DNS Forwarders Error

Suddenly internet resolution is failing sparodically. I have conducted a
DCDIAG DNS test a domain controller and here are the results. It states
that the forwarders are unavailable and root hints are also failing. Any
ideas as internet works, goes down for 5min, then comes back up again
throughout the day.

Thanks

Rustom


DC: sfcad03.tsi.internal
Domain: tsi.internal


TEST: Authentication (Auth)
Error: Authentication failed with specified credentials

TEST: Basic (Basc)
Error: No LDAP connectivity
Error: No WMI connectivity


DC: sfcad05.tsi.internal
Domain: tsi.internal


TEST: Forwarders/Root hints (Forw)
Error: Forwarders list has invalid forwarder: 12.127.16.67
(<name unavailable>)
Error: Forwarders list has invalid forwarder: 12.127.17.71
(<name unavailable>)
Error: Forwarders list has invalid forwarder: 199.249.18.1
(<name unavailable>)
Error: Forwarders list has invalid forwarder: 199.249.19.1
(<name unavailable>)
Error: Root hints list has invalid root hint server:
a.root-servers.net. (198.41.0.4)
Error: Root hints list has invalid root hint server:
b.root-servers.net. (192.228.79.201)
Error: Root hints list has invalid root hint server:
c.root-servers.net. (192.33.4.12)
Error: Root hints list has invalid root hint server:
d.root-servers.net. (128.8.10.90)
Error: Root hints list has invalid root hint server:
e.root-servers.net. (192.203.230.10)
Error: Root hints list has invalid root hint server:
f.root-servers.net. (192.5.5.241)
Error: Root hints list has invalid root hint server:
g.root-servers.net. (192.112.36.4)
Error: Root hints list has invalid root hint server:
h.root-servers.net. (128.63.2.53)
Error: Root hints list has invalid root hint server:
i.root-servers.net. (192.36.148.17)
Error: Root hints list has invalid root hint server:
j.root-servers.net. (192.58.128.30)
Error: Root hints list has invalid root hint server:
k.root-servers.net. (193.0.14.129)
Error: Root hints list has invalid root hint server:
l.root-servers.net. (198.32.64.12)
Error: Root hints list has invalid root hint server:
m.root-servers.net. (202.12.27.33)