Creating a Dynamic Lab Environment with vEOS and GNS3 - Part II

SETTING UP A DHCP AND FILE SERVER FOR USE WITH ZTP

Now that we have a couple vEOS instances configured and able to communicate, and we have our out-of-band network set up, we can now begin to use ZTP to provide an initial startup config.

NOTE Notice that we did not connect the Management1 interface of either vEOS instance to anything inside of GNS3.  If you remember when we created the VMs, their first interface is a host-only adapter connected to the vboxnet in VirtualBox, so it’s automatically connected and there’s nothing additional we need to do there, but GNS3 doesn’t know that so it considers the interface disconnected, and that’s OK.  That saves us from having to add our management server(s) to the topology and cluttering it up (Just imagine trying to have a nice clean-looking topology in GNS3 if you had to have a connection from every vEOS instance to the management server(s) ), which is distracting and ugly - we’re better than that.

ZTP is enabled as a default on the vEOS instances, but we still need to set up a server to provide DHCP and File services.  For servers, Ubuntu is my go-to and I usually work with them in VirtualBox the same way I do with vEOS - I create a base image that is my raw golden standard and then create clones from it.

In this case, I already have a base image that is running Ubuntu Server 14.04.1 LTS, so I’ll go ahead and create a clone of that to work with.  For this server we’ll want one adapter connected to the vboxnet, and another adapter attached to NAT so that we can download and install DHCP and File services:

TIP! Something I’ve found handy is to edit the description of my server VMs in VirtualBox to reflect what they have installed.  For example, my server base image has the following description: BASE IMAGE - Ubuntu Server 14.04.1 LTS ========================================== ifenslave-2.6 (NIC Bonding, LACP) iperf 2.0.5-3 The description can be accessed in the VM settings under General > Description

Your NAT interface should get an IP address automatically, but you’ll need to edit /etc/network/interfaces in order to statically-set the IP address in your management subnet (vboxnet) for your host-only adapter:

# This file describes the network interfaces available on your system

# and how to activate them. For more information, see interfaces(5).

# The loopback network interface

auto lo

iface lo inet loopback

# The primary network interface

auto eth0

iface eth0 inet dhcp

auto eth1

iface eth1 inet static

address 172.16.128.254

netmask 255.255.255.0

TIP! Always make a backup of the file you’re going to edit before doing so, so that you’ll have a copy of the original in case you make a mistake and need to start over.  For example, when I’m backing up the original of a file I’ll do something like: sudo cp /etc/network/interfaces /etc/network/interfaces.orig And for future temporary backups I’ll just do: sudo cp /etc/network/interfaces /etc/network/interfaces.old Also, for servers that will go back and forth between different interface configurations, I’ll make backups of each config, for example: sudo cp /etc/network/interfaces /etc/network/interfaces.BOND This way, when I go from a configuration that isn’t using NIC bonding to a configuration with NIC bonding, I can just do something like the following instead of manually re-configuring the file each time: sudo cp /etc/network/interfaces.BOND /etc/network/interfaces

Installing and Configuring DHCP Services

Once you’ve verified IP addressing is good to go, update your package lists with the sudo apt-get update command, then install the ISC DHCP server by using sudo apt-get install isc-dhcp-server. Then we’ll need to modify the /etc/dhcp/dhcpd.conf file.  Here is a basic dhcpd.conf file you can use, substituting as necessary:

ddns-update-style none;

default-lease-time 600;

max-lease-time 7200;

log-facility local7;

subnet 172.16.128.0 netmask 255.255.255.0 {

 option subnet-mask 255.255.255.0;

 range 172.16.128.100 172.16.128.200;

}

host SPINE1 {

 #option dhcp-client-identifier 08:00:27:51:2b:4b;

 hardware ethernet 08:00:27:51:2b:4b;

 #fixed-address 172.16.128.21

 option bootfile-name "http://172.16.128.254/spine1_cfg";

