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jayanthi_41101's avatar
jayanthi_41101
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8 years ago

Use DNS server list for DNS resolution through F5 LTM irule

We already use DNS resolution using one specific DNS server in RESOLV::lookup. I am trying to figure out a solution where i can use a list of DNS servers and not finding any resources for it.   C...
application delivery
LTM
tcastaing_23984's avatar
tcastaing_23984
Icon for Nimbostratus rankNimbostratus
8 years ago

Here is a working solution that is choosing randomly a DNS server from the specified list.

 FQDN to resolve
set FQDN_TO_RESOLVE "www.example.com"

 DNS server list
set DNS_SERVER_LIST {1.1.1.1 2.2.2.2 3.3.3.3}

 Select a DNS server from the list
set SELECTED_DNS_SERVER "[lindex $DNS_SERVER_LIST [expr {int(rand()*[llength $DNS_SERVER_LIST])}]]"

 Perform the Lookup
set FQDN_RESOLVED_IP "[lindex [RESOLV::lookup @$SELECTED_DNS_SERVER -a $FQDN_TO_RESOLVE] 0]"