android/guava/src/com/google/common/net/InetAddresses.java
public static boolean isTeredoAddress(Inet6Address ip) {
    byte[] bytes = ip.getAddress();
    return (bytes[0] == (byte) 0x20)
        && (bytes[1] == (byte) 0x01)
        && (bytes[2] == 0)
        && (bytes[3] == 0);
  }
public static boolean isTeredoAddress(Inet6Address ip) {
    byte[] bytes = ip.getAddress();
    return (bytes[0] == (byte) 0x20)
        && (bytes[1] == (byte) 0x01)
        && (bytes[2] == 0)
        && (bytes[3] == 0);
  }
Evaluates whether the argument is a Teredo address.

<p>Teredo addresses begin with the {@code "2001::/32"} prefix.

@param ip {@link Inet6Address} to be examined for Teredo address format
@return {@code true} if the argument is a Teredo address