Understanding the networking configuration options helps you design the best configuration for your Compute instances.
You can choose to either install and configure nova-network
or use the
OpenStack Networking service (neutron). This section contains a brief
overview of nova-network
. For more information about OpenStack
Networking, see Networking.
Note
nova-network
was deprecated in the OpenStack Newton release.
In Ocata and future releases, you can start nova-network
only with
a cells v1 configuration. This is not a recommended configuration for
deployment.
Compute assigns a private IP address to each VM instance. Compute makes a distinction between fixed IPs and floating IP. Fixed IPs are IP addresses that are assigned to an instance on creation and stay the same until the instance is explicitly terminated. Floating IPs are addresses that can be dynamically associated with an instance. A floating IP address can be disassociated and associated with another instance at any time. A user can reserve a floating IP for their project.
Note
Currently, Compute with nova-network
only supports Linux bridge
networking that allows virtual interfaces to connect to the outside
network through the physical interface.
The network controller with nova-network
provides virtual networks to
enable compute servers to interact with each other and with the public
network. Compute with nova-network
supports the following network modes,
which are implemented as Network Manager types:
br100
,
although this is configurable) on the systems running the
nova-network
service. All instances of the system are attached to
the same bridge, which is configured manually by the network
administrator.Note
Configuration injection currently only works on Linux-style
systems that keep networking configuration in
/etc/network/interfaces
.
In this mode, OpenStack starts a DHCP server (dnsmasq) to allocate IP addresses to VM instances from the specified subnet, in addition to manually configuring the networking bridge. IP addresses for VM instances are assigned from a subnet specified by the network administrator.
Like flat mode, all instances are attached to a single bridge on the
compute node. Additionally, a DHCP server configures instances
depending on single-/multi-host mode, alongside each nova-network
.
In this mode, Compute does a bit more configuration. It attempts to
bridge into an Ethernet device (flat_interface
, eth0 by
default). For every instance, Compute allocates a fixed IP address
and configures dnsmasq with the MAC ID and IP address for the VM.
Dnsmasq does not take part in the IP address allocation process, it
only hands out IPs according to the mapping done by Compute.
Instances receive their fixed IPs with the dhcpdiscover command.
These IPs are not assigned to any of the host’s network interfaces,
only to the guest-side interface for the VM.
In any setup with flat networking, the hosts providing the
nova-network
service are responsible for forwarding traffic from the
private network. They also run and configure dnsmasq as a DHCP
server listening on this bridge, usually on IP address 10.0.0.1 (see
DHCP server: dnsmasq). Compute can determine
the NAT entries for each network, although sometimes NAT is not
used, such as when the network has been configured with all public
IPs, or if a hardware router is used (which is a high availability
option). In this case, hosts need to have br100
configured and
physically connected to any other nodes that are hosting VMs. You
must set the flat_network_bridge
option or create networks with
the bridge parameter in order to avoid raising an error. Compute
nodes have iptables or ebtables entries created for each project and
instance to protect against MAC ID or IP address spoofing and ARP
poisoning.
Note
In single-host Flat DHCP mode you will be able to ping VMs
through their fixed IP from the nova-network
node, but you
cannot ping them from the compute nodes. This is expected
behavior.
This is the default mode for OpenStack Compute. In this mode,
Compute creates a VLAN and bridge for each project. For
multiple-machine installations, the VLAN Network Mode requires a
switch that supports VLAN tagging (IEEE 802.1Q). The project gets a
range of private IPs that are only accessible from inside the VLAN.
In order for a user to access the instances in their project, a
special VPN instance (code named cloudpipe
) needs to be created.
Compute generates a certificate and key for the user to access the
VPN and starts the VPN automatically. It provides a private network
segment for each project’s instances that can be accessed through a
dedicated VPN connection from the internet. In this mode, each
project gets its own VLAN, Linux networking bridge, and subnet.
