saba8814 · Oct 7, 2026 · Oct 7, 2026 · Oct 7, 2026 · Oct 7, 2026 · troglobit
diff --git a/doc/ChangeLog.md b/doc/ChangeLog.md
@@ -14,6 +14,9 @@ All notable changes to the project are documented in this file.
   `ripng`/`ospfv3` type and the IPv6 address-family
 - Support building without Frr, which also drops bash.  The minimal
   defconfigs are now built this way, with static routing only, issue #1670
+- Configurable OSPF auto-cost reference bandwidth, for OSPFv2 and OSPFv3,
+  issue #1576.  The default, 100000 Mbit/s, is the value used before, so
+  link costs do not change on upgrade.  The CLI shows it in `show ip ospf`
 - Check for a new software release on demand: `upgrade` without a bundle in
   the CLI, the Check now button on the WebUI dashboard, or the `check-update`
   RPC, see [Unattended Software Updates][unattended]

diff --git a/doc/routing.md b/doc/routing.md
@@ -215,11 +215,13 @@ admin@example:/>
 ### OSPF global settings
 
 In addition to *area* and *interface* specific settings, OSPF provides
-global settings for route redistribution and OSPF router identifier.
+global settings for route redistribution, OSPF router identifier, and
+the reference bandwidth used to calculate interface costs.
 
 <pre class="cli"><code>admin@example:/config/> <b>edit routing control-plane-protocol ospfv2 name default ospf</b>
 admin@example:/config/routing/…/ospf/> <b>set ?</b>
   area                     List of OSPF areas.
+  auto-cost                Interface auto-cost configuration state.
   default-route-advertise  Distribute default route to network
   explicit-router-id       Defined in RFC 2328.  A 32-bit number
   redistribute             Redistribute protocols into OSPF
@@ -242,6 +244,24 @@ admin@example:/config/routing/…/ospf/> set
   router will distribute a default route even when it lacks a default
   route. The default route will be distributed as an *external type-2*
   (E2) route.
+- Reference bandwidth: Routers from different vendors only agree on
+  the shortest path if they use the same reference bandwidth.  The cost
+  of an interface without an explicit `cost` is the reference bandwidth
+  divided by the link speed, rounded, with 1 as the lowest cost.  The
+  default is 100000 Mbit/s, which gives a 1 Gbit/s link cost 100.  Use
+  `set auto-cost reference-bandwidth 10000` (Mbit/s) to change it.  A
+  link of unknown speed, e.g., a virtual link, counts as 10000 Mbit/s.
+  Auto-cost can not be disabled.
+
+`show ip ospf` shows the reference bandwidth in use, and `show ipv6
+ospf` does the same for OSPFv3.
+
+<pre class="cli"><code>admin@example:/> <b>show ip ospf</b>
+ OSPF Routing Process, Router ID: 192.168.10.1
+ Reference bandwidth: 100000 Mbit/s
+ Number of areas attached to this router: 1
+ ...
+</code></pre>
 
 
 ### Debug OSPFv2

diff --git a/src/confd/src/routing.c b/src/confd/src/routing.c
@@ -315,7 +315,7 @@ int parse_ospf_areas(sr_session_ctx_t *session, struct lyd_node *areas, FILE *fp
 int parse_ospf(sr_session_ctx_t *session, struct lyd_node *ospf)
 {
 	struct lyd_node *areas, *default_route, *debug;
-	const char *router_id;
+	const char *router_id, *refbw;
 	int bfd_enabled = 0;
 	int num_areas = 0;
 	FILE *fp;
@@ -381,6 +381,9 @@ int parse_ospf(sr_session_ctx_t *session, struct lyd_node *ospf)
 		}
 	}
 
