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F5 BIG-IP – Apply SNAT to client subnet or IP Posted on August 17, 2017

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1 Create a SNAT pool 2 Create IRULE

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3 Assign IRULE to POOL

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4 Check IRULE is working correctly 4.1 Command “show sys conn” 4.2 Log file /var/log/LTM

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Assign name and iP(s) to use as translated source IP

Windows

Create IRULE Before crea ng the IRULE we need to know 3 “values”: – client IP(s) to which we want to apply the SNAT – Name of the virtual server POOL of the virtual server we want the SNAT to apply to – Name of the SNAT POOL created on the previous step Local Traffic – IRules – IRule List –

Assign name and set the following code (in red my own example values. Replace them with yours)

when CLIENT_ACCEPTED { log local0. "client:" if { [IP::client_addr] contains "192.168.190." } { pool POOL_EXCHANGE snatpool SNAT_POOL_LAN } }

Assign IRULE to POOL Local Traffic – Virtual Servers – Virtual Server List – <Select VS> – Resources Assign the newly created IRule in the IRules sec on

Check IRULE is working correctly Command “show sys conn” By using the “show sys conn” TMSH command you can check ac ve connec on (filtering by virtual server IP for example). For example, my VS_EXCHANGE virtual server has an 192.168.206.233 IP. To check the connec ons:

# tmsh show sys conn cs-server-addr 192.168.206.233%1

The ouput shows: <server IP>

As you can see, when the client IP does not contain “192.168.190.”, the IP is not translated. However, the “192.168.190.126” client IP was translated to the one defined in the SNAT pool (192.168.190.250).

Log file /var/log/LTM /var/log/ltm file can also show if the IRule is being applied:

# tail -f /var/log/ltm | grep IRULE_SNAT_EXCHANGE Aug 17 10:24:05 BigIP1 info tmm3[28767]: Rule /LAN/IRULE_SNAT_EXCHANGE : client: Aug 17 10:24:05 BigIP1 info tmm2[28767]: Rule /LAN/IRULE_SNAT_EXCHANGE : client:

This entry was posted in F5 BIG-IP and tagged bigip, F5, howto, nat, T/IP by Sys SomoIT. Bookmark the permalink.

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