What needs more bandwidth, The MLAG connections of the switch interconnects?

What traffic actually flows across the peer to peer links?  I have it set up but if I disconnect both partner links to one switch the links go down for the host machine on that switch. I thought mlag worked like VLTi.

The S4810 and N4000 switches suggest using the 40Gb connections for the peer to peer connection(VLTi). I am sure with the N3000 the same would apply in that you would want to use the 10Gb connections for peer to peer. However I think the hardware you have on hand may dictate how you set this up. The S4810 is a 10/40 Gb switch. So if all you have are 10Gb ports on the S4810, then you will be forced to use the 10Gb ports on the N3000 for that connection. Then your MLAG peer to peer link you would use multiple 1Gb ports, adding up to 8 total.

If you have 1Gb transceivers for the S4810, then you could set the LAG up with four 1Gb connections. And then use the 10Gb connections on the N3000 for peer to peer connection.

Here is the latest MLAG document with some configuration examples.

http://dell.to/1IpFYpV

Hope this helps.

The peer-link is used for the following purposes:

• To transport keep-alive messages to the peer.

• To sync FDB entries learned on MLAG interfaces between the two MLAG peer switches.

• To forward STP BPDUs and LACPDUs received on secondary MLAG member ports to the primary  MLAG switch.

• To send interface events related to MLAG interface and member ports that occur on the secondary switch to the primary switch.

• To transfer MLAG control information between the primary and secondary MLAG switches.

• Support a redundant forwarding plane in the case that all member ports of an MLAG interface are down on an MLAG peer. In this case, traffic received on the peer switch destined to the MLAG peer with the downed ports is sent over the peer-link to the peer MLAG switch for forwarding to the partner switch.

Is your host machine an orphan or does it have an MLAG going to the two N3000 switches? Are there multiple VLANs? If so are those VLANs on the the Peer link interface configuration?

it is an orphan. There are multiple VLANs but it is isolated on one vlan for testing. The VLAN is set to be tagged on all Port channels and LAGs.

What does not seem to be working is the last bullet point. So really it should work just like VLTi and I should be able to unplug all partner links to switch A and traffic should forward through peer B to Peer A.

So from what I have been reading  if you have hosts connected to the peers they have to be connected to each peer and not a single connection to one or the other peer? No orphans on either switch as traffic is not passed through to the mlag.  I think with VLTI you can have orphans?

Correct, that is only with orphaned devices though. If the device is configured with a MLAG and one of the partner switch loses both connections, the device will still have connectivity. If your network design has mostly end devices plugging into the N3000 switches, then MLAG is probably not be the best suited.

So orphaned devices will work on the partner connections as long as one of them is up, it just won't work across the MLAG if both partner connections on one peer goes down? Correct?  I don't see the benefit of mlag then if you have to have the partners in a mesh config anyways. it is unlikely you would lose both connections to two different switches, at least not in our environment.

Yeah, orphaned/single homed devices are not supported right now. There are some workarounds listed in section 6, page 19, of the MLAG document. I believe that in future firmware there are supposed to be some improvements on this, but I don't have any specifics.

Hi Daniel,

I'm trying to understand mlag use cases in storage network (iscsi/vsan) and active/passive NIC teaming for servers either windows 2012 (native teaming) or vmware (vswitch teaming). 

• Support a redundant forwarding plane in the case that all member ports of an MLAG interface are down on an MLAG peer. In this case, traffic received on the peer switch destined to the MLAG peer with the downed ports is sent over the peer-link to the peer MLAG switch for forwarding to the partner switch.

With the information above; does vpc peer link carry/flow the vlans/network traffics like regular lag connection between n series or similar to vlt in force10?

I really appreciate any help you can provide.

With the N-series and MLAG, the peer link is only going to carry vlan/network traffic when a link is down on one of the peers. Where as with VLT, the vlan/network traffic can always traverse this connection. This results in MLAG not supporting single homed devices, and VLT supporting single homed devices.

Thank you very much for the clarification.