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Unable to Resolve .mil from some subnets


From: Alex Buie via NANOG <nanog () lists nanog org>
Date: Tue, 10 Mar 2026 15:02:06 -0400

Facing an interesting problem with .mil and wondering if anyone has
experienced this or has any ideas.

The .mil nameservers appear to be unresponsive to requests from some of our
subnets (AS396163) starting in the last day or two.

Specifically seems to be these:

mil.                        172800        IN        NS        con1.nipr.mil.
mil.                        172800        IN        NS        con2.nipr.mil.
mil.                        172800        IN        NS        eur1.nipr.mil.
mil.                        172800        IN        NS        eur2.nipr.mil.
mil.                        172800        IN        NS        pac1.nipr.mil.
mil.                        172800        IN        NS        pac2.nipr.mil.

199.252.157.234 / 199.252.162.234 / 199.252.154.234 / 199.252.143.234 /
199.252.180.234 / 199.252.155.234


Subnets that are able to reach / query these servers:
104.234.21.0/24
104.234.31.0/24

Subnets that are not able to query these servers:
166.0.64.0/24
166.0.65.0/24
166.0.66.0/24
166.0.67.0/24

These subnets are announced out of the same carrier mix (Zayo/Cogent/Lumen)
but are geographically distributed around the US. I have checked an RPKI
validator to see if there was a difference between the working and
non-working ones, but all are showing RPKI valid. Path-wise we either take
Zayo which hands off to Lumen or we take Lumen directly, but that does not
seem to have an affect on the queries returning.

I did notice that the working ones have an ISPSS Level3 hop at the end of
the chain, whereas the non-working ones have a hop into an edge for
lumen.tech but no further responses.

Curious if anyone else has found a change or difficulty reaching these
hosts or are seeing DNS resolution issues for .mil TLD domains. Also open
to troubleshooting ideas for further isolating the cause.

Thanks!

Alex
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