Trisul Network Analytics
Developer Zone

**This is an old revision of the document!** ----

====== How to redirect Netflow to Trisul across network segments using NAT ====== In some customers, Trisul is on a separate segment from the production routers. These sites often have a gateway device that be be used to access. The routers can each the gateway to export NETFLOW but cannot reach the Trisul server. The picture below shows how the setup is. {{:hardware:netflow-nat.png?600|}} This HOWTO explains how to use Linux IPTABLES NAT to move between the two. ===== IPTABLES Port based NAT ===== On the gateway device you just need to run the following commands, say you want to move port 2055 to a particular IP. ==== Shutdown ufw or disable firewalld ==== <code bash> # On Ubuntu ufw disable # On CentOS/RHEL systemctl firewalld stop # Make sure ip forwarding is enabled in kernel echo 1 > /proc/sys/net/ipv4/ip_forwarding </code> ==== Then setup the Port NAT ==== The following commands move port 2055 to the Trisul IP (see the diagram above) . <code> $ iptables -t nat -A PREROUTING -p udp \ --dport 2055 -j DNAT --to-destination 10.10.10.17:2055 </code> You should now be seeing Netflow flowing to the Trisul box. <note important>NOTE: Do not use the MASQUERADE POSTROUTING rule, because we want to preserve the IP address of the original router in the netflow packets. Otherwise Trisul can assume that the Gateway device is the router. </note> ==== Useful commands ==== To view NAT rules with counters '' iptables -t nat -vL '' ==== Reference ==== How to redirect incoming traffic on a port to another IP https://my.esecuredata.com/index.php?/knowledgebase/article/49/how-to-redirect-an-incoming-connection-to-a-different-ip-address-on-a-specific-port-using-iptables/