diff --git a/bin/make-base-vm b/bin/make-base-vm
index ceedc43..c1920f3 100755
--- a/bin/make-base-vm
+++ b/bin/make-base-vm
@@ -20,10 +20,10 @@ usage() {
   --vbox     use VirtualBox instead of kvm
 
   The MIRROR_HOST environment variable can be used to change the
-  apt-cacher host.  It should be something that the target VM can
-  resolve.  It may be set to 127.0.0.1, in which case it will be
-  changed to 10.0.2.2 on the guest.  10.0.2.2 is the host IP as visible
-  from the guest under qemu networking.
+  apt-cacher host.  It should be something that both the host and the
+  target VM can reach.  It may be set to 127.0.0.1, in which case it will be
+  changed to 10.0.2.2 on the guest (or GITIAN_HOST_IP if it is defined)
+  10.0.2.2 is the host IP as visible from the guest under qemu networking.
 EOF
 }
 
@@ -104,6 +104,7 @@ if [ -e $OUT.qcow2 ]; then
   exit 1
 fi
 
+libexec/config-bootstrap-fixup
 rm -rf $OUT
 sudo vmbuilder kvm ubuntu --rootsize 10240 --arch=$ARCH --suite=$SUITE --addpkg=$addpkg --removepkg=$removepkg --ssh-key=var/id_dsa.pub --ssh-user-key=var/id_dsa.pub --mirror=$MIRROR --security-mirror=$SECURITY_MIRROR --dest=$OUT --flavour=$FLAVOUR --firstboot=`pwd`/target-bin/bootstrap-fixup
 mv $OUT/*.qcow2 $OUT.qcow2
diff --git a/etc/lxc.config.in b/etc/lxc.config.in
index b4c02e5..5397170 100644
--- a/etc/lxc.config.in
+++ b/etc/lxc.config.in
@@ -26,7 +26,9 @@ lxc.mount.entry=sysfs ROOTFS/sys sysfs defaults  0 0
 # Container with network virtualized using a pre-configured bridge named br0 and
 # veth pair virtual network devices
 # On the host, run: ifconfig br0 up 10.0.2.2
+# Alternatively, you can use another IP range for the bridge interface, in this case set
+# the environment variables GITIAN_HOST_IP and LXC_GUEST_IP appropriately.
 lxc.network.type = veth
 lxc.network.flags = up
 lxc.network.link = br0
-lxc.network.ipv4 = 10.0.2.5/24
+lxc.network.ipv4 = GUESTIP/24
diff --git a/libexec/config-bootstrap-fixup b/libexec/config-bootstrap-fixup
new file mode 100755
index 0000000..61d69b0
--- /dev/null
+++ b/libexec/config-bootstrap-fixup
@@ -0,0 +1,15 @@
+#!/bin/bash
+
+wd=`pwd`
+
+# Default host IP is 10.0.2.2
+if [ -z "$GITIAN_HOST_IP" ]; then
+  GITIAN_HOST_IP=10.0.2.2
+fi
+
+# Default to host IP if the MIRROR_HOST is not set, or set to 127.0.0.1
+if [ -z "$MIRROR_HOST" ] || [ "$MIRROR_HOST" == "127.0.0.1" ]; then
+  MIRROR_HOST=$GITIAN_HOST_IP
+fi
+
+sed "s;HOSTIP;$MIRROR_HOST;g" < target-bin/bootstrap-fixup.in > target-bin/bootstrap-fixup
diff --git a/libexec/config-lxc b/libexec/config-lxc
index bc401af..fa6cac0 100755
--- a/libexec/config-lxc
+++ b/libexec/config-lxc
@@ -1,4 +1,9 @@
 #!/bin/bash
 
 wd=`pwd`
-sed "s;ROOTFS;$wd/target-$LXC_SUITE-$LXC_ARCH;;s;ARCH;$LXC_ARCH;g" < etc/lxc.config.in > var/lxc.config
+
+if [ -z "$LXC_GUEST_IP" ]; then
+    LXC_GUEST_IP=10.0.2.5
+fi
+
+sed "s;ROOTFS;$wd/target-$LXC_SUITE-$LXC_ARCH;;s;ARCH;$LXC_ARCH;g;;s;GUESTIP;$LXC_GUEST_IP;g" < etc/lxc.config.in > var/lxc.config
diff --git a/libexec/make-clean-vm b/libexec/make-clean-vm
index e6400c1..68b7b8a 100755
--- a/libexec/make-clean-vm
+++ b/libexec/make-clean-vm
@@ -60,6 +60,7 @@ case $VMSW in
     ;;
   LXC)
     cp -a $BASE $OUT
+    libexec/config-bootstrap-fixup
     on-target -u root bash < target-bin/bootstrap-fixup
     ;;
   VBOX)
diff --git a/target-bin/bootstrap-fixup b/target-bin/bootstrap-fixup
deleted file mode 100755
index 6662f31..0000000
--- a/target-bin/bootstrap-fixup
+++ /dev/null
@@ -1,8 +0,0 @@
-#!/bin/sh
-
-set -e
-
-. /etc/lsb-release
-
-echo "deb http://10.0.2.2:3142/archive.ubuntu.com/ubuntu $DISTRIB_CODENAME main universe" > $1/etc/apt/sources.list
-echo "deb http://10.0.2.2:3142/archive.ubuntu.com/ubuntu $DISTRIB_CODENAME-updates main universe" >> $1/etc/apt/sources.list
diff --git a/target-bin/bootstrap-fixup.in b/target-bin/bootstrap-fixup.in
new file mode 100755
index 0000000..1908417
--- /dev/null
+++ b/target-bin/bootstrap-fixup.in
@@ -0,0 +1,8 @@
+#!/bin/sh
+
+set -e
+
+. /etc/lsb-release
+
+echo "deb http://HOSTIP:3142/archive.ubuntu.com/ubuntu $DISTRIB_CODENAME main universe" > $1/etc/apt/sources.list
+echo "deb http://HOSTIP:3142/archive.ubuntu.com/ubuntu $DISTRIB_CODENAME-updates main universe" >> $1/etc/apt/sources.list