[Openstack] Neutron dhcp issues

Abhishek Chanda abhishek.lists at gmail.com
Thu Feb 26 20:17:58 UTC 2015

Hi all,

I am trying to run Juno Neutron in two boxes. One box runs the API
endpoints, the other one runs nova compute and neutron OVS agent.
After I boot up VMs, they do not get a reply for DHCP discover. I
noticed that the broadcasts reach br-int but are getting dropped after
that. Here is my setup:

mngmt3:/opt/openstack # ovs-vsctl show
    Bridge br-tun
        Port br-tun
            Interface br-tun
                type: internal
        Port patch-int
            Interface patch-int
                type: patch
                options: {peer=patch-tun}
        Port "vxlan-ac1a400c"
            Interface "vxlan-ac1a400c"
                type: vxlan
                options: {df_default="true", in_key=flow,
local_ip="", out_key=flow, remote_ip=""}
    Bridge br-int
        fail_mode: secure
        Port int-br-ex
            Interface int-br-ex
                type: patch
                options: {peer=phy-br-ex}
        Port "qvo020cae33-fb"
            Interface "qvo020cae33-fb"
        Port br-int
            Interface br-int
                type: internal
        Port patch-tun
            Interface patch-tun
                type: patch
                options: {peer=patch-int}
    Bridge br-ex
        Port phy-br-ex
            Interface phy-br-ex
                type: patch
                options: {peer=int-br-ex}
        Port br-ex
            Interface br-ex
                type: internal
        Port "eth0"
            Interface "eth0"
    ovs_version: "2.1.3"

mngmt3:/opt/openstack # brctl show
bridge name            bridge id                       STP enabled
docker0                   8000.56847afe9799      no
qbr020cae33-fb        8000.bea5fc15ea51     no


mngmt3:/opt/openstack # ovs-ofctl dump-flows br-int
NXST_FLOW reply (xid=0x4):
 cookie=0x0, duration=245697.535s, table=0, n_packets=25253,
n_bytes=8125454, idle_age=10, hard_age=65534, priority=1
 cookie=0x0, duration=245696.905s, table=0, n_packets=59,
n_bytes=3540, idle_age=1680, hard_age=65534, priority=2,in_port=1
 cookie=0x0, duration=245697.516s, table=23, n_packets=0, n_bytes=0,
idle_age=65534, hard_age=65534, priority=0 actions=drop

mngmt3:/opt/openstack # ovs-ofctl dump-flows br-tun
NXST_FLOW reply (xid=0x4):
 cookie=0x0, duration=245702.144s, table=0, n_packets=2, n_bytes=180,
idle_age=65534, hard_age=65534, priority=0 actions=drop
 cookie=0x0, duration=245702.152s, table=0, n_packets=25251,
n_bytes=8125274, idle_age=15, hard_age=65534, priority=1,in_port=1
 cookie=0x0, duration=245701.592s, table=0, n_packets=1, n_bytes=90,
idle_age=65534, hard_age=65534, priority=1,in_port=2
 cookie=0x0, duration=245702.127s, table=2, n_packets=25251,
n_bytes=8125274, idle_age=15, hard_age=65534,
 cookie=0x0, duration=245702.136s, table=2, n_packets=0, n_bytes=0,
idle_age=65534, hard_age=65534,
 cookie=0x0, duration=245702.118s, table=3, n_packets=0, n_bytes=0,
idle_age=65534, hard_age=65534, priority=0 actions=drop
 cookie=0x0, duration=245702.110s, table=4, n_packets=1, n_bytes=90,
idle_age=65534, hard_age=65534, priority=0 actions=drop
 cookie=0x0, duration=245702.101s, table=10, n_packets=0, n_bytes=0,
idle_age=65534, hard_age=65534, priority=1
 cookie=0x0, duration=245702.093s, table=20, n_packets=0, n_bytes=0,
idle_age=65534, hard_age=65534, priority=0 actions=resubmit(,22)
 cookie=0x0, duration=245702.084s, table=22, n_packets=25251,
n_bytes=8125274, idle_age=15, hard_age=65534, priority=0 actions=drop

Here is what I see:
1. tcpdump on tap020cae33-fb, which is the VM's interface on the host,
shows outgoing DHCP broadcasts.
2. Those also show up in qbr020cae33-fb, qvb020cae33-fb and br-int
3. No traffic shows up in br-tun

Since br-int and br-tun are connected via a patch port, shouldn't they
get identical traffic? How do I debug this?


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