topic Re: Semantics of untagged VLAN with relation to LLDP and OpenFlow instances in Software Defined Networking

Semantics of untagged VLAN with relation to LLDP and OpenFlow instances

phpHavok — Thu, 29 Sep 2016 17:13:16 GMT

Through testing, I have found that LLDP packets traverse links between two HP devices untagged. This has raised some questions, so let me present a scenario. Consider two switches A and B connected by a link (say between port 1 on both switches). Let A port 1 and B port 1 be both configured as follows: tagged VLAN 2, no untagged VLANs. LLDP packets will traverse the link and be processed by both switches. However, being that LLDP packets are sent untagged, how are they processed? Is a packet automatically associated with some special VLAN if it arrives untagged on a port with no native VLAN? The relation here to OpenFlow is that if I want to send LLDP packets to the controller, it seems that I cannot. Even an aggregate OpenFlow instance will not receive these tagless packets. What is going on here?

Thanks!

Re: Semantics of untagged VLAN with relation to LLDP and OpenFlow instances

Scott_Koster — Tue, 04 Oct 2016 19:52:50 GMT

Your testing is providing correct results. LLDP frames are sent untagged and if there is no OpenFlow enabled untagged vlan the LLDP frames will cannot be matched on in the OpenFlow pipeline.

For your network, you'll need to design in an OpenFlow enabled untagged vlan. All switches can support any arbitrary untagged vlan, so the best I can say on this is to change one of the vlans that is currently tagged to untagged on both switches.

Re: Semantics of untagged VLAN with relation to LLDP and OpenFlow instances

phpHavok — Fri, 07 Oct 2016 20:00:01 GMT

Thanks!