Can't ping or ssh an instance on anything but control node

I have been trying to set up a multi-node OpenStack cloud network for some time now, and I keep hitting this one stumbling block.

I get the control node up, running all the OpenStack services, and I can deploy an instance and ssh into it. If I add a compute node, an instance that gets created there I can't ssh or ping.

I've included the two nova.conf files, along with the interfaces files. Please help, this is driving me insane.

To keep it simple, here's a description of a base configuration that exhibits this:

Control node - two nics (eth0 and eth1) running keystone/glance/nova-*/mysql

Compute node - two nics (eth0 and eth1) running nova-compute, nova-network, mysql-client, postresql-client

eth0 is on a public LAN, with a fixed address in both cases (192.168.1.14 and 192.168.1.15)

eth1 is connected to a private ethernet switch (Cisco)

--------------
Controller
--------------
nova.conf
--------------

--dhcpbridge=/usr/bin/nova-dhcpbridge
--logdir=/var/log/nova
--state_path=/var/lib/nova
--lock_path=/var/lock/nova
--allow_admin_api=true
--use_deprecated_auth=false
--auth_strategy=keystone
--scheduler_driver=nova.scheduler.simple.SimpleScheduler
--s3_host=192.168.1.14
--ec2_host=192.168.1.14
--rabbit_host=192.168.1.14
--cc_host=192.168.1.14
--nova_url=http://192.168.1.14:8774/v1.1/
--routing_source_ip=192.168.1.14
--glance_api_servers=192.168.1.14:9292
--image_service=nova.image.glance.GlanceImageService
--iscsi_ip_prefix=172.31.252
--sql_connection=mysql://nova:openstack@192.168.1.14/nova
--ec2_url=http://192.168.1.14:8773/services/Cloud
--keystone_ec2_url=http://192.168.1.14:5000/v2.0/ec2tokens
--api_paste_config=/etc/nova/api-paste.ini
--libvirt_type=kvm
--libvirt_use_virtio_for_bridges=true
--start_guests_on_host_boot=true
--resume_guests_state_on_host_boot=true
--vnc_enabled=true
--vncproxy_url=http:/192.168.1.14:6080
--vnc_console_proxy_url=http://192.168.1.14:6080
##### network specific settings #####
--network_manager=nova.network.manager.FlatDHCPManager
--public_interface=eth0
--flat_interface=eth1
--flat_network_bridge=br100
--fixed_range=172.31.252.32/23
#--floating_range=128.163.188.240/27
#--auto_assign_floating_ip=True
--network_size=500
--flat_network_dhcp_start=172.31.252.10
--flat_injected=False
--force_dhcp_release
--iscsi_helper=tgtadm
--connection_type=libvirt
--root_helper=sudo nova-rootwrap
--verbose
--max_cores=250

----------------------------------
/etc/network/interfaces
----------------------------------
# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
auto eth0
iface eth0 inet static
    address 192.168.1.14
    netmask 255.255.255.0
    broadcast 192.168.1.255
    network 192.168.1.0
    gateway 192.168.1.1
    dns-nameservers 192.168.1.1

auto br100
iface br100 inet static
    bridge_ports eth1
    bridge_stp off
    bridge_maxwait 0
    bridge_fd 0
    address 172.31.252.1
    netmask 255.255.254.0

---------------------
Compute Node
---------------------
nova.conf
--------------
--dhcpbridge=/usr/bin/nova-dhcpbridge
--logdir=/var/log/nova
--state_path=/var/lib/nova
--lock_path=/var/lock/nova
--allow_admin_api=true
--use_deprecated_auth=false
--auth_strategy=keystone
--scheduler_driver=nova.scheduler.simple.SimpleScheduler
--s3_host=192.168.1.14
--ec2_host=192.168.1.14
--rabbit_host=192.168.1.14
--cc_host=192.168.1.14
--nova_url=http://192.168.1.14:8774/v1.1/
--routing_source_ip=192.168.1.14
--glance_api_servers=192.168.1.14:9292
--image_service=nova.image.glance.GlanceImageService
--iscsi_ip_prefix=172.31.252
--sql_connection=mysql://nova:openstack@192.168.1.14/nova
--ec2_url=http://192.168.1.14:8773/services/Cloud
--keystone_ec2_url=http://192.168.1.14:5000/v2.0/ec2tokens
--api_paste_config=/etc/nova/api-paste.ini
--libvirt_type=kvm
--libvirt_use_virtio_for_bridges=true
--start_guests_on_host_boot=true
--resume_guests_state_on_host_boot=true
--vnc_enabled=true
--vncproxy_url=http:/192.168.1.14:6080
--vnc_console_proxy_url=http://192.168.1.14:6080
##### network specific settings #####
--network_manager=nova.network.manager.FlatDHCPManager
--public_interface=eth0
--flat_interface=eth1
--flat_network_bridge=br100
--fixed_range=172.31.252.32/23
#--floating_range=128.163.188.240/27
#--auto_assign_floating_ip=True
--network_size=500
--flat_network_dhcp_start=172.31.252.10
--flat_injected=False
--force_dhcp_release
--iscsi_helper=tgtadm
--connection_type=libvirt
--root_helper=sudo nova-rootwrap
--verbose
--max_cores=250

----------------------------------
/etc/network/interfaces
----------------------------------
# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
auto eth0
iface eth0 inet static
    address 192.168.1.15
    netmask 255.255.255.0
    broadcast 192.168.1.255
    network 192.168.1.0
    gateway 192.168.1.1
    dns-nameservers 192.168.1.1

auto br100
iface br100 inet static
    bridge_ports eth1
    bridge_stp off
    bridge_maxwait 0
    bridge_fd 0
    address 172.31.252.2
    netmask 255.255.254.0