The test case
api/java_net/InetAddress/complement.html#isReachable
fails on Linux if run on behalf of root but passed if run on behalf of unprivileged user.

Testsuite name: JCK 6b
JDK/JRE tested: 1.6.0_20 b03_jfb
OS/architecture: linux i586
Reproducible: Always
Reproducible on machine: stt-52
Is it a platform specific regression: Y
Is it a new platform support: N
Is it a Regression: N
Test result on FCS: Fail (1.6.0 FCS)
Test run log location: N/A
Steps to reproduce: Just perform class on Linux x86 platfrom with commnd line like below

[root@stt-52 jdk]# /export/jdk/jdk1.6.0_20_b03/bin/java -cp /set/stt/jck_promotions/6b/latest/binaries/JCK-runtime-6b/classes:/export/jdk/jdk1.6.0_19/lib/tools.jar javasoft.sqe.tests.api.java.net.InetAddress.isReachableTests -network.testHost1 spb-void.russia.sun.com/10.16.106.53
isReachable001: Passed. OKAY
isReachable002: Passed. OKAY
isReachable003: Failed. java.net.SocketException: Invalid argument
isReachableIf002: Passed. OKAY
isReachable002: testHost1 spb-void.russia.sun.com/10.16.106.53
java.net.SocketException: Invalid argument
        at java.net.Inet6AddressImpl.isReachable0(Native Method)
        at java.net.Inet6AddressImpl.isReachable(Inet6AddressImpl.java:59)
        at java.net.InetAddress.isReachable(InetAddress.java:420)
        at javasoft.sqe.tests.api.java.net.InetAddress.isReachableTests.isReachable003(isReachableTests.java:144)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:597)
        at javasoft.sqe.javatest.lib.MultiTest.invokeTestCase(MultiTest.java:406)
        at javasoft.sqe.jck.lib.MultiTestExt.invokeTestCase(MultiTestExt.java:55)
        at javasoft.sqe.javatest.lib.MultiTest.run(MultiTest.java:195)
        at javasoft.sqe.javatest.lib.MultiTest.run(MultiTest.java:127)
        at javasoft.sqe.tests.api.java.net.InetAddress.isReachableTests.main(isReachableTests.java:43)
isReachableIf002: netIntf 'name:eth0 (eth0) index: 2 addresses:
/fe80:0:0:0:21b:11ff:feb1:ed6%2;
/fc00:106a:0:0:21b:11ff:feb1:ed6%2;
/10.16.108.151;
', isUp() = true
STATUS:Failed.test cases: 4; passed: 3; failed: 1; first test case failure: isReachable003

Looks like a loopback interface is not valid for java.net.InetAddress.isReachable() method if it run on behalf of root user. At least if the line 144 in the test case rewrite with
            if( ia1.isReachable(null, ttl, HUGE_TIMEOUT ) )
the host will be reachable. Moreover if the first argument of the method is non loopback interface the Exception will not occur. The exception exists only if the NetworkInterface is loop back interface. Why loopback interface is invalid argument if test started on behalf of root user? ... and valid if it started on behalf of unprivileged user?

Actually the test isReachable003() is strange. The comment to the method is not correct by my opinion. The test will be passed if the Host will be not reachable (in the comment another description).

Any way the test passed if it run on behalf of the user without root privileges:
[stt-robot@stt-52]$ /export/jdk/jdk1.6.0_20_b03/bin/java -cp /set/stt/jck_promotions/6b/latest/binaries/JCK-runtime-6b/classes:/export/jdk/jdk1.6.0_19/lib/tools.jar javasoft.sqe.tests.api.java.net.InetAddress.isReachableTests -network.testHost1 spb-void.russia.sun.com/10.16.106.53
isReachable001: Passed. OKAY
isReachable002: Passed. OKAY
isReachable003: Passed. OK
isReachableIf002: Passed. OKAY
isReachable002: testHost1 spb-void.russia.sun.com/10.16.106.53
isReachableIf002: netIntf 'name:eth0 (eth0) index: 2 addresses:
/fe80:0:0:0:21b:11ff:feb1:ed6%2;
/fc00:106a:0:0:21b:11ff:feb1:ed6%2;
/10.16.108.151;
', isUp() = true
STATUS:Passed.test cases: 4; all passed

It is Linux specific issue. On Solaris the test passes with root privileges. But! it spend extremely more time with root than with unprivileged user.
Test name:
api/java_net/InetAddress/complement_isReachable