An Unofficial Guide for Building a Network POC/DEV Lab without a Physical Switch/Router
Disclaimer & Assumptions
This documentation is not intended as best practice for a production environment. It is purely for lab development and proof-of-concept scenarios. The content does not describe configurations suitable for real-world deployment and should only be used for testing. It is assumed you already have basic knowledge of Data center & Enterprise network solutions, NAT, DHCP, Microsoft Domain controllers,PKI,and Vsphere client (vcenter). It is also taken that you have access to the appliance images and licenses (evaluation or perpetual ) required.
What Problem are we trying to solve?
The scenario here is you want to set up a lab at home or work but don't want to run too many hardware simultaneously. Perhaps, you plan to work during late hours and the thought of devices(switches,routers etc) whizzing and disturbing your family in the middle of the night puts you off from doing what you have to do, or you are onboarding new engineers in your team and would like to get them up to speed with the technology in your production environment without breaking anything. More importantly, you will like to reduce the cost of purchasing and powering these devices. If that sounds like you, please read on(and its not a very long one)
The challenge is to reduce the number of devices and minimize the power consumption of the lab, while still maintaining an environment that simulates a full-scale network((routers, Switches, Firewall, WLC,Access point,Data center to Data center connectivity, etc).)
Hopefully at the end of this article, you would have found valuable points to meet this challenge.
The Physical Components of the Lab
Here’s a description of the equipment referenced for this lab (and this is by no means a standard. Each lab environment will have its own unique requirements)
- X2 Blade Servers with ESXI running on each as type 1 hypervisor( choice of RAM/CPU/Disks should support your expected workload)
- Mac OS laptop with VMFusion type 2 hypervisior (Can be windows but prefer MAC for the flexibility of VMFusion)
- 1815T Teleworker AP for some wireless Technology ( any AP/Controller combination from other vendors according to your environment will do)
- An unmanaged switch/wireless router that connects you to the internet and serve as your Out of band management network(OOB). No managed switch is used in this guide.
Lets looks at the elements in the topology closely
- In the Vsphere client, there are 3x host making up the cluster (2xblades servers and 1 Mac PC) with OOB mgmt address at .19,.20 and .253 respectively on the 192.168.1.0/24 OOB network. The VCSA managing the host sits on the .253 host. Note that that you don't need a 3x host cluster for you to run things, A single host will do a job for you as long your have taken into resource utilization into account. In this Lab however, there are more than 13 network appliances running in the cluster including a catalyst center that demands 250GB of memory ! I will be focusing more on the .19 host as the .20 host is powered down at the time of producing this article (think cost savings)
- A default standard switch (see Fig1.9 further below) is used simply for external OOB management and internet connectivity. A distributed virtual switch( DS-Fabric) is setup in the vsphere client. Now, you can call this your aggregrator for the virtual networks in this lab. A point to note here is that this switch does not necessarily need a physical uplink to anywhere( to a physical switch or another host) for you to start deploying things. However, for interconnectivity between the hosts and for me to be be able to vMotion appliances across the 3 hosts smoothly, I have connected the two hosts together directly via their network interface card,vmnic7 (each blade server has 8 Nics). In Fig1.3, you can see that vminc7 is down because .20 is powered down .DS-Fabric has two uplinks,Uplink1 & Uplink-to-Mac (renamed that way for clarity)
- On the Mac(.253 host), the onboard Wifi card is the Nic1. I added a cheap network adapter via to the Mac to serve as Nic2(appears as vmnic1 in vsphere) and then simply map it under VMfusion settings( more straightforward in my opinion than Vmware workstation)
- In Fig1.3 &1.4, you can see .19 & .253 hosts uplinking into the DS-Fabric vSwitch (Uplink-to-Mac) via Nic7(appears as vmnic6 in vsphere) and Nic2(appears as vmnic1 in vsphere) respectively . You have guessed correctly, .19 hosts and .253 are directly connected via those Nics. There is a standby adapter to connect .253host to .20host if needed but for the purpose of this guide, lets assume it is not.
Notice in Fig1.6 that Nic2 got an IP address of 172.19.0.41/24. Where did that come from? I will come back to that in a second.
On the .253 esxi platform, there is a Microsoft 2022 server providing Domain controller, DNS,PKI.NTP services. You could also run DHCP but for the sake of this guide, DHCP is not running on this server. This server has two virtual Nics facing the External OOB management network (192.168.1.0/24) and the Nested OOB Management Network (172.19.0.0/24).
You should know that having two gateways on a windows client is not recommended and could lead to routing issues but again this is a lab and there is a design justification for doing this. This DC is essentially my link into both worlds(the physical and virtual network) .