}

As you can see, the subnet configuration represents our management network.  The host configuration is really the meat & potatoes of the ZTP configuration.  For the “hardware ethernet” field, enter the MAC address of the Management1 interface of your vEOS instance, which can be retrieved by using show int ma1 command:

The last line of the host configuration represents the location of the bootfile, which will be on the same server (after we install and configure it first of course). You may have also noticed two lines in the host configuration that are commented out - I’ve included these for reference - the client-identifier is something we’d use for a real switch, but not needed here.  The fixed-address won’t be needed here either - we’ll just let the DHCP server give it a temporary IP from the pool and instead include its management IP in a configuration file that the file server will provide.  After the dhcpd.conf file is modified, start the DHCP server using the sudo service isc-dhcp-server start command.

NOTE Any time you modify the dhcpd.conf file in the future, you will need to restart the service with the sudo service isc-dhcp-server restart command for the changes to take effect

Installing and Configuring File Services

Now we’ll need file services.  For this I prefer Apache, which can be installed by using sudo apt-get install apache2.  The default location for files to be shared is /var/www/html, so in that location we will create a file called “spine1_cfg”, and provide a basic configuration, for example:

hostname SPINE1

!

aaa authorization exec default local

!

aaa authentication policy local allow-nopassword-remote-login

!

username admin privilege 15 role network-admin nopassword

username eapi privilege 15 secret password

!

interface Management1

  ip address 172.16.128.21/24

!

management api http-commands

  no shutdown

!

banner login

******************************

***  SPINE1 LOGIN BANNER   ***

******************************

EOF

!

banner motd

*****************************

***  SPINE1 MOTD BANNER   ***

*****************************

EOF

!

end

At this point we should have everything we need to verify functionality of ZTP - it’s the moment of truth.  Use the erase startup-config command followed by reload now to reload the vEOS instance with no startup configuration, which will trigger ZTP:

What we want to see is a successful DHCP process followed by the switch pulling down it’s basic config file and then rebooting:

So in this case, the vEOS instance was assigned a temporary IP of 172.16.128.100 from the pool, which allowed it to reach the file server at 172.16.128.254 to download its configuration file before finally rebooting.  Once the instance finishes rebooting, we can verify that ZTP was successful simply by the fact we can see the hostname and login banner:

Congratulations - you’ve just done your first automated “bare-metal” provisioning with ZTP!  Now you have a good reference config to work off of - just copy the spine1_cfg file as many times as needed for each vEOS instance, modify the appropriate fields (Mgmt IP address, hostname, etc.), and you’re good to go.  Don’t forget that you’ll also need to add the appropriate DHCP host configurations as well.

Creating a Dynamic Lab Environment with vEOS and GNS3 - Part I

GETTING STARTED

Preliminary Installation Setup

Install GNS3

Install VirtualBox

Get ahold of the .vmdk and aboot.iso files

It is recommended to install VirtualBox AFTER you install GNS3 to avoid problems with GNS3 detecting VirtualBox.

Go to www.arista.com, and go to Support > Software Download.  The two files you’ll want are the .vmdk file as well as the Aboot .iso file:

Creating the Management Network

To simulate an out-of-band management network, we will create a vboxnet interface, similar to a loopback interface, on our laptop.  This will also allow us to interact with our virtual machines via SSH, etc.

Open VirtualBox, go to Preferences, and click Network. Select “Host-only Networks”, and then click the NIC adapter image with a plus symbol on it to add a new host-only network if there isn’t one already:

Select your newly-created vboxnet and click the screwdriver icon to configure it:

We’re going to be using ZTP to provision our switches, so select “DHCP Server”, ensure “Enable Server” is unchecked, and then click OK:

Verify you have a new interface reflecting your vboxnet configuration:

SETTING UP vEOS

Creating a Base Image

You’ll want a nice, clean base image to create clones from.  

