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intervlan communication using odl

asked 2014-08-22 04:58:37 -0800

ankit21a gravatar image

I am trying to set up communication between two vlans using ODL .can somebody please guide me here how we can achieve the same using Opendaylight.

Any document or link would be great.

Thanks in advance.

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Though it is really basic to get 2 hosts in different vlan to communicate with each other, the answer to your question depends on the switch that is in play and the protocols it support to communicate with OpenDaylight controller. Could you share a bit more details on the setup you are trying out ?

Madhu ( 2014-08-24 05:14:24 -0800 )edit

Hi Madhu, First off Thanks for your time and interest in this,I am using two type of switches 1. Legacy switches which supports netconf protocol 2. Openflow enabled switches, I have configured vlan on legacy switches using netconf protocol and on openflow switches using openflow protocol now that i am able to configure ,would like communicate between those switches with logic of intervlan communication.But i am bit new to this so need some guidance in this area.Please let me know how can i proceed to achieve the expected.

ankit21a ( 2014-08-24 06:24:24 -0800 )edit

Okay. But still there are a lot of missing pieces on the question :-(. But I will try to make some educated guesses and answer it. You may have to fill in the details to get a better answer.

Madhu ( 2014-08-24 07:22:04 -0800 )edit

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answered 2014-08-24 07:24:42 -0800

Madhu gravatar image

updated 2014-08-24 10:24:38 -0800

Based on the comments, I assume that the requirement is to get a host that is connected to a Traditional switch (which is controlled via NetConf protocol) on a particular Vlan (VlanX) to communicate with another host connected to an Openflow Switch on a different Vlan (VlanY). Ofcourse, there are more missing details. But I would make some educated guesses and try and answer this.

In traditional sense of Vlans, It provides a Bridging domain isolation & "typically" associated with a L3-Subnet. Hosts that belong to the same Vlan can bridge traffic between them without the need of a Gateway. And "Typically" Inter-vlan communication happens through L3-gateway which routes the traffic between 2 different L3-Subnet. (Since the Question was very general, I am assuming the above explanation as the basis, Please correct if your scenario is different). And there are traditional switches that supports X-Connect configurations which can connect Vlans directly (which is not a very common scenario).

In addition to this, there is also Port-Vlan-mode configurations such as Access, Trunk and Native which decides if the actual packet on the wire will carry the Vlan tag (using .1q) or not.

Whereas, In Openflow switches, Vlans are not-neccessarily seen the Traditional way. Since Openflow provides a flat space of flow-match/action, it can match on a given vlan and rewrite the packet to another Vlan without the need for any external router connectivity. That is purely from a switching point of view.

The Hosts networking stack, on the other hand would strictly follow a more traditional approach of always trying to reach an L3-Gateway whenever an inter-subnet reachability is expected. Again the assumption here is that, By inter-Vlan connectivity, I inherently assume you are trying to reach between 2 different subnets.

As you can see, there are a few scenarios / options / assumptions / configurations here. Without these cleared up, there wont be a more appropriate answer that would be helpful for everyone reading this. So, my recommendation would be to please update your question with more details (such as the ones I explained and that might lead to a better answer).

-- Answer edited based on the response --

With the above assumptions, the Host Networking stack will send ARP requests to the Gateway and hence we would need a Gateway present. This L3 Gateway can either be configured on the Traditional Switch/Router and that performs the routing between the 2 vlans. In this scenario, the Openflow Switch acts purely like a L2 Bridge and just bridges the traffic to the Host. Please note that pure L2 switches dont really care about ARP processing and they just flood the ARP requests and perform Mac learning. In the case of openflow switches, we can either do it reactively via Controller programming these Mac-addresses (or) Proactively through other means.

On the other hand, if you prefer to use the L3 Gateway functionality of The ODL controller, then you would have to use the Subnet Gateway feature along with Simple Forwarding Application. Please refer to https ... (more)

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Yes the scenario you are assuming is correct and i am using juniper switches as my legacy switches which i think do not support x-connect and supports port vlan mode to carry vlan tags. if i understand correctly you are suggesting open flow switches will be able to send /write packet to other host on different vlan but dont we need to initiate the process with sending ARP packets to the switches.Pls correct me if i am wrong. Yes here again you assumption is correct for Host networking stack i am trying to reach between two different subnets. i hope i am still not missing something let me know if i am, sorry for that

ankit21a ( 2014-08-24 10:12:58 -0800 )edit
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Asked: 2014-08-22 04:58:37 -0800

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Last updated: Aug 24 '14