+	refbw = lydx_get_cattr(lydx_get_child(ospf, "auto-cost"), "reference-bandwidth");
+	if (refbw)
+		fprintf(fp, "  auto-cost reference-bandwidth %s\n", refbw);
 	if (router_id)
 		fprintf(fp, "  ospf router-id %s\n", router_id);
 	fclose(fp);
@@ -429,7 +432,7 @@ static int parse_ospf6_areas(struct lyd_node *areas, FILE *fp)
 int parse_ospf6(sr_session_ctx_t *session, struct lyd_node *ospf)
 {
 	struct lyd_node *areas, *default_route, *debug;
-	const char *router_id;
+	const char *router_id, *refbw;
 	int bfd_enabled = 0;
 	int num_areas = 0;
 	FILE *fp;
@@ -489,6 +492,9 @@ int parse_ospf6(sr_session_ctx_t *session, struct lyd_node *ospf)
 		}
 	}
 
+	refbw = lydx_get_cattr(lydx_get_child(ospf, "auto-cost"), "reference-bandwidth");
+	if (refbw)
+		fprintf(fp, "  auto-cost reference-bandwidth %s\n", refbw);
 	if (router_id)
 		fprintf(fp, "  ospf6 router-id %s\n", router_id);
 	fclose(fp);

diff --git a/src/confd/yang/confd.inc b/src/confd/yang/confd.inc
@@ -14,7 +14,7 @@ MODULES=(
 	"ietf-routing@2018-03-13.yang"
 	"ietf-ipv6-unicast-routing@2018-03-13.yang"
 	"ietf-ipv4-unicast-routing@2018-03-13.yang"
-	"ietf-ospf@2022-10-19.yang -e bfd -e explicit-router-id -e hybrid-interface"
+	"ietf-ospf@2022-10-19.yang -e auto-cost -e bfd -e explicit-router-id -e hybrid-interface"
 	"ietf-rip@2020-02-20.yang"
 	"iana-bfd-types@2021-10-21.yang"
 	"ietf-bfd-types@2022-09-22.yang"
@@ -31,7 +31,7 @@ MODULES=(
 	"ieee802-dot1q-types@2022-10-29.yang"
 	"infix-ip@2026-04-28.yang"
 	"infix-if-type@2026-01-07.yang"
-	"infix-routing@2026-09-28.yang"
+	"infix-routing@2026-10-07.yang"
 	"ieee802-dot1ab-lldp@2022-03-15.yang"
 	"infix-lldp@2025-05-05.yang"
 	"infix-dhcp-common@2025-12-21.yang"

diff --git a/src/confd/yang/confd/infix-routing.yang b/src/confd/yang/confd/infix-routing.yang
@@ -26,12 +26,19 @@ module infix-routing {
   contact      "kernelkit@googlegroups.com";
   description  "Deviations and augments for ietf-routing, ietf-ospf, and ietf-rip.";
 
+  revision 2026-10-07 {
+    description "Add OSPF auto-cost reference-bandwidth, for OSPFv2 and
+                 OSPFv3.  The default 100000 Mbit/s matches the value
+                 previously used, and auto-cost can not be disabled.";
+    reference "internal";
+  }
+
   revision 2026-09-28 {
     description "Add ospf, rip, and bfd features, where ospf covers OSPFv2
                  and OSPFv3, and rip covers RIPv2 and RIPng.  A build without
                  FRR leaves them off, so only static routes can be configured
                  and the device advertises exactly what it supports.";
-    reference "Issue #1670";
+    reference "internal";
   }
 
   revision 2026-07-22 {
@@ -67,19 +74,19 @@ module infix-routing {
                  Allows displaying which area a route was learned from,
                  how long neighbors have been up, their DR/BDR role, and
                  the interface with local address.";
-    reference "Issue #1190";
+    reference "internal";
   }
 
   revision 2025-11-11 {
     description "Add BFD IP single-hop support (RFC 9127).
                  Deviate session-statistics (not implemented yet).";
-    reference "RFC 9127, Issue #1190";
+    reference "RFC 9127";
   }
   revision 2025-11-10 {
     description "Add must constraint to prevent backbone area as stub/NSSA.
                  Enable OSPF operational data for CLI: un-deviate priority,
                  hello-timer, wait-timer, route metric and route-tag fields.";
-    reference "RFC 2328, RFC 3101, Issue #1190";
+    reference "RFC 2328, RFC 3101";
   }
   revision 2024-11-27 {
     description "Deviate address-family in OSPF";
@@ -423,8 +430,21 @@ module infix-routing {
     }
   }
 