The subnets are specified by the network administrator, and are assigned dynamically to a project when required. A DHCP server is started for each VLAN to pass out IP addresses to VM instances from the subnet assigned to the project. All instances belonging to one project are bridged into the same VLAN for that project. OpenStack Compute creates the Linux networking bridges and VLANs when required.
These network managers can co-exist in a cloud system. However, because you cannot select the type of network for a given project, you cannot configure multiple network types in a single Compute installation.
All network managers configure the network using network drivers. For
example, the Linux L3 driver (l3.py
and linux_net.py
), which
makes use of iptables
, route
and other network management
facilities, and the libvirt network filtering
facilities. The driver is
not tied to any particular network manager; all network managers use the
same driver. The driver usually initializes only when the first VM lands
on this host node.
All network managers operate in either single-host or multi-host mode.
This choice greatly influences the network configuration. In single-host
mode, a single nova-network
service provides a default gateway for VMs
and hosts a single DHCP server (dnsmasq). In multi-host mode, each
compute node runs its own nova-network
service. In both cases, all
traffic between VMs and the internet flows through nova-network
. Each
mode has benefits and drawbacks. For more on this, see the Network
Topology section in the OpenStack Operations Guide.
All networking options require network connectivity to be already set up
between OpenStack physical nodes. OpenStack does not configure any
physical network interfaces. All network managers automatically create
VM virtual interfaces. Some network managers can also create network
bridges such as br100
.
The internal network interface is used for communication with VMs. The
interface should not have an IP address attached to it before OpenStack
installation, it serves only as a fabric where the actual endpoints are
VMs and dnsmasq. Additionally, the internal network interface must be in
promiscuous
mode, so that it can receive packets whose target MAC
address is the guest VM, not the host.
All machines must have a public and internal network interface
(controlled by these options: public_interface
for the public
interface, and flat_interface
and vlan_interface
for the
internal interface with flat or VLAN managers). This guide refers to the
public network as the external network and the private network as the
internal or project network.
For flat and flat DHCP modes, use the nova network-create command to create a network:
$ nova network-create vmnet \
--fixed-range-v4 10.0.0.0/16 --fixed-cidr 10.0.20.0/24 --bridge br100
This example uses the following parameters:
--fixed-range-v4
--fixed-cidr
--fixed-range-v4
argument.--bridge
The Compute service uses
dnsmasq as the DHCP
server when using either Flat DHCP Network Manager or VLAN Network
Manager. For Compute to operate in IPv4/IPv6 dual-stack mode, use at
least dnsmasq v2.63. The nova-network
service is responsible for
starting dnsmasq processes.
The behavior of dnsmasq can be customized by creating a dnsmasq
configuration file. Specify the configuration file using the
dnsmasq_config_file
configuration option:
dnsmasq_config_file=/etc/dnsmasq-nova.conf
For more information about creating a dnsmasq configuration file, see the OpenStack Configuration Reference, and the dnsmasq documentation.
Dnsmasq also acts as a caching DNS server for instances. You can specify
the DNS server that dnsmasq uses by setting the dns_server
configuration option in /etc/nova/nova.conf
. This example configures
dnsmasq to use Google’s public DNS server:
dns_server=8.8.8.8
Dnsmasq logs to syslog (typically /var/log/syslog
or
/var/log/messages
, depending on Linux distribution). Logs can be
useful for troubleshooting, especially in a situation where VM instances
boot successfully but are not reachable over the network.
Administrators can specify the starting point IP address to reserve with the DHCP server (in the format n.n.n.n) with this command:
$ nova-manage fixed reserve --address IP_ADDRESS
This reservation only affects which IP address the VMs start at, not the
fixed IP addresses that nova-network
places on the bridges.
If you are using OpenStack Compute with nova-network
, you can put
Compute into dual-stack mode, so that it uses both IPv4 and IPv6
addresses for communication. In dual-stack mode, instances can acquire
their IPv6 global unicast addresses by using a stateless address
auto-configuration mechanism [RFC 4862/2462]. IPv4/IPv6 dual-stack mode
works with both VlanManager
and FlatDHCPManager
networking
modes.
