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--- hardware:shimtunnel [2019/01/10 20:16] – [Run the nfshim server on the gateway node] veera
+++ hardware:shimtunnel [2019/01/11 18:16] (current) – veera
@@ Line 13: / Line 13: @@
   * Gateway Node real IP : 192.169.2.81 (both should be able to ping each other)
   * Port used : UDP 5111
+  * Source IP to use on the gateway end of shim tunnel : 10.251.52.4
+<note warning>
+**Pre-check**
+  * ensure IP Forwarding is disabled ''echo 0 > /proc/sys/net/ipv4/ip_forward''
+  * local iptables firewall rules allow the UDP port ''iptables -A INPUT -p udp -m udp --dport 5111 -j ACCEPT''
+</note>
 ===== Download the Shim software =====
@@ Line 20: / Line 27: @@
 Visit https://github.com/trisulnsm/netflow-shim-tunnel/tree/master/binaries and download the binary for your platform.
-Example
 <code>
@@ Line 45: / Line 50: @@
 <code>
 chmod +x nfshim.el7
-./nfshim.el7  -D 0.0.0.0:5111  192.168.2.99:5111 10.259.52.4
+./nfshim.el7  -D 0.0.0.0:5111  192.168.2.99:5111 10.251.52.4
 </code>
@@ Line 66: / Line 71: @@
 Restart  Trisul. You should now be able to see the Netflow analysis on the Trisul node with the actual router/switch IP addresses.
+===== Extra reference : Use Source NAT =====
+In the very unlikely scenario the above steps dont work and the desired source IP is not seen on the outgoing packets, use SNAT (Source NAT).This example NATs the source IP for udp packets to 5111 (custom netflow)  to be the Shim end point.
+<code>
+iptables -t nat -A   POSTROUTING -p udp --dport 5111 \
+    -o enp7s0  -j SNAT --to 10.251.52.4:5111
+</code>
+==== To view rules ====
+<code>
+iptables -t nat -L -v --line-numbers
+</code>
+==== To delete a rule with id 3 ====
+<code>
+iptables -t nat -D POSTROUTING  3
+</code>