There is a need to isolate some appliances in the lab meaning that they would not be using the external OOB network,which means the only way I can reach them from a jumpbox(my MGMT-PC) on the external network is to RDP into the DC and then access the isolated environment. I have also found that the routing issue with dual gateways becomes more noticeable when the gateways are hard coded. In Fig 1.7, I have mitigated that by making the IP assignment for the Nested-Virtual-Network-facing-Nic (Ethernet adapter 1) to be by DHCP (domain name appended in DHCP offer)
Now to the fun part, the network design. The most critical element in this is the Cloud service router (CSR1000v) that essentially builds and route for the nested virtual network. Note again that this network does not uplink to a physical switch, similar to what you will do in NSX-T with the overlay networks.The network stays inside vsphere except you introduce some other elements.
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Within the DS-Fabric, you create port groups,PG (that represents individual networks, you can also think of this as your VLAN on a physical switch if thats how you have setup). For this enviroment, VLAN tagging is inconsequential (but then again there is a twist to this, coming shortly).
I am treating each port group as layer3 point to point interface. Each interface on the CSR1kv is mapped to each PG. In Fig 1.8, Nic1(Gig1 on the router) is mapped to the 192-MGMT-19 PG.
This PG is the PG mapped to the standard switch for managing the host on the 192.168.1.0/24 network (Fig1.9 below)
Gig 1 on the CSR is my NAT egress to the internet and IP assignment for this specific interface is hard coded( default gateway for the CSR is the unmanaged Wireless Router at .254 and provides internet access)
I have configured DHCP pools with each pool having their default router as the router's interface mapped to that PG/network/IP Pool .Comparing Fig 1.8 and 2.0, you see that Gig2 is mapped to the 172-19-0-0-OOBMGMT PG and the interface has an ip of 172.19.0.1/24 which will also be the default gateway of any appliance whose NIC is attached to that PG within the vsphere environment
Now, going back to how the DC on .253 got the dhcp offer from the 172.19.0.0/24 pool
Remember what happens when you connect a device(say a pc) to a port without a specific Vlan assignment on a cisco switch. If a native vlan (assuming it is not left at vlan1) is configured on the trunk link and a dhcp server is active on that native vlan, the PC gets a dhcp offer from that native vlan pool. This article is not about native vlan and the nuances, so we leave it at that.
In the realm of the distributed switch Vpshere, if a vlan tag is not hardcoded on the PGs, they assume they are either routed interfaces(as we want them to be) or hope there is a native vlan in their uplink path.
That should normally not be an issue but for a non-vlan-aware device like the .253 host and the DC running on it, that may cause some confusion. Stay with me here!
Remember that all the interfaces on the CSR(apart from Gig1) are effectively an IP-helper interface , meaning that they will actively be looking to assist any client, that boots up without an IP address, get an IP . Also remember that because .253 has an uplink to the DS-Fabric vswitch ,So any VM running on it with a PG in that vswitch will be sending a DHCP request to all the interfaces on the CSR capable of attending DHCP requests because they all appear to the VM as one giant broadcast domain (which shouldn't). That means you are not guaranteed an IP lease from a specific PG/network/IP pool even if that's the only PG attached to the VM.
So in this case, which IP address does the DC VM get? The answer comes down to which interface on the CSR is the fastest to complete the DHCP offer(fastest finger first!) . I have tried this a couple of times and it is almost a round robin situation, you don't get same assignment on each VM boot especially if the DHCP lease time is very short.
If you are intentional about which IP gets assigned to which VM, this solution will not scale and can mess you around. However, there is a workaround.
From Fig1.7,you see that the DC gets the .42 address form the 19-SECURITY-MGMTpool and not from the ACI-INFRA pool and that is because I have tricked the ACI-OOB PG mapped to Gig4 on CSR to believe it is carrying a vlan tag ,a dummy vlan 998 (Fig2.1)
That vlan wont' get propagated anywhere as earlier noted unless you tweak things.
For the desired network(172.19.0.0/24) mapped to the PG to be associated to the DC VM, i have left the PG untagged which leaves the PG without any competition when it comes to DHCP offer. Your VM always comes on with the desired IP assignment.
You just have to ensure there is no other untagged PG in the same vswitch or you put a dummy vlan on the conflicting PG . Key thing to remember is that your router interface does the routing and your dhcp interface for any desired network you want to spin up.
In a future guide, I will be writing about setting up the Access point( with its own power source) to associate with a C9800CL without an intermediate physical switch. Your knowledge of the PG/untagged/tagged vlan will be crucial in implementing that. I hope this has been helpful.
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