebra) which is an abstraction layer to the underlying Unix kernel and presents the Zserv API over a Unix-domain socket or TCP socket to Quagga clients. The Zserv clients typically implement a routing protocol and communicate routing updates to the zebra daemon.