Update README.md

README.md

@@ -175,7 +175,7 @@ OMD[build]:~$
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 ### Limitations
 
-- local/neighbour interface names have to match the service names in Checkmk
+- ~~local/neighbour interface names have to match the service names in Checkmk~~
 
 ---
 ### FAQ
@@ -323,6 +323,14 @@ Wehre `--path-in-inventory` is the path to your inventory data and `--inventory-
 
 </details>
 
+<details><summary>How are port names mapped to interface service names?</summary>
+
+\
+When mapping Layer 2 port names, the first step is to check whether the port name is in the host's list of interface items; if it is, the port name is used; if it is not, the port name is searched for in the inventory interface table. If found it tries to find the correct item by comparing the list of items with the fields index, description, alias, physical address (MAC) and (if available) [name](https://thl-cmk.hopto.org/gitlab/checkmk/vendor-independent/inventory/inv_ifname). If we still can't find the item, we pad the index and try the search again. 
+So most of the time we should find the correct interface service for a port.
+
+</details>
+
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 ### Sample Output