See e.g.:
https://jenkins.mw.lab.eng.bos.redhat.com/hudson/view/EAP6/view/EAP6-AS-Testsuite/job/eap-60-as-testsuite-RHEL-OracleJDK7-pureIPV6/72/testReport/

Example stacktrace: 
java.lang.RuntimeException: org.eclipse.aether.resolution.ArtifactResolutionException: Could not transfer artifact org.jboss.as:jboss-as-ee:jar:7.1.3.Final-redhat-4 from/to jboss-product-repository (http://download.lab.bos.redhat.com/brewroot/repos/jb-eap-6-rhel-6-build/latest/maven/): Connection to http://download.lab.bos.redhat.com refused
	at org.jboss.as.model.test.MavenUtil.createMavenGavURL(MavenUtil.java:134)
	at org.jboss.as.model.test.ChildFirstClassLoaderBuilder.addMavenResourceURL(ChildFirstClassLoaderBuilder.java:191)
	at org.jboss.as.subsystem.test.SubsystemTestDelegate$LegacyKernelServiceInitializerImpl.addMavenResourceURL(SubsystemTestDelegate.java:698)
	at org.jboss.as.ee.subsystem.EeSubsystemTestCase.testTransformers1_0_0(EeSubsystemTestCase.java:140)
	at org.jboss.as.ee.subsystem.EeSubsystemTestCase.testTransformersEAP601(EeSubsystemTestCase.java:116)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:606)
	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
	at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
	at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:27)
	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
	at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
	at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
	at org.apache.maven.surefire.junit4.JUnit4Provider.execute(JUnit4Provider.java:234)
	at org.apache.maven.surefire.junit4.JUnit4Provider.executeTestSet(JUnit4Provider.java:133)
	at org.apache.maven.surefire.junit4.JUnit4Provider.invoke(JUnit4Provider.java:114)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:606)
	at org.apache.maven.surefire.util.ReflectionUtils.invokeMethodWithArray(ReflectionUtils.java:188)
	at org.apache.maven.surefire.booter.ProviderFactory$ProviderProxy.invoke(ProviderFactory.java:166)
	at org.apache.maven.surefire.booter.ProviderFactory.invokeProvider(ProviderFactory.java:86)
	at org.apache.maven.surefire.booter.ForkedBooter.runSuitesInProcess(ForkedBooter.java:101)
	at org.apache.maven.surefire.booter.ForkedBooter.main(ForkedBooter.java:74)
Caused by: org.eclipse.aether.resolution.ArtifactResolutionException: Could not transfer artifact org.jboss.as:jboss-as-ee:jar:7.1.3.Final-redhat-4 from/to jboss-product-repository (http://download.lab.bos.redhat.com/brewroot/repos/jb-eap-6-rhel-6-build/latest/maven/): Connection to http://download.lab.bos.redhat.com refused
	at org.eclipse.aether.internal.impl.DefaultArtifactResolver.resolve(DefaultArtifactResolver.java:460)
	at org.eclipse.aether.internal.impl.DefaultArtifactResolver.resolveArtifacts(DefaultArtifactResolver.java:262)
	at org.eclipse.aether.internal.impl.DefaultArtifactResolver.resolveArtifact(DefaultArtifactResolver.java:239)
	at org.eclipse.aether.internal.impl.DefaultRepositorySystem.resolveArtifact(DefaultRepositorySystem.java:295)
	at org.jboss.as.model.test.MavenUtil.createMavenGavURL(MavenUtil.java:132)
	... 35 more
Caused by: org.eclipse.aether.transfer.ArtifactTransferException: Could not transfer artifact org.jboss.as:jboss-as-ee:jar:7.1.3.Final-redhat-4 from/to jboss-product-repository (http://download.lab.bos.redhat.com/brewroot/repos/jb-eap-6-rhel-6-build/latest/maven/): Connection to http://download.lab.bos.redhat.com refused
	at org.eclipse.aether.connector.basic.ArtifactTransportListener.transferFailed(ArtifactTransportListener.java:43)
	at org.eclipse.aether.connector.basic.BasicRepositoryConnector$TaskRunner.run(BasicRepositoryConnector.java:342)
	at org.eclipse.aether.util.concurrency.RunnableErrorForwarder$1.run(RunnableErrorForwarder.java:67)
	at org.eclipse.aether.connector.basic.BasicRepositoryConnector$DirectExecutor.execute(BasicRepositoryConnector.java:649)
	at org.eclipse.aether.connector.basic.BasicRepositoryConnector.get(BasicRepositoryConnector.java:247)
	at org.eclipse.aether.internal.impl.DefaultArtifactResolver.performDownloads(DefaultArtifactResolver.java:536)
	at org.eclipse.aether.internal.impl.DefaultArtifactResolver.resolve(DefaultArtifactResolver.java:437)
	... 39 more
Caused by: org.apache.http.conn.HttpHostConnectException: Connection to http://download.lab.bos.redhat.com refused
	at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:190)
	at org.apache.http.impl.conn.ManagedClientConnectionImpl.open(ManagedClientConnectionImpl.java:294)
	at org.apache.http.impl.client.DefaultRequestDirector.tryConnect(DefaultRequestDirector.java:640)
	at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:479)
	at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:906)
	at org.apache.http.impl.client.DecompressingHttpClient.execute(DecompressingHttpClient.java:137)
	at org.eclipse.aether.transport.http.HttpTransporter.execute(HttpTransporter.java:294)
	at org.eclipse.aether.transport.http.HttpTransporter.implGet(HttpTransporter.java:250)
	at org.eclipse.aether.spi.connector.transport.AbstractTransporter.get(AbstractTransporter.java:59)
	at org.eclipse.aether.connector.basic.BasicRepositoryConnector$GetTaskRunner.runTask(BasicRepositoryConnector.java:418)
	at org.eclipse.aether.connector.basic.BasicRepositoryConnector$TaskRunner.run(BasicRepositoryConnector.java:337)
	... 44 more
Caused by: java.net.ConnectException: Network is unreachable
	at java.net.PlainSocketImpl.socketConnect(Native Method)
	at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:339)
	at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:200)
	at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:182)
	at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
	at java.net.Socket.connect(Socket.java:579)
	at org.apache.http.conn.scheme.PlainSocketFactory.connectSocket(PlainSocketFactory.java:127)
	at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:180)
	... 54 more