[Rdo-list] Strange question: multiple NICs in VMs?

[Lars Kellogg-Stedman]

On Tue, Jan 06, 2015 at 03:23:12PM -0500, Dave Neary wrote:
> I am trying to automate the deployment of RDO on top of RDO, using
> OpenDaylight for networking - not for real work, just for validating the
> installation procedure.
> 
> I would like to have the instances I create in the OpenStack cloud to
> have 2 NICs each so that I can simulate a management & data network
> configuration, but I don't know how to create a virtual NIC in an
> instance (or even if this is possible, or maybe doesn't make any sense).

If you have multiple networks avaiable:

  $ nova net-list
  +--------------------------------------+----------+------+
  | ID                                   | Label    | CIDR |
  +--------------------------------------+----------+------+
  | ba4d7bd0-95de-4527-8ae8-c7f640fd2561 | net1     | None |
  | 02d13742-c783-4927-82df-bb7c30394f12 | ext-host | None |
  | 028d70dd-67b8-4901-8bdd-0c62b06cce2d | ext-nat  | None |
  | 18fc1b31-9b2c-4b6e-8dea-7e04bfd1eb43 | net0     | None |
  +--------------------------------------+----------+------+

Then when you boot an instance you can specify a NIC for each network:

  $ nova boot \
    --nic net-id=18fc1b31-9b2c-4b6e-8dea-7e04bfd1eb43 \
    --nic net-id=ba4d7bd0-95de-4527-8ae8-c7f640fd2561 \
    --flavor m1.small --image someimage my-nova-server

This would result in:

  $ ssh (ip address of my-nova-server)
  $ ip addr show
  1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN 
      link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
      inet 127.0.0.1/8 scope host lo
         valid_lft forever preferred_lft forever
      inet6 ::1/128 scope host 
         valid_lft forever preferred_lft forever
  2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
      link/ether fa:16:3e:4b:86:0f brd ff:ff:ff:ff:ff:ff
      inet 10.0.0.101/24 brd 10.0.0.255 scope global dynamic eth0
         valid_lft 86396sec preferred_lft 86396sec
      inet6 fe80::f816:3eff:fe4b:860f/64 scope link 
         valid_lft forever preferred_lft forever
  3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
      link/ether fa:16:3e:9a:f8:07 brd ff:ff:ff:ff:ff:ff
      inet 10.1.0.2/24 brd 10.1.0.255 scope global dynamic eth1
         valid_lft 86396sec preferred_lft 86396sec
      inet6 fe80::f816:3eff:fe9a:f807/64 scope link 
         valid_lft forever preferred_lft forever

You will want to make sure that either (a) you create all but one of
your subnets with --no-gateway or (b) you boot images that won't try
to use dhcp on all available interfaces, because otherwise you don't
know which interface will get used for the default route and things
like floating ip association may not functional properly.

-- 
Lars Kellogg-Stedman <lars at redhat.com> | larsks @ {freenode,twitter,github}
Cloud Engineering / OpenStack          | http://blog.oddbit.com/

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