eth0.portal-web002.zrh1.exoscale.net has no NS records.
NS records for this zone are defined at exoscale.net.
NS records for this zone are defined at exoscale.net.
Question and response
Question
dig eth0.portal-web002.zrh1.exoscale.net. NS
Answer
The response has no answer records.
Authority
exoscale.net. 300 SOA ns2.exoscale.net. hostmaster.exoscale.net. 1434890148 7200 1800 2419200 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0