MLAG / MC-LAG Functionality?

[uberdome]

By any chance does the Vitesse switch core support MLAG / MC-LAG functionality? If so, are there any current plans to implement that functionality?

If not, is it being considered for other future products?

[I've been experimenting with MLAG on a small scale in an effort to build very high reliability small sites. All of the hardware I've found that supports it at a reasonable cost is way too power hungry to make sense at a smaller site.]

[mike99]

You will be able to do redundancy with fast convergence with ERPS currently in beta phase for setup over 2 switchs.

[uberdome]

That works for redundancy with a group of switches, but it does not help with redundancy between devices [that support LAG] and switches.

[Eric Stern]

As near as I can tell there is no standard implementation for MC-LAG. We could possibly implement our own version of it (I can't tell if the switch core supports it, but there is no mention of it in the documentation) but it would not interoperate with other vendors equipment.

[uberdome]

That is my understanding as well. Each vendor has their own implementation MC-LAG (under many names). This generally allows a LAG to be configured from a single device to the switches that support it. This allows aggregation to function through two separate switches, so if one fails, the link capability is cut in half rather than being shut down entirely.

Generally, the MC-LAG component is vendor specific, but that MC-LAG can connect to any device that supports standard LAG connections.

[sirhc]

I do this with LACP LAG unless I am missing something?
I use 2 ports between my switches at our NOC to form an LACP LAG.

I can remove 1 cable and the traffic drops to 1 port then when I put the cable back in traffic splits across the 2 ports.

Now sadly I use Cisco routers at my towers which do not support LACP so I have to use Static LAGs which if 1 port/channel drops all hell breaks out as half the traffic is lost but so far this has never happened except under testing.

[mike99]

He want the 2 ports of the lag to be on different switchs. The LAG device would be still reachable in case of switch failure or maintenance.

Here a picture that explain LAG (between the device and switch) with MC-LAG (between switch):
http://1.bp.blogspot.com/-UrWYIoecIkM/T ... titled.GIF

The device redundancy could also be done via RSTP (if device also support it) but LAG is active/active while RSTP is active/passive. The downside is that RSTP couldn't pass over an ERPS ring unless using an L2 encapsulation like EPL or L2PT.

P.S. (off topic): L2PT is probably support by the vitesse chip and could lead L2 VPN service to a next level since QinQ can't forward STP and discovery protocols.

[uberdome]

Exactly, what Mike said. You can run two switches that are connected together and configured in a way that allows LAG legs to be distributed between those two switches. Then you can run a router with a LAG connection that connects to each of the switches, so if one switch fails or is updating, the other half of the LAG continues to function.

[uberdome]

Thinking about it further, another option would be to support stacking with LAG legs allowed to be distributed between stack members.

Usually the simplest form of MC-LAG is two separately managed switches that support splitting a LAG for redundancy purposes. While one is out of service or is being serviced, the other continues to function (including during a configuration error).

The simplest form of split LAG on a stack is two stacked switches that are managed as one unit that support splitting a LAG for redundancy purposes. It seems this is possibly less reliable (if the switch configuration is somehow altered, the whole stack stops working correctly), but Netonix has a good "make sure it works before really committing" process.

It seems the larger switch manufacturers more often support stacking than they do MC-LAG, so perhaps stacking would be a more useful feature while providing a similar functionality. The Juniper units I'm experimenting with right now allow stacking with any of the front ports (including bonds).

[uberdome]

Eric, does the switch core support stacking?