LAG link between 2 netgear switches

Posted on 2013-02-07
Last Modified: 2015-05-24
Hello all,

We currently have 2 x netgear GS748TPS switches connected via HDMI (stacked), these were in place before I got here and there are multiple VLANS configured - among them the clients and the servers VLANS and upto now they route to each other via the edge firewall (checkpoint). So all traffic between the VLANS is running up a single cable to the firewall and back down it - not great. We also have no control over the checkpoint firewall (head office controlled) which makes config changes a nightmare.

So we now have a Netgear GSM7328S layer 3 switch to allow routing to occur before the firewall, but the switch will not stack natively with the existing switches and we need a decent level of bandwidth.

So the plan is to link them with 4 links setup in a LAG giving a 4Gbps link.

Here is the issue, the settings for the LAG on the different switches are wildly different, on the layer 2 switch its quite basic with not many options but on the layer 3 switch we have a number of settings to decide on:

GSM7328S LAG options
Could someone with more experience help out here, what will be best in order to give us a higher capacity link between the switches?

Oh and all VLANS on both switches match and are tagged on the LAG port (except VLAN1)
Question by:duddit2
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Author Comment

ID: 38863164
To follow up, I had issues getting the LAG to come up and called Netgear support who said that static should be enabled, this worked but once it came up I couldn't manage the switch.

I think this was some king of looping issue, as my machine is connected to the stacked switches on VLAN100, and in order to get to the new switch a single cable is connected between the layer 2 and layer 3 switch (in addition to the 4 cables for the LAG), VLAN100 is tagged on the single link and this VLAN is setup for routing so has an IP address on the new switch which is used for management.

When the LAG came up this network subnet just started to lag massively (to the point where it was unusable) so I had to get someone onsite to unplug the LAG cables - I think this was some looping issue.
LVL 21

Expert Comment

ID: 38864081
I think you need to set STP Mode to enable, in the LAG config screen, to get the LAG to participate properly in spanning tree to fix the loop problem.

However, spanning tree will then block either the LAG or the original port between switches by design.

So you should configure the LAG to exactly match the config for the interconnecting port or use that port as one of the LAG ports and just add 3 other ports to it.
This is a new switch so that shouldn't be an issue right?

If the L2 switch is LACP capable that may be a good way to go and let the protocol take care of forming and managing the LAG instead of configuring everything statically.

Accepted Solution

duddit2 earned 0 total points
ID: 38866444
The only way I could get this to work is to set the LAG as static, even though the layer 2 switch supports LACP.

STP is off as well.

If anyone else can think of a reason why static seems to be my only option (or if it even matters) then please let me know.

The main issues I now face are reconfiguring routing on a live network remotely, but that's another issue :)
LVL 17

Expert Comment

ID: 38872599
Reading through the GS7xxTS manual, they don't explicitly mention that you can do a multi-chassis/distributed LAG. Are you sure it works on those switches?


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