Can I SNAT UDP traffic using iRule? [for outbound traffic]

Yes you can, but you shouldn't need an iRule. Assuming you have a UDP VIP assigned to forward this traffic, assign a SNAT pool there.

Hi Kevin,

Thanks for the answer. However the VS is a forwarding VS for all protocols. We need to SNAT traffic specifically for outbound ICMP and SNMP connections.

Any help?

I would probably do something like this:

when CLIENT_ACCEPTED {
    switch [IP::protocol] {
        "1" -
        "17" {
            snat automap
        }
    }
}
when CLIENT_DATA {
    switch [IP::protocol] {
        "1" -
        "17" {
            snat automap
        }
    }
}

Thanks for this Kevin,

Do I need Client_Accepted and Client_Data both to be mapped within same iRule? I would need to add Client_IP_addr in Client_Accepted, right?

Thank you, Darshan

I would need to add Client_IP_addr in Client_Accepted, right?

Do you need to do this based on the client IP? I'm assuming not.

The above is one iRule that should be applied to the forwarding VIP. You need both the CLIENT_ACCEPTED and CLIENT_DATA events because UDP's statelessness won't always trigger a CLIENT_ACCEPTED event.

Sorry, I think I didn't explain the exact requirement.

I have 3 IP addresses which I want to SNAT, only for ICMP and SNMP for outbound connection.

I made a rule as following which doesn't seem effective, not sure why.

when CLIENT_ACCEPTED {
   if { ([IP::addr [IP::client_addr] equals 10.254.47.12/32] or [IP::addr [IP::client_addr] equals 10.254.47.13/32]) and [TCP::local_port] == 161 }{
      snat 10.254.55.65
   }
else
{
forward
}
}

Try this:

when CLIENT_ACCEPTED {
    if { ( [IP::addr [IP::client_addr] equals 10.254.47.12/32] or [IP::addr [IP::client_addr] equals 10.254.47.13/32] ) } {
        switch [IP::protocol] {
            "1" -
            "17" {
                snat automap
            }
        }
    }
}
when CLIENT_DATA {
    if { ( [IP::addr [IP::client_addr] equals 10.254.47.12/32] or [IP::addr [IP::client_addr] equals 10.254.47.13/32] ) } {
        switch [IP::protocol] {
            "1" -
            "17" {
                snat automap
            }
        }
    }
}

Perfect!

Thanks a ton!! Btw, where can I get the list of protocol number listed in your iRule?

http://www.iana.org/assignments/protocol-numbers/protocol-numbers.xml