DOC: Describe routing impact of using interface keyword on bind lines

diff --git a/doc/configuration.txt b/doc/configuration.txt
index 89421dbbca5d6e75e512cea64e34fc14b7fcd7fe..7cc5c13ceac6c592d3763767acb5badd19aa67ae 100644 (file)
--- a/doc/configuration.txt
+++ b/doc/configuration.txt
@@ -10799,7 +10799,12 @@ interface <interface>
   interface, not an aliased interface. It is also possible to bind multiple
   frontends to the same address if they are bound to different interfaces. Note
   that binding to a network interface requires root privileges. This parameter
-  is only compatible with TCPv4/TCPv6 sockets.
+  is only compatible with TCPv4/TCPv6 sockets. When specified, return traffic
+  uses the same interface as inbound traffic, and its associated routing table,
+  even if there are explicit routes through different interfaces configured.
+  This can prove useful to address asymmetric routing issues when the same
+  client IP addresses need to be able to reach frontends hosted on different
+  interfaces.
 
 level <level>
   This setting is used with the stats sockets only to restrict the nature of