Internet access and R CMD make check-devel

I am trying to install R on CentOS (either 7 or 8, behavior is the
same) in an environment behind a firewall and while I am able to run:

R CMD make check

I am unable to run:

R CMD make check-devel

These latter tests fail. The failure occurs in the internet access
if() conditional statement in these two tests:

https://svn.r-project.org/R/trunk/tests/internet.R
https://svn.r-project.org/R/trunk/tests/internet2.R

In my environment, nsl("cran.r-project.org") returns a valid, non-null
value but subsequent commands in those test files do not successfully
access the internet.

I'd like to be able to run the full test suite given I am building
from source. I'm wondering if it's possible to make these conditionals
more strict so that the conditional tests internet access in a manner
more similar to how internet access is used in the tests. Would this
be possible? Or, make tests that require internet access into a
distinct `check-internet` or similar?

As an additional reference, the same conditional statement appears to
also be used in these other tests:

https://svn.r-project.org/R/trunk/tests/CRANtools.R
https://svn.r-project.org/R/trunk/tests/libcurl.R

Thanks,
-Thomas

Thomas J. Leeper