doc: Start talking about useful sysctl's for proper zebra operation

Add some color to useful sysctl's that are needed for FRR proper operation.

Signed-off-by: Donald Sharp <sharpd@nvidia.com>

diff --git a/doc/user/Useful_Sysctl_Settings.md b/doc/user/Useful_Sysctl_Settings.md
index 4244b5fdfb5b76e5bce7397c322af0cc389c9dda..eaf97b969cc78e5430773284093d0313db557c12 100644 (file)
--- a/doc/user/Useful_Sysctl_Settings.md
+++ b/doc/user/Useful_Sysctl_Settings.md
@@ -37,6 +37,7 @@ net.ipv4.icmp_errors_use_inbound_ifaddr=1
 
 #   Keep ipv6 permanent addresses on an admin down
 net.ipv6.conf.all.keep_addr_on_down=1
+net.ipv6.route.skip_notify_on_dev_down=1
 
 # igmp
 net.ipv4.igmp_max_memberships=1000

diff --git a/doc/user/zebra.rst b/doc/user/zebra.rst
index 205b25e53e04461de82857bfbbbf3648187a5fea..2b23d5e464e9343b2d2b7b280485300508306ca8 100644 (file)
--- a/doc/user/zebra.rst
+++ b/doc/user/zebra.rst
@@ -1021,6 +1021,35 @@ For protocols requiring an IPv6 router-id, the following commands are available:
 
    Display the user configured IPv6 router-id.
 
+Expected sysctl settings
+========================
+
+The linux kernel has a variety of sysctl's that affect it's operation as a router.  This
+section is meant to act as a starting point for those sysctl's that must be used in
+order to provide FRR with smooth operation as a router.  This section is not meant
+as the full documentation for sysctl's.  The operator must use the sysctl documentation
+with the linux kernel for that.
+
+.. option:: net.ipv4.ip_forward = 1
+
+   This option allows the linux kernel to forward ipv4 packets incoming from one interface
+   to an outgoing interface.  Without this no forwarding will take place from off box packets.
+
+.. option:: net.ipv6.conf.all_forwarding=1
+
+   This option allows the linux kernel to forward ipv6 packets incoming from one interface
+   to an outgoing interface.  Without this no forwarding will take place from off box packets.
+
+.. option:: net.ipv6.conf.all.keep_addr_on_down=1
+
+   When an interface is taken down, do not remove the v6 addresses associated with the interface.
+   This option is recommended because this is the default behavior for v4 as well.
+
+.. option:: net.ipv6.route.skip_notify_on_dev_down=1
+
+   When an interface is taken down, the linux kernel will not notify, via netlink, about routes
+   that used that interface being removed from the FIB.  This option is recommended because this
+   is the default behavior for v4 as well.
 
 Debugging
 =========