In VlanManager
networking mode, each project uses a different 64-bit
global routing prefix. In FlatDHCPManager
mode, all instances use
one 64-bit global routing prefix.
This configuration was tested with virtual machine images that have an
IPv6 stateless address auto-configuration capability. This capability is
required for any VM to run with an IPv6 address. You must use an EUI-64
address for stateless address auto-configuration. Each node that
executes a nova-*
service must have python-netaddr
and radvd
installed.
Switch into IPv4/IPv6 dual-stack mode
For every node running a nova-*
service, install python-netaddr:
# apt-get install python-netaddr
For every node running nova-network
, install radvd
and configure
IPv6 networking:
# apt-get install radvd
# echo 1 > /proc/sys/net/ipv6/conf/all/forwarding
# echo 0 > /proc/sys/net/ipv6/conf/all/accept_ra
On all nodes, edit the nova.conf
file and specify
use_ipv6 = True
.
Restart all nova-*
services.
IPv6 configuration options
You can use the following options with the nova network-create command:
Add a fixed range for IPv6 addresses to the nova network-create
command. Specify public
or private
after the network-create
parameter.
$ nova network-create public --fixed-range-v4 FIXED_RANGE_V4 \
--vlan VLAN_ID --vpn VPN_START --fixed-range-v6 FIXED_RANGE_V6
Set the IPv6 global routing prefix by using the
--fixed_range_v6
parameter. The default value for the parameter
is fd00::/48
.
When you use FlatDHCPManager
, the command uses the original
--fixed_range_v6
value. For example:
$ nova network-create public --fixed-range-v4 10.0.2.0/24 \
--fixed-range-v6 fd00:1::/48
When you use VlanManager
, the command increments the subnet ID
to create subnet prefixes. Guest VMs use this prefix to generate
their IPv6 global unicast addresses. For example:
$ nova network-create public --fixed-range-v4 10.0.1.0/24 --vlan 100 \
--vpn 1000 --fixed-range-v6 fd00:1::/48
Configuration option = Default value | Description |
---|---|
[DEFAULT] | |
fixed_range_v6 = fd00::/48 | (StrOpt) Fixed IPv6 address block |
gateway_v6 = None | (StrOpt) Default IPv6 gateway |
ipv6_backend = rfc2462 | (StrOpt) Backend to use for IPv6 generation |
use_ipv6 = False | (BoolOpt) Use IPv6 |
Compute uses a metadata service for virtual machine instances to
retrieve instance-specific data. Instances access the metadata service
at http://169.254.169.254
. The metadata service supports two sets of
APIs: an OpenStack metadata API and an EC2-compatible API. Both APIs are
versioned by date.
To retrieve a list of supported versions for the OpenStack metadata API,
make a GET request to http://169.254.169.254/openstack
:
$ curl http://169.254.169.254/openstack
2012-08-10
2013-04-04
2013-10-17
latest
To list supported versions for the EC2-compatible metadata API, make a
GET request to http://169.254.169.254
:
$ curl http://169.254.169.254
1.0
2007-01-19
2007-03-01
2007-08-29
2007-10-10
2007-12-15
2008-02-01
2008-09-01
2009-04-04
latest
If you write a consumer for one of these APIs, always attempt to access the most recent API version supported by your consumer first, then fall back to an earlier version if the most recent one is not available.