-  deviation "/rt:routing/rt:control-plane-protocols/rt:control-plane-protocol/ospf:ospf/ospf:auto-cost" {
-    deviate not-supported;
+  /* The reference bandwidth must be the same on all routers in the OSPF
+     domain.  Frr always derives the interface cost from it, unless a cost
+     is set on the interface, so auto-cost can not be disabled. */
+  deviation "/rt:routing/rt:control-plane-protocols/rt:control-plane-protocol/ospf:ospf/ospf:auto-cost/ospf:enabled" {
+    deviate add {
+      default "true";
+      must ". = 'true'" {
+        error-message "Disabling OSPF auto-cost is not supported.";
+      }
+    }
+  }
+  deviation "/rt:routing/rt:control-plane-protocols/rt:control-plane-protocol/ospf:ospf/ospf:auto-cost/ospf:reference-bandwidth" {
+    deviate add {
+      default "100000";
+    }
   }
   deviation "/rt:routing/rt:control-plane-protocols/rt:control-plane-protocol/ospf:ospf/ospf:database" {
     deviate not-supported;

diff --git a/.../yang/confd/infix-routing@2026-09-28.yang → .../yang/confd/infix-routing@2026-10-07.yang b/.../yang/confd/infix-routing@2026-09-28.yang → .../yang/confd/infix-routing@2026-10-07.yang
diff --git a/src/statd/python/cli_pretty/cli_pretty.py b/src/statd/python/cli_pretty/cli_pretty.py
@@ -5250,6 +5250,9 @@ def show_ospf(json_data):
 
     # OSPF Process header
     print(f" OSPF Routing Process, Router ID: {router_id}")
+    refbw = ospf.get('auto-cost', {}).get('reference-bandwidth')
+    if refbw is not None:
+        print(f" Reference bandwidth: {refbw} Mbit/s")
     print(f" Number of areas attached to this router: {len(areas)}")
     print()
 

diff --git a/src/statd/python/yanger/ietf_ospf.py b/src/statd/python/yanger/ietf_ospf.py
@@ -162,6 +162,27 @@ def add_routes(ospf, ipv6=False):
         insert(ospf, "ietf-ospf:local-rib", "ietf-ospf:route", routes)
 
 
+def add_auto_cost(ospf, daemon):
+    """Report the auto-cost reference bandwidth (Mbit/s) of an OSPF daemon.
+
+    Frr has no JSON for it, and its running-config only lists the value
+    when it differs from the default, 100000 Mbit/s in both ospfd and
+    ospf6d.  Auto-cost is always enabled in Frr."""
+    refbw = 100000
+
+    cmd = ("vtysh", "-c", f"show running-config {daemon}")
+    for line in HOST.run(cmd, default="").splitlines():
+        words = line.split()
+        if words[:2] == ["auto-cost", "reference-bandwidth"]:
+            refbw = int(words[2])
+            break
+
+    ospf["ietf-ospf:auto-cost"] = {
+        "enabled": True,
+        "reference-bandwidth": refbw,
+    }
+
+
 def add_areas(control_protocols):
     """Populate OSPF status"""
     cmd = ['/usr/libexec/statd/ospf-status']
@@ -308,6 +329,7 @@ def add_areas(control_protocols):
         area["ietf-ospf:interfaces"]["ietf-ospf:interface"] = interfaces
         areas.append(area)
 
+    add_auto_cost(control_protocol["ietf-ospf:ospf"], "ospfd")
     add_routes(control_protocol["ietf-ospf:ospf"])
     control_protocol["ietf-ospf:ospf"]["ietf-ospf:areas"]["ietf-ospf:area"] = areas
     insert(control_protocols, "control-plane-protocol", [control_protocol])
@@ -389,6 +411,7 @@ def add_areas6(control_protocols):
         area["ietf-ospf:interfaces"]["ietf-ospf:interface"] = interfaces
         areas.append(area)
 
