doc: Documentation update for ASBR Summarisation

This is for ASBR summarisation new feature addition.

Signed-off-by: Mobashshera Rasool <mrasool@vmware.com>

1 files changed, 77 insertions, 0 deletions

diff --git a/doc/user/ospf6d.rst b/doc/user/ospf6d.rst
index c4a1bc381..c26c69dd0 100644
--- a/doc/user/ospf6d.rst
+++ b/doc/user/ospf6d.rst
@@ -85,6 +85,83 @@ OSPF6 router
    change to take effect, user can use this cli instead of restarting the
    ospf6d daemon.
 
+ASBR Summarisation Support in OSPFv3
+====================================
+
+   External routes in OSPFv3 are carried by type 5/7 LSA (external LSAs).
+   External LSAs are generated by ASBR (Autonomous System Boundary Router).
+   Large topology database requires a large amount of router memory, which
+   slows down all processes, including SPF calculations.
+   It is necessary to reduce the size of the OSPFv3 topology database,
+   especially in a large network. Summarising routes keeps the routing
+   tables smaller and easier to troubleshoot.
+
+   External route summarization must be configured on ASBR.
+   Stub area do not allow ASBR because they don’t allow type 5 LSAs.
+
+   An ASBR will inject a summary route into the OSPFv3 domain.
+
+   Summary route will only be advertised if you have at least one subnet
+   that falls within the summary range.
+
+   Users will be allowed an option in the CLI to not advertise range of
+   ipv6 prefixes as well.
+
+   The configuration of ASBR Summarisation is supported using the CLI command
+
+.. clicmd:: summary-address X:X::X:X/M [tag (1-4294967295)] [{metric (0-16777215) | metric-type (1-2)}]
+
+   This command will advertise a single External LSA on behalf of all the
+   prefixes falling under this range configured by the CLI.
+   The user is allowed to configure tag, metric and metric-type as well.
+   By default, tag is not configured, default metric as 20 and metric-type
+   as type-2 gets advertised.
+   A summary route is created when one or more specific routes are learned and
+   removed when no more specific route exist.
+   The summary route is also installed in the local system with Null0 as
+   next-hop to avoid leaking traffic.
+
+.. clicmd:: no summary-address X:X::X:X/M [tag (1-4294967295)] [{metric (0-16777215) | metric-type (1-2)}]
+
+   This command can be used to remove the summarisation configuration.
+   This will flush the single External LSA if it was originated and advertise
+   the External LSAs for all the existing individual prefixes.
+
+.. clicmd:: summary-address X:X::X:X/M no-advertise
+
+   This command can be used when user do not want to advertise a certain
+   range of prefixes using the no-advertise option.
+   This command when configured will flush all the existing external LSAs
+   falling under this range.
+
+.. clicmd:: no summary-address X:X::X:X/M no-advertise
+
+   This command can be used to remove the previous configuration.
+   When configured, tt will resume originating external LSAs for all the prefixes
+   falling under the configured range.
+
+.. clicmd:: aggregation timer (5-1800)
+
+   The summarisation command takes effect after the aggregation timer expires.
+   By default the value of this timer is 5 seconds. User can modify the time
+   after which the external LSAs should get originated using this command.
+
+.. clicmd:: no aggregation timer (5-1800)
+
+   This command removes the timer configuration. It reverts back to default
+   5 second timer.
+
+.. clicmd:: show ipv6 ospf6 summary-address [detail] [json]
+
+   This command can be used to see all the summary-address related information.
+   When detail option is used, it shows all the prefixes falling under each
+   summary-configuration apart from other information.
+
+.. clicmd:: debug ospf6 lsa aggregation
+
+   This command can be used to enable the debugs related to the summarisation
+   of these LSAs.
+
 .. _ospf6-debugging:
 
 OSPFv3 Debugging