Metadata from the OpenStack API is distributed in JSON format. To
retrieve the metadata, make a GET request to
http://169.254.169.254/openstack/2012-08-10/meta_data.json
:
$ curl http://169.254.169.254/openstack/2012-08-10/meta_data.json
{
"uuid": "d8e02d56-2648-49a3-bf97-6be8f1204f38",
"availability_zone": "nova",
"hostname": "test.novalocal",
"launch_index": 0,
"meta": {
"priority": "low",
"role": "webserver"
},
"project_id": "f7ac731cc11f40efbc03a9f9e1d1d21f",
"public_keys": {
"mykey": "ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAAAgQDYVEprvtYJXVOBN0XNKV\
VRNCRX6BlnNbI+USLGais1sUWPwtSg7z9K9vhbYAPUZcq8c/s5S9dg5vTH\
bsiyPCIDOKyeHba4MUJq8Oh5b2i71/3BISpyxTBH/uZDHdslW2a+SrPDCe\
uMMoss9NFhBdKtDkdG9zyi0ibmCP6yMdEX8Q== Generated by Nova\n"
},
"name": "test"
}
Instances also retrieve user data (passed as the user_data
parameter
in the API call or by the --user_data
flag in the
openstack server create command) through the metadata service, by making a
GET request to http://169.254.169.254/openstack/2012-08-10/user_data
:
$ curl http://169.254.169.254/openstack/2012-08-10/user_data
#!/bin/bash
echo 'Extra user data here'
The metadata service has an API that is compatible with version 2009-04-04 of the Amazon EC2 metadata service. This means that virtual machine images designed for EC2 will work properly with OpenStack.
The EC2 API exposes a separate URL for each metadata element. Retrieve a
listing of these elements by making a GET query to
http://169.254.169.254/2009-04-04/meta-data/
:
$ curl http://169.254.169.254/2009-04-04/meta-data/
ami-id
ami-launch-index
ami-manifest-path
block-device-mapping/
hostname
instance-action
instance-id
instance-type
kernel-id
local-hostname
local-ipv4
placement/
public-hostname
public-ipv4
public-keys/
ramdisk-id
reservation-id
security-groups
$ curl http://169.254.169.254/2009-04-04/meta-data/block-device-mapping/
ami
$ curl http://169.254.169.254/2009-04-04/meta-data/placement/
availability-zone
$ curl http://169.254.169.254/2009-04-04/meta-data/public-keys/
0=mykey
Instances can retrieve the public SSH key (identified by keypair name
when a user requests a new instance) by making a GET request to
http://169.254.169.254/2009-04-04/meta-data/public-keys/0/openssh-key
:
$ curl http://169.254.169.254/2009-04-04/meta-data/public-keys/0/openssh-key
ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAAAgQDYVEprvtYJXVOBN0XNKVVRNCRX6BlnNbI+US\
LGais1sUWPwtSg7z9K9vhbYAPUZcq8c/s5S9dg5vTHbsiyPCIDOKyeHba4MUJq8Oh5b2i71/3B\
ISpyxTBH/uZDHdslW2a+SrPDCeuMMoss9NFhBdKtDkdG9zyi0ibmCP6yMdEX8Q== Generated\
by Nova
Instances can retrieve user data by making a GET request to
http://169.254.169.254/2009-04-04/user-data
:
$ curl http://169.254.169.254/2009-04-04/user-data
#!/bin/bash
echo 'Extra user data here'
The metadata service is implemented by either the nova-api
service or
the nova-api-metadata
service. Note that the nova-api-metadata
service
is generally only used when running in multi-host mode, as it retrieves
instance-specific metadata. If you are running the nova-api
service, you
must have metadata
as one of the elements listed in the
enabled_apis
configuration option in /etc/nova/nova.conf
. The
default enabled_apis
configuration setting includes the metadata
service, so you do not need to modify it.
Hosts access the service at 169.254.169.254:80
, and this is
translated to metadata_host:metadata_port
by an iptables rule
established by the nova-network
service. In multi-host mode, you can set
metadata_host
to 127.0.0.1
.
For instances to reach the metadata service, the nova-network
service
must configure iptables to NAT port 80
of the 169.254.169.254
address to the IP address specified in metadata_host
(this defaults
to $my_ip
, which is the IP address of the nova-network
service) and
port specified in metadata_port
(which defaults to 8775
) in
/etc/nova/nova.conf
.
Note
The metadata_host
configuration option must be an IP address,
not a host name.
The default Compute service settings assume that nova-network
and
nova-api
are running on the same host. If this is not the case, in the
/etc/nova/nova.conf
file on the host running nova-network
, set the
metadata_host
configuration option to the IP address of the host
where nova-api
is running.
