[PATCH pve-docs v6 16/17] sdn: zones: document the MTU taken from the underlay interface

[Hannes Laimer <h.laimer@proxmox.com>]

Signed-off-by: Hannes Laimer <h.laimer@proxmox.com>
---
 pvesdn.adoc | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/pvesdn.adoc b/pvesdn.adoc
index 407986901ff2..24d4f967cf4d 100644
--- a/pvesdn.adoc
+++ b/pvesdn.adoc
@@ -308,7 +308,9 @@ SDN Fabric:: Instead of manually defining all the peers, use a
   xref:pvesdn_config_fabrics[Fabric] for automatically generating the peer list.
 
 MTU:: Because VXLAN encapsulation uses 50 bytes, the MTU needs to be 50 bytes
-  lower than the outgoing physical interface.
+  lower than the outgoing physical interface.  Optional, defaults to the MTU
+  configured on the interface holding this node's peer address minus 50 bytes.
+  Without such an interface or MTU, it defaults to 1450.
 
 
 [[pvesdn_zone_plugin_evpn]]
@@ -369,7 +371,9 @@ Route-target Import:: Allows you to import a list of external EVPN route
 
 MTU:: Because VXLAN encapsulation uses 50 bytes, the MTU needs to be 50 bytes
   less than the maximal MTU of the outgoing physical interface.  Optional,
-  defaults to 1450.
+  defaults to the MTU configured on the interface holding this node's address
+  from the controller's peers minus 50 bytes. Without such an interface or MTU,
+  it defaults to 1450.
 
 
 [[pvesdn_config_vnet]]
@@ -1762,7 +1766,8 @@ The example assumes a cluster with three nodes, with the node IP addresses
 192.168.0.1, 192.168.0.2 and 192.168.0.3.
 
 Create a VXLAN zone named `myvxlanzone` and add all IPs from the nodes to the
-peer address list. Use the default MTU of 1450 or configure accordingly.
+peer address list. Leave the MTU unset or configure accordingly. Without an MTU
+configured on the interfaces holding these addresses, the zone uses 1450.
 
 ----
 ID: myvxlanzone
-- 
2.47.3