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S-Series: how to get active-standby behaviour on LAG with two 10G-links?


Hi,
we want to connect two S-Series which are on two different sites. Both sites are connected with a direct and a backup connection, both are 10G. But the backup connection makes a longer way round so the latency is different.
Now we want to have a LAG which consists of these two links. But only the direct link should be active and when it fails, the backup link should become active.
We tried to work with LACP priorities but it seems this feature only works with different port speeds (f.e. priorize an 100MBit-Link higher than an 1GBit-Link).

Any ideas how to solve that problem?

4 replies

Userlevel 6
Hi Robert,
This cannot be solved using LACP.
Spanning tree could work, and one could manipulate the administrative port priorities to make the backup link go into standby (make it higher priority). One would need to be careful of course where to enable and disable spanning tree on site to site networks. It can either block a loop when enabled or create one if disabled without consideration of layer 2 redundancy.
Userlevel 6

Hi Mike,
thanks for your reply. We already considered Spanning Tree (and did use it in the past) but we really want to avoid it because it is suboptimal in our case and causes other issues.

Our primay goal in this case is to avoid different latency times. So a possible solution could be to define how many ports in the LAG go active, the other ports can be on Stand-By. Like the "lacp max-bundle" command from Cisco's IOS:

"To define the maximum number of active bundled LACP ports allowed in a port channel, use the lacp max-bundle command in interface configuration mode.
lacp max-bundle max-bundle-number
max-bundle-number : Maximum threshold of active member links allowed in the LACP bundle. The range from is 1 to 8."

With a command like that we could configure the S-Series like "put two ports into a LAG but only one shall be active at a time".

Feature Request. 🙂
Userlevel 2
Robert wrote:

Hi Mike,
thanks for your reply. We already considered Spanning Tree (and did use it in the past) but we really want to avoid it because it is suboptimal in our case and causes other issues.

Our primay goal in this case is to avoid different latency times. So a possible solution could be to define how many ports in the LAG go active, the other ports can be on Stand-By. Like the "lacp max-bundle" command from Cisco's IOS:

"To define the maximum number of active bundled LACP ports allowed in a port channel, use the lacp max-bundle command in interface configuration mode.
lacp max-bundle max-bundle-number
max-bundle-number : Maximum threshold of active member links allowed in the LACP bundle. The range from is 1 to 8."

With a command like that we could configure the S-Series like "put two ports into a LAG but only one shall be active at a time".

Feature Request. 🙂

This feature is not currently active in the S-Series and the customer is requesting this. Thank you! Please reference the new topic here: S-Series: active-standby behaviour on LAG with two 10G-links

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