Configuration option = Default value | Description |
---|---|
[DEFAULT] | |
metadata_cache_expiration = 15 | (IntOpt) Time in seconds to cache metadata; 0 to disable metadata caching entirely (not recommended). Increasing this should improve response times of the metadata API when under heavy load. Higher values may increase memory usage and result in longer times for host metadata changes to take effect. |
metadata_host = $my_ip | (StrOpt) The IP address for the metadata API server |
metadata_listen = 0.0.0.0 | (StrOpt) The IP address on which the metadata API will listen. |
metadata_listen_port = 8775 | (IntOpt) The port on which the metadata API will listen. |
metadata_manager = nova.api.manager.MetadataManager | (StrOpt) OpenStack metadata service manager |
metadata_port = 8775 | (IntOpt) The port for the metadata API port |
metadata_workers = None | (IntOpt) Number of workers for metadata service. The default will be the number of CPUs available. |
vendordata_driver = nova.api.metadata.vendordata_json.JsonFileVendorData | (StrOpt) Driver to use for vendor data |
vendordata_jsonfile_path = None | (StrOpt) File to load JSON formatted vendor data from |
You need to enable ping
and ssh
on your VMs for network access.
This can be done with either the nova or euca2ools
commands.
Note
Run these commands as root only if the credentials used to interact
with nova-api
are in /root/.bashrc
. If the EC2 credentials in
the .bashrc
file are for an unprivileged user, you must run
these commands as that user instead.
Enable ping and SSH with openstack security group rule create commands:
$ openstack security group rule create --protocol icmp default
$ openstack security group rule create --protocol tcp --dst-port 22:22 default
Enable ping and SSH with euca2ools
:
$ euca-authorize -P icmp -t -1:-1 -s 0.0.0.0/0 default
$ euca-authorize -P tcp -p 22 -s 0.0.0.0/0 default
If you have run these commands and still cannot ping or SSH your
instances, check the number of running dnsmasq
processes, there
should be two. If not, kill the processes and restart the service with
these commands:
# killall dnsmasq
# service nova-network restart
This section describes how to configure floating IP addresses with
nova-network
. For information about doing this with OpenStack
Networking, see L3 routing and NAT.
In this section, the term floating IP address is used to refer to an IP address, usually public, that you can dynamically add to a running virtual instance.
Every virtual instance is automatically assigned a private IP address. You can choose to assign a public (or floating) IP address instead. OpenStack Compute uses network address translation (NAT) to assign floating IPs to virtual instances.
To be able to assign a floating IP address, edit the
/etc/nova/nova.conf
file to specify which interface the
nova-network
service should bind public IP addresses to:
public_interface=VLAN100
If you make changes to the /etc/nova/nova.conf
file while the
nova-network
service is running, you will need to restart the service to
pick up the changes.
Note
Floating IPs are implemented by using a source NAT (SNAT rule in iptables), so security groups can sometimes display inconsistent behavior if VMs use their floating IP to communicate with other VMs, particularly on the same physical host. Traffic from VM to VM across the fixed network does not have this issue, and so this is the recommended setup. To ensure that traffic does not get SNATed to the floating range, explicitly set:
dmz_cidr=x.x.x.x/y
The x.x.x.x/y
value specifies the range of floating IPs for each
pool of floating IPs that you define. This configuration is also
required if the VMs in the source group have floating IPs.
IP forwarding is disabled by default on most Linux distributions. You will need to enable it in order to use floating IPs.
Note
IP forwarding only needs to be enabled on the nodes that run
nova-network
. However, you will need to enable it on all compute
nodes if you use multi_host
mode.
To check if IP forwarding is enabled, run:
$ cat /proc/sys/net/ipv4/ip_forward
0
Alternatively, run:
$ sysctl net.ipv4.ip_forward
net.ipv4.ip_forward = 0
In these examples, IP forwarding is disabled.
