From 4907bcd8a58dec95552875dac3c05a7014d43771 Mon Sep 17 00:00:00 2001 From: bisdhdh Date: Fri, 18 Dec 2020 03:27:45 +0530 Subject: [PATCH] doc: Add BGP GR command for preserving forwarding state. BGP GR command for preserving forwarding state command is Added to the docs. Signed-off-by: Biswajit Sadhu --- doc/user/bgp.rst | 32 ++++++++++++++++++++++++++++++++ 1 file changed, 32 insertions(+) diff --git a/doc/user/bgp.rst b/doc/user/bgp.rst index c65f1144eb..9483c86510 100644 --- a/doc/user/bgp.rst +++ b/doc/user/bgp.rst @@ -798,6 +798,38 @@ The following functionality is provided by graceful restart: <---------------------------------------------------------------------> +.. _bgp-GR-preserve-forwarding-state: + +BGP-GR Preserve-Forwarding State +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +BGP OPEN message carrying optional capabilities for Graceful Restart has +8 bit “Flags for Address Family” for given AFI and SAFI. This field contains +bit flags relating to routes that were advertised with the given AFI and SAFI. + +.. code-block:: frr + + 0 1 2 3 4 5 6 7 + +-+-+-+-+-+-+-+-+ + |F| Reserved | + +-+-+-+-+-+-+-+-+ + +The most significant bit is defined as the Forwarding State (F) bit, which +can be used to indicate whether the forwarding state for routes that were +advertised with the given AFI and SAFI has indeed been preserved during the +previous BGP restart. When set (value 1), the bit indicates that the +forwarding state has been preserved. +The remaining bits are reserved and MUST be set to zero by the sender and +ignored by the receiver. + +.. index:: bgp graceful-restart preserve-fw-state +.. clicmd:: bgp graceful-restart preserve-fw-state + +FRR gives us the option to enable/disable the "F" flag using this specific +vty command. However, it doesn't have the option to enable/disable +this flag only for specific AFI/SAFI i.e. when this command is used, it +applied to all the supported AFI/SAFI combinations for this peer. + .. _bgp-end-of-rib-message: End-of-RIB (EOR) message -- 2.39.5