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Forum Discussion

Marcus_Hong_Yu's avatar
Marcus_Hong_Yu
Icon for Nimbostratus rankNimbostratus
Jun 13, 2017

RESOLV::lookup not able to pick resolved IP from DNS query answer

I recently used an irule on LTM to do DNS query for traffic forwarding. I used RESOLV::lookup in the irule to go against my DNS server and use resolved IP as pool member IP to establish the connectio...
application delivery
iRules
LTM
cjunior's avatar
cjunior
Icon for Nacreous rankNacreous
Jun 13, 2017

Marcus, I can't see why, in this vCMP case where you can peek on tcpdump, the iRule was empty for that responses.

Maybe by separating things, you could see where is the issue. In you log line, I see you are double checking dns.

Did you try it in separated lines before? 
when CLIENT_ACCEPTED {
    set dns 10.1.1.1
    set host "www.cbc.com"
    set result [RESOLV::lookup @$dns -a $host]

    log local0. "DNS => $dns | Query A: $host | Result: $result"

    if { $result ne "" } {
        log local0. "Selected Node -> [lindex $result 0]:443"
        node [lindex $result 0] 443
    } else {
        log local0. "No valid IP resolved"
        reject
    }

    unset dns host result
}

Regards.