To enable IP forwarding dynamically, run:
# sysctl -w net.ipv4.ip_forward=1
Alternatively, run:
# echo 1 > /proc/sys/net/ipv4/ip_forward
To make the changes permanent, edit the /etc/sysctl.conf
file and
update the IP forwarding setting:
net.ipv4.ip_forward = 1
Save the file and run this command to apply the changes:
# sysctl -p
You can also apply the changes by restarting the network service:
on Ubuntu, Debian:
# /etc/init.d/networking restart
on RHEL, Fedora, CentOS, openSUSE and SLES:
# service network restart
Compute maintains a list of floating IP addresses that are available for assigning to instances. Use the nova-manage floating commands to perform floating IP operations:
Add entries to the list:
# nova-manage floating create --pool nova --ip_range 68.99.26.170/31
List the floating IP addresses in the pool:
# openstack floating ip list
Create specific floating IPs for either a single address or a subnet:
# nova-manage floating create --pool POOL_NAME --ip_range CIDR
Remove floating IP addresses using the same parameters as the create command:
# openstack floating ip delete CIDR
For more information about how administrators can associate floating IPs with instances, see Manage IP addresses in the OpenStack Administrator Guide.
You can configure nova-network
to automatically allocate and assign a
floating IP address to virtual instances when they are launched. Add
this line to the /etc/nova/nova.conf
file:
auto_assign_floating_ip=True
Save the file, and restart nova-network
Note
If this option is enabled, but all floating IP addresses have already been allocated, the openstack server create command will fail.
You cannot delete a network that has been associated to a project. This section describes the procedure for dissociating it so that it can be deleted.
In order to disassociate the network, you will need the ID of the project it has been associated to. To get the project ID, you will need to be an administrator.
Disassociate the network from the project using the nova-manage project scrub command, with the project ID as the final parameter:
# nova-manage project scrub --project ID
The multinic feature allows you to use more than one interface with your instances. This is useful in several scenarios:
Each VIP represents a separate network with its own IP block. Every network mode has its own set of changes regarding multinic usage:
In order to use multinic, create two networks, and attach them to the
project (named project
on the command line):
$ nova network-create first-net --fixed-range-v4 20.20.0.0/24 --project-id $your-project
$ nova network-create second-net --fixed-range-v4 20.20.10.0/24 --project-id $your-project
Each new instance will now receive two IP addresses from their respective DHCP servers:
$ openstack server list
+---------+----------+--------+-----------------------------------------+------------+
|ID | Name | Status | Networks | Image Name |
+---------+----------+--------+-----------------------------------------+------------+
| 1234... | MyServer | ACTIVE | network2=20.20.0.3; private=20.20.10.14 | cirros |
+---------+----------+--------+-----------------------------------------+------------+
Note
Make sure you start the second interface on the instance, or it won’t be reachable through the second IP.
This example demonstrates how to set up the interfaces within the instance. This is the configuration that needs to be applied inside the image.
Edit the /etc/network/interfaces
file:
# The loopback network interface
auto lo
iface lo inet loopback
auto eth0
iface eth0 inet dhcp
auto eth1
iface eth1 inet dhcp
If the Virtual Network Service Neutron is installed, you can specify the
networks to attach to the interfaces by using the --nic
flag with
the openstack server create command:
$ openstack server create --image ed8b2a37-5535-4a5f-a615-443513036d71 \
--flavor 1 --nic net-id=NETWORK1_ID --nic net-id=NETWORK2_ID test-vm1
You cannot reach your instances through the floating IP address.
