Generate Link-Local Mapping for VMs on Tungsten Fabric

Lately, I’ve been fiddling around with Juniper Contrail (Available as Upstream project: Tungsten Fabric). So, I’ll be posting about different stuff I learn about it, SDN in general, and Openstack as well.

One thing that I find myself doing often is testing connectivity between different network resources, primarily VMs. To do so, sometimes I need to test end-to-end connectivity which requires accessing the VM and initiating something as simple as a ping command to see what happens.

However, VNC Console (Or direct connectivity from my workstation towards Overlay/Virtual Networks that virtual machines are connected to may not be available. For this, I need to connect to the VM using the link-local IP address directly from the vRouter / Compute node.

I wrote a python script that uses Contrail API Introspect service to fetch info about compute nodes, then prints the info for VMs hosted on each one of them. In this example, I need to access a VM called AAP_02, so I use the script to find on which vRouter / Compute node it is hosted, then access it directly from there without needing to source Openstack credentials:

[root@contrail-controller contrail_utils]# python vm_linklocal_info.py
+------------------------------+-------------------+----------------+-------------------+---------------------+
|         Compute Node         |      VM Name      | VM IP Address  |   VM MAC Address  | VM Metadata Address |
+------------------------------+-------------------+----------------+-------------------+---------------------+
| contrail-vrouter02.ameen.lab |    XRR_01_Main    |  172.16.0.67   | 02:05:94:e1:f0:fd |     169.254.0.4     |
| contrail-vrouter02.ameen.lab |   XRR_02_Changed  |   172.16.0.4   | 02:6b:5e:1a:3c:5b |     169.254.0.3     |
| contrail-vrouter02.ameen.lab |       AAP_02      |  172.16.0.69   | 02:f2:8c:53:6a:2d |     169.254.0.5     |
| contrail-vrouter03.ameen.lab |    XRR_01_Fixed   |   172.16.0.3   | 02:7a:85:f8:de:a1 |     169.254.0.3     |
| contrail-vrouter03.ameen.lab |       AAP_01      |  172.16.0.68   | 02:97:bc:7d:bf:79 |     169.254.0.5     |
| contrail-vrouter03.ameen.lab | vXRR_CrossProject |  172.16.0.131  | 02:97:f1:03:79:f0 |     169.254.0.4     |
+------------------------------+-------------------+----------------+-------------------+---------------------+

[root@contrail-controller contrail_utils]# ssh contrail-vrouter02.ameen.lab
root@contrail-vrouter02.ameen.lab's password: 

[root@contrail-vrouter02 ~]# ssh root@169.254.0.5
root@169.254.0.5's password: 

[root@AAP_02 ~]# ip address show eth0 
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP>; mtu 1500 qdisc pfifo_fast state UP qlen 1000
    link/ether 02:f2:8c:53:6a:2d brd ff:ff:ff:ff:ff:ff
    inet 172.16.0.69/26 brd 172.16.0.127 scope global eth0
       valid_lft forever preferred_lft forever

Script is available here. Clone it to your Contrail Controller and execute it from there.