Hadoop: How to access a HDFS from an external IP? - hadoop

Question

Internally (i.e. internal network; private IP address-to-private IP address), I can access my HDFS just fine using:
hdfs dfs -ls hdfs://#.#.#.#/
However, when I try the same from a machine outside the network on which the HDFS namenode resides (obviously using the namenode machine's WAN IP instead of its LAN IP), I get:
ls: DestHost:destPort ec2-▒-▒-▒-▒.compute-1.amazonaws.com:8020 , LocalHost:localPort mymachine/127.0.0.1:0. Failed on local exception: java.io.IOException: Connection reset by peer
The namenode log reads:
INFO org.apache.hadoop.ipc.Server: Socket Reader #1 for port 8020: readAndProcess from client ▒.▒.▒.▒:▒ threw exception [java.io.IOException: Connection reset by peer]
java.io.IOException: Connection reset by peer
at sun.nio.ch.FileDispatcherImpl.read0(Native Method)
at sun.nio.ch.SocketDispatcher.read(SocketDispatcher.java:39)
at sun.nio.ch.IOUtil.readIntoNativeBuffer(IOUtil.java:223)
at sun.nio.ch.IOUtil.read(IOUtil.java:197)
at sun.nio.ch.SocketChannelImpl.read(SocketChannelImpl.java:377)
at org.apache.hadoop.ipc.Server.channelRead(Server.java:3486)
at org.apache.hadoop.ipc.Server.access$2600(Server.java:138)
at org.apache.hadoop.ipc.Server$Connection.readAndProcess(Server.java:2144)
at org.apache.hadoop.ipc.Server$Listener.doRead(Server.java:1389)
at org.apache.hadoop.ipc.Server$Listener$Reader.doRunLoop(Server.java:1245)
at org.apache.hadoop.ipc.Server$Listener$Reader.run(Server.java:1216)
My core-site.xml reads:
<configuration>
<property>
<name>fs.defaultFS</name>
<value>hdfs://0.0.0.0:8020</value>
</property>
</configuration>
Note that I have also tried setting the fs.defaultFS value to hdfs://#.#.#.#:8020. I have also tried setting it to hdfs://hadoophost:8020, and adding #.#.#.# hadoophost to the top of /etc/hosts. (#.#.#.# is obviously the LAN IP of the namenode's machine in both cases.) The results have been the same.
My hdfs-site.xml reads:
<configuration>
<property>
<name>dfs.replication</name>
<value>1</value>
</property>
<property>
<name>dfs.name.dir</name>
<value>file:///home/hadoop/hadoopdata/hdfs/namenode</value>
</property>
<property>
<name>dfs.data.dir</name>
<value>file:///home/hadoop/hadoopdata/hdfs/datanode</value>
</property>
</configuration>
Note that I am able to telnet externally to the namenode's machine on port 8020 just fine.
What setting(s) am I missing to enable external access to my Hadoop file system?