To begin, in VirtualBox, click New:

Give your base image a name.  Use the drop-down menus to set the Type to “Linux”, the Version to “Other Linux (64-bit)”, and then click Continue:

Set the memory allocation to 2048, and then click Continue:

Select “Use an existing virtual hard disk file”, select the .vmdk file you downloaded earlier, and click Create:

Our base image has been created, but now must be configured.  Select the new base image, and click Settings:

Click Storage, and then use the drop-down menu to set the second entry under “Controller: IDE” to IDE Secondary Master, then click the small CD icon and select the Aboot.iso file downloaded earlier

Click Network, select Adapter 1, ensure “Enable Network Adapter” is checked, and use the drop-down menu to select “Host-only Adapter”.  Ensure the Name is populated with the management network created in the previous section, use the drop-down menu to set the Adapter Type is set to “PCnet-FAST III”, and ensure that “Cable Connected” is checked. Click OK to save your changes:

Leave the rest of the Adapters alone - these will be configured for you by GNS3 later.

Verify your base image settings and launch the VM to verify it successfully boots:

TIP! At this point, you have a decision to make.  You can either leave the base image as-is and configure everything on the clones that you will make, or if there’s something that will be configured on every clone, such as a username, you could configure this in your base image so that you won’t have to do it on your clones.  For our lab though, we’re going to be provisioning everything with ZTP and Ansible, so I’m going to leave the base image as raw as possible. If you noticed, we created a host-only adapter in our base image so that every time we create a clone, it will already have its first adapter be its management connection.  You’ll see why later.

Creating Clones

If you haven’t already, shut down your base image.  Now, in VirtualBox, right-click it and select “Clone”.  Click “Expert Mode” - because you’re clearly too awesome for that guided nonsense (And doing it this way is just quicker).  Give your clone a name, ensure that “Full Clone” and “Reinitialize the MAC address of all network cards” is selected, and then click Clone - repeat as necessary to create additional clones:

WARNING! This part is very important.  If you select “Linked Clone”, your clone will be linked to the base image instead of creating its own file.  This means if you accidentally choose to delete all files when you delete your clone later, it will also effectively delete your base image as well.   If you do not select “Reinitialize the MAC address of all network cards”, all clones will have the same MAC address as your base image, and you can imagine the fun that will create in your virtual network.

GETTING STARTED IN GNS3

Adding VMs to GNS3

GNS3 has very tight integration with VirtualBox.  As you create connections between your vEOS instances, server VMs, etc., GNS3 takes care of all configuration needed on your VirtualBox VMs for you - no manual configuration needed inside of VirtualBox itself for each new connection.  

To get started, we’ll need to add our newly-minted cloned vEOS instances to GNS3.  Open GNS3, start a new project, and then open Preferences.  Go to VirtualBox > VirtualBox VMs, click New, use the drop-down menu to select your newly-created clones, and then click Finish - repeat as necessary:

Select your VM and click Edit. Under “Network”, configure the following and then click Ok, repeating as necessary for each VM:

NOTE At the time of this writing, VirtualBox can support a maximum of 8 adapters.  Refer to the article in “Resources/Recommended Reading” for details.  The first adapter will be your management interface, hence the “First port name:”, and then you’ll have an additional 7 interfaces to play with.

TIP! If you want your VM to cosmetically appear more like a switch in GNS3, under “General Settings”, set the Category to “Switches”, and change the Symbol to “Multilayer Switch”.

Click Apply, and then click OK to exit.

Now that our vEOS VMs are configured in GNS3, we can start building our virtual network. On the main project screen, click “Browse All Devices”, and then drag-and-drop your VMs onto the topology panel (the center panel):

Click “Add a Link”, click one VM, select “Ethernet1”, and connect it to your other VM on the same interface:

Click “Start/Resume all devices”, and when the VMs are finished booting, setup some VLANs and SVIs and verify you have connectivity:

Great!  Let’s move on to providing “bare-metal” provisioning with ZTP.