Instances do not get ip address from dhcp agent in Openstack.

Issue

• We created the net,subnet and router without any issue but when we are deploying a VM the network doesnt work, the VM doesnt have any ip address and ports are down, we configured Neutron with openvswitch. How can we troubleshoot this issue?

• Dhcp agent fails to bring up dnsmasq process required to allocate dhcp ip to instances with below error.

Command: ['sudo', 'quantum-rootwrap', '/etc/quantum/rootwrap.conf', 'QUANTUM_RELAY_SOCKET_PATH=/var/lib/quantum/dhcp/lease_relay', 'QUANTUM_NETWORK_ID=629b834a-8f38-4d73-ab34-194bf859ebfd', 'dnsmasq', '--no-hosts', '--no-resolv', '--strict-order', '--bind-interfaces', '--interface=ns-71957019-ad', '--except-interface=lo', '--pid-file=/var/lib/quantum/dhcp/629b834a-8f38-4d73-ab34-194bf859ebfd/pid', '--dhcp-hostsfile=/var/lib/quantum/dhcp/629b834a-8f38-4d73-ab34-194bf859ebfd/host', '--dhcp-optsfile=/var/lib/quantum/dhcp/629b834a-8f38-4d73-ab34-194bf859ebfd/opts', '--dhcp-script=/usr/bin/quantum-dhcp-agent-dnsmasq-lease-update', '--leasefile-ro', '--dhcp-range=tag0,172.16.16.0,static,120s', '--conf-file=', '--domain=openstacklocal']
Exit code: 2
Stdout: ''
Stderr: '\ndnsmasq: failed to bind listening socket for fe80::f816:3eff:fe34:42f4: Address already in use\n'
2013-08-19 10:06:07     INFO [quantum.agent.dhcp_agent] Synchronizing state
2013-08-19 10:06:07    ERROR [quantum.agent.dhcp_agent] Unable to enable dhcp.
Traceback (most recent call last):
  File "/usr/lib/python2.6/site-packages/quantum/agent/dhcp_agent.py", line 131, in call_driver
    getattr(driver, action)()
  File "/usr/lib/python2.6/site-packages/quantum/agent/linux/dhcp.py", line 129, in enable
    self.spawn_process()
  File "/usr/lib/python2.6/site-packages/quantum/agent/linux/dhcp.py", line 329, in spawn_process
    utils.execute(cmd, self.root_helper)
  File "/usr/lib/python2.6/site-packages/quantum/agent/linux/utils.py", line 61, in execute
    raise RuntimeError(m)
RuntimeError:
Command: ['sudo', 'quantum-rootwrap', '/etc/quantum/rootwrap.conf', 'QUANTUM_RELAY_SOCKET_PATH=/var/lib/quantum/dhcp/lease_relay', 'QUANTUM_NETWORK_ID=629b834a-8f38-4d73-ab34-194bf859ebfd', 'dnsmasq', '--no-hosts', '--no-resolv', '--strict-order', '--bind-interfaces', '--interface=ns-71957019-ad', '--except-interface=lo', '--pid-file=/var/lib/quantum/dhcp/629b834a-8f38-4d73-ab34-194bf859ebfd/pid', '--dhcp-hostsfile=/var/lib/quantum/dhcp/629b834a-8f38-4d73-ab34-194bf859ebfd/host', '--dhcp-optsfile=/var/lib/quantum/dhcp/629b834a-8f38-4d73-ab34-194bf859ebfd/opts', '--dhcp-script=/usr/bin/quantum-dhcp-agent-dnsmasq-lease-update', '--leasefile-ro', '--dhcp-range=tag0,172.16.16.0,static,120s', '--conf-file=', '--domain=openstacklocal']
Exit code: 2
Stdout: ''
Stderr: '\ndnsmasq: failed to bind listening socket for fe80::f816:3eff:fe34:42f4: Address already in use\n'