Check that the default security group allows ICMP (ping) and SSH (port 22), so that you can reach the instances:
$ openstack security group rule list default
+--------------------------------------+-------------+-----------+-----------------+-----------------------+
| ID | IP Protocol | IP Range | Port Range | Remote Security Group |
+--------------------------------------+-------------+-----------+-----------------+-----------------------+
| 63536865-e5b6-4df1-bac5-ca6d97d8f54d | tcp | 0.0.0.0/0 | 22:22 | None |
| e9d3200f-647a-4293-a9fc-e65ceee189ae | icmp | 0.0.0.0/0 | type=1:code=-1 | None |
+--------------------------------------+-------------+-----------+-----------------+-----------------------+
Check the NAT rules have been added to iptables on the node that is
running nova-network
:
# iptables -L -nv -t nat
-A nova-network-PREROUTING -d 68.99.26.170/32 -j DNAT --to-destination 10.0.0.3
-A nova-network-floating-snat -s 10.0.0.3/32 -j SNAT --to-source 68.99.26.170
Check that the public address (68.99.26.170
in
this example), has been added to your public interface. You should
see the address in the listing when you use the ip addr command:
$ ip addr
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP qlen 1000
link/ether xx:xx:xx:17:4b:c2 brd ff:ff:ff:ff:ff:ff
inet 13.22.194.80/24 brd 13.22.194.255 scope global eth0
inet 68.99.26.170/32 scope global eth0
inet6 fe80::82b:2bf:fe1:4b2/64 scope link
valid_lft forever preferred_lft forever
Note
You cannot use SSH
to access an instance with a public IP from within
the same server because the routing configuration does not allow
it.
Use tcpdump
to identify if packets are being routed to the
inbound interface on the compute host. If the packets are reaching
the compute hosts but the connection is failing, the issue may be
that the packet is being dropped by reverse path filtering. Try
disabling reverse-path filtering on the inbound interface. For
example, if the inbound interface is eth2
, run:
# sysctl -w net.ipv4.conf.ETH2.rp_filter=0
If this solves the problem, add the following line to
/etc/sysctl.conf
so that the reverse-path filter is persistent:
net.ipv4.conf.rp_filter=0
Networking issues prevent administrators accessing or reaching VM’s through various pathways.
You can disable the firewall by setting this option
in /etc/nova/nova.conf
:
firewall_driver=nova.virt.firewall.NoopFirewallDriver
If you can access your instances with SSH
but the network to your instance
is slow, or if you find that running certain operations are slower than
they should be (for example, sudo
), packet loss could be occurring
on the connection to the instance.
Packet loss can be caused by Linux networking configuration settings
related to bridges. Certain settings can cause packets to be dropped
between the VLAN interface (for example, vlan100
) and the associated
bridge interface (for example, br100
) on the host running
nova-network
.
One way to check whether this is the problem is to open three terminals and run the following commands:
In the first terminal, on the host running nova-network
, use
tcpdump
on the VLAN interface to monitor DNS-related traffic
(UDP, port 53). As root, run:
# tcpdump -K -p -i vlan100 -v -vv udp port 53
In the second terminal, also on the host running nova-network
, use
tcpdump
to monitor DNS-related traffic on the bridge interface.
As root, run:
# tcpdump -K -p -i br100 -v -vv udp port 53
In the third terminal, use SSH
to access the instance and generate DNS
requests by using the nslookup command:
$ nslookup www.google.com
The symptoms may be intermittent, so try running nslookup multiple times. If the network configuration is correct, the command should return immediately each time. If it is not correct, the command hangs for several seconds before returning.
If the nslookup command sometimes hangs, and there are packets that appear in the first terminal but not the second, then the problem may be due to filtering done on the bridges. Try disabling filtering, and running these commands as root:
# sysctl -w net.bridge.bridge-nf-call-arptables=0
# sysctl -w net.bridge.bridge-nf-call-iptables=0
# sysctl -w net.bridge.bridge-nf-call-ip6tables=0
If this solves your issue, add the following line to
/etc/sysctl.conf
so that the changes are persistent:
net.bridge.bridge-nf-call-arptables=0
net.bridge.bridge-nf-call-iptables=0
net.bridge.bridge-nf-call-ip6tables=0
With KVM hypervisors, instances running Ubuntu 12.04 sometimes lose network connectivity after functioning properly for a period of time.
Try loading the vhost_net
kernel module as a workaround for this
issue (see bug
#997978)
. This kernel module may also improve network
performance on KVM. To load
the kernel module:
# modprobe vhost_net
Note
Loading the module has no effect on running instances.
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