doc: document new MSDP filter command

Let user know how to use the MSDP SA filtering command

Signed-off-by: Rafael Zalamena <[email protected]>

doc/user/pim.rst

@@ -333,7 +333,7 @@ MSDP can be setup in different ways:
 
 .. note::
 
-   MSDP default peer and SA filtering is not implemented.
+   MSDP default peer is not implemented.
 
 
 Commands available for MSDP:
@@ -367,6 +367,15 @@ Commands available for MSDP:
 
    Create a regular MSDP session with peer using the specified source address.
 
+.. clicmd:: ip msdp peer A.B.C.D sa-filter ACL_NAME <in|out>
+
+   Configure incoming or outgoing SA filtering rule.
+
+   .. note::
+
+      The filtering will only take effect starting from the command
+      application.
+
 
 .. _show-pim-information: