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

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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?
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Posted 4 years ago

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Mike Thomas, Employee - GTAC - NMS

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Official Response
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.