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L2 Vlan with BGP

Metalpetrucci
Level 1
Level 1

Hi all, new here and still pretty new with networking...

I work in the broadcast industry and my company has been using Cisco Catalyst switches with VTP Client/server between Distribution and access switches.

Now the company is moving to Spine/leaf architecture with BGP protocol and VXLAN.

The question is:

With the old Catalyst switches and VTP, I have learned to be able to pass "Client networks" (network outside our own network) between switches by just created what I call a "dumb" VLAN, without SVI, and just assign that VLAN (passed through the VTP) to any port/any switch I need that network to.

Now with the Spine/Leaf architecture and BPG, is it possible to do that? Is it possible to pass this client network without assigning an IP to a port and using whatever IP the client is using on its devices?

If I create a VLAN without an IP and assign it to a VNI, do that on 2 leafs, would the client network passes?

Thank you for your answer and let me know if the question is not clear...

 

 

4 Replies 4

It sounds like previously you were carrying client network ethernet traffic by encapsulating the client frames in a VLAN tag and transparently forwarding (ie, without changing the frames) across your own L2 "core" network. In networking terms, the VLAN encap provided an overlay L2 tunneling service on top of an L2 underlay transport service.

At a high level, VXLAN is not too conceptually different from what you are already doing, though at a low-level the details are significantly different. With VXLAN, you still have an overlay service that transparently tunnels client (aka, tenant) ethernet frames over an underlay service, but in this case the overlay service is provided by encap'ing the client ethernet frames in IP/UDP for transport over an IP network (the underlay).

Native L2 underlay networks use control-plane protocols like STP and VTP to determine how to populate MAC address tables with MAC address, interface, and VLAN info to determine how to forward frames to the destination MAC address. L3 underlay networks have analogous IP routing tables containing IP address, interface, and VRF info. The IP routing tables are populated via static routes, dynamic routing protocols, and/or remote SDN controllers. Once you have the IP underlay service in place, there must be some mechanism in place for the L2 overlay service to determine how to connect together the L2 LAN segments around the edges of the network -- this is where BGP (BGP-EVPN) comes in as a control plane to propagate the L2 end-point info for the overlay service.

I would suggest deep-diving into the VXLAN data-plane and BGP-EVPN control plane by going over to the ciscolive.com site and searching for presentations using "VXLAN" as a search key. There you will see many video sessions from beginning to advanced topics that will be of more assistance than the few paragraphs I can write here.

Disclaimers: I am long in CSCO. Bad answers are my own fault as they are not AI generated.

Vxlan with bgp not need vtp.

Vlan must manually config in each SW and map it to vni.

Metalpetrucci
Level 1
Level 1

Thank you both for the answers. 

If I understand correctly, a device connected to a VLAN without an IP (SVI) will not be in the IP routing table so it will not be seen by other switches on the network through BGP. So VLANs need an IP to be mapped to VNIs or it is pointless?

I am really just trying to connect 2 devices from the "Client" using our network without having to re-IP their devices using some kind of trunking like encapsulation.

How about with VRFs. If I create a "Client" VRF on both leafs where those devices are connected to, would an IP still required to attached to a VN segment?

 

All I have learned so far about network is by using an eve-ng lab on Google cloud. Maybe I need to start that thing back up and just try different ways and see what happens. 

I really don't find much info online about BPG EVPN/VNI that talks about VLAN without SVI.

 

Thanks!

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