A question about proxying Jenkins maven repo

[Eric Griswold]

Hello,

I'm running the FOSS version of Nexus Repository Manager, 2.12.0-01

For a time, our proxy of
http://maven.jenkins-ci.org/content/repositories/releases/ was working
well but I've noticed it going out of service (for how long I cannot way).

Even after following the guide in
https://wiki.jenkins-ci.org/display/JENKINS/Jenkins+Development+Environment+with+Nexus,

I'm not finding, for example, >2.x jenkins-core artifacts and I see an
error with my proxy discovery:

Status:Unsuccessful.
Message: Connect to maven.jenkins-ci.org:80
[maven.jenkins-ci.org/199.193.196.24] failed: Connection timed out

Are there any hints/docs to help get this back running?

Thanks
Eric Griswold