diff --git a/3.4.6/centos/7/Dockerfile b/3.4.6/centos/7/Dockerfile
index 77281d2..12896af 100644
--- a/3.4.6/centos/7/Dockerfile
+++ b/3.4.6/centos/7/Dockerfile
@@ -4,6 +4,11 @@ RUN yum install -y java-1.7.0-openjdk-headless tar
 
 RUN curl -fL http://mirror.catn.com/pub/apache/zookeeper/stable/zookeeper-3.4.6.tar.gz | tar xzf - -C /opt && mv /opt/zookeeper-3.4.6 /opt/zookeeper
 
+RUN echo "networkaddress.cache.ttl=0" >> /usr/lib/jvm/jre/lib/security/java.security && \
+    sed -i 's/networkaddress.cache.negative.ttl=10/networkaddress.cache.negative.ttl=0/g' /usr/lib/jvm/jre/lib/security/java.security
+
+EXPOSE 2181 2888 3888
+
 VOLUME /tmp/zookeeper
 
 COPY entrypoint.sh /
diff --git a/3.4.6/centos/7/entrypoint.sh b/3.4.6/centos/7/entrypoint.sh
index 3ca7b6a..d49a875 100755
--- a/3.4.6/centos/7/entrypoint.sh
+++ b/3.4.6/centos/7/entrypoint.sh
@@ -1,12 +1,13 @@
-#!/bin/sh
+#!/bin/bash
 
 # based on https://github.com/apache/zookeeper/blob/trunk/conf/zoo_sample.cfg
 cat > /opt/zookeeper/conf/zoo.cfg <<EOF
-tickTime=2000
-initLimit=10
-syncLimit=5
+tickTime=${TICK_TIME:-2000}
+initLimit=${INIT_LIMIT:-10}
+syncLimit=${SYNC_LIMIT:-5}
 dataDir=/tmp/zookeeper
 clientPort=2181
+cnxTimeout=${CNX_TO_MS:-5000}
 EOF
 
 # server.1=...
diff --git a/3.4.6/ubuntu/14.04/Dockerfile b/3.4.6/ubuntu/14.04/Dockerfile
index 9576192..79156c0 100644
--- a/3.4.6/ubuntu/14.04/Dockerfile
+++ b/3.4.6/ubuntu/14.04/Dockerfile
@@ -4,6 +4,11 @@ RUN apt-get update && apt-get install -y curl openjdk-7-jre-headless python
 
 RUN curl -fL http://mirror.catn.com/pub/apache/zookeeper/stable/zookeeper-3.4.6.tar.gz | tar xzf - -C /opt && mv /opt/zookeeper-3.4.6 /opt/zookeeper
 
+RUN echo "networkaddress.cache.ttl=0" >> /etc/java-7-openjdk/security/java.security && \
+    sed -i 's/networkaddress.cache.negative.ttl=10/networkaddress.cache.negative.ttl=0/g' /etc/java-7-openjdk/security/java.security
+
+EXPOSE 2181 2888 3888
+
 VOLUME /tmp/zookeeper
 
 COPY entrypoint.sh /
diff --git a/3.4.6/ubuntu/14.04/entrypoint.sh b/3.4.6/ubuntu/14.04/entrypoint.sh
index 3ca7b6a..d49a875 100755
--- a/3.4.6/ubuntu/14.04/entrypoint.sh
+++ b/3.4.6/ubuntu/14.04/entrypoint.sh
@@ -1,12 +1,13 @@
-#!/bin/sh
+#!/bin/bash
 
 # based on https://github.com/apache/zookeeper/blob/trunk/conf/zoo_sample.cfg
 cat > /opt/zookeeper/conf/zoo.cfg <<EOF
-tickTime=2000
-initLimit=10
-syncLimit=5
+tickTime=${TICK_TIME:-2000}
+initLimit=${INIT_LIMIT:-10}
+syncLimit=${SYNC_LIMIT:-5}
 dataDir=/tmp/zookeeper
 clientPort=2181
+cnxTimeout=${CNX_TO_MS:-5000}
 EOF
 
 # server.1=...