Symptom
reverse DNS lookup queries fail due to corruption when IPv6 DNS PTR queries are being routed through the device running 16.10.1 or later releases.
Client -------- Router (UUT) -------- DNS Server
Packet entering the router is:
0.2.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.5.9.0.0.0.1.7.0.0.8.5.3.0.4.2.ip6.arpa @2404:9400:20f5:9850::21
Packet leaving the router is:
0.0.2.0.0.0.0.0.0.0.0.0.0.0.0.0.0.5.9.0.0.0.1.7.0.0.8.5.3.0.4.2.ip6.arpa
Router in this case is just a transit device.
Conditions
configuration has:
ip nat service dns-v6
It is enabled by default
Workaround
no ip nat service dns-v6 (and disable the dns-v6 NAT ALG)
Downgrade to 16.9.2 or 16.9.3 and there is no such issue.
Further Problem Description
NA