+    add_auto_cost(control_protocol["ietf-ospf:ospf"], "ospf6d")
     add_routes(control_protocol["ietf-ospf:ospf"], ipv6=True)
     control_protocol["ietf-ospf:ospf"]["ietf-ospf:areas"]["ietf-ospf:area"] = areas
     insert(control_protocols, "control-plane-protocol", [control_protocol])

diff --git a/test/case/routing/Readme.adoc b/test/case/routing/Readme.adoc
@@ -10,6 +10,7 @@ Tests verifying standard routing protocols and configuration:
  - OSPF with BFD (Bidirectional Forwarding Detection)
  - OSPF default route advertisement and propagation
  - OSPF debug logging configuration and verification
+ - OSPF auto-cost reference bandwidth and interface cost
  - OSPF point-to-multipoint hybrid (broadcast) interface type
  - OSPF point-to-multipoint (non-broadcast) interface type with static neighbors
  - RIP basic neighbor discovery and route exchange
@@ -48,6 +49,10 @@ include::ospf_debug/Readme.adoc[]
 
 <<<
 
+include::ospf_auto_cost/Readme.adoc[]
+
+<<<
+
 include::ospf_point_to_multipoint_hybrid/Readme.adoc[]
 
 <<<

diff --git a/test/case/routing/all.yaml b/test/case/routing/all.yaml
@@ -29,6 +29,9 @@
 - name: OSPF Debug Logging
   case: ospf_debug/test.py
 
+- name: OSPF Auto-Cost Reference Bandwidth
+  suite: ospf_auto_cost/test.yaml
+
 - name: OSPF Point-to-Multipoint Hybrid
   suite: ospf_point_to_multipoint_hybrid/test.yaml
 

diff --git a/test/case/routing/ospf_auto_cost/Readme.adoc b/test/case/routing/ospf_auto_cost/Readme.adoc
@@ -0,0 +1,6 @@
+include::ospfv2.adoc[]
+
+<<<
+
+include::ospfv3.adoc[]
+
diff --git a/test/case/routing/ospf_auto_cost/ospfv2.adoc b/test/case/routing/ospf_auto_cost/ospfv2.adoc
@@ -0,0 +1,41 @@
+=== OSPFv2 Auto-Cost Reference Bandwidth
+
+ifdef::topdoc[:imagesdir: {topdoc}../../test/case/routing/ospf_auto_cost]
+
+==== Description
+
+Verifies that the OSPFv2 interface cost follows the configured auto-cost
+reference bandwidth.  The reference bandwidth must be the same on all
+routers in an OSPF domain, so it is changed on both R1 and R2.
+
+The cost of an interface is the reference bandwidth divided by the link
+speed, with 1 as the lowest cost.  A link of unknown speed, e.g., a virtual
+link, counts as 10000 Mbit/s.  On a 1 Gbit/s link the cost is:
+
+|===
+| Reference bandwidth      | Cost
+| 100000 Mbit/s (default)  | 100
+| 10000 Mbit/s             | 10
+| 1000 Mbit/s              | 1
+|===
+
+The test reads the link speed on each router to calculate the expected
+cost, and reads the reference bandwidth back from the operational
+datastore.
+
+==== Topology
+
+image::topology.svg[OSPFv2 Auto-Cost Reference Bandwidth topology, align=center, scaledwidth=75%]
+
+==== Sequence
+
+. Set up topology and attach to target DUTs
+. Configure OSPFv2 on R1 and R2
+. Wait for OSPFv2 adjacency between R1 and R2
+. Verify default reference bandwidth 100000 Mbit/s and link cost
+. Set reference bandwidth 10000 Mbit/s on R1 and R2
+. Verify reference bandwidth 10000 Mbit/s and link cost
+. Set reference bandwidth 1000 Mbit/s on R1 and R2
+. Verify reference bandwidth 1000 Mbit/s and link cost
+
+
diff --git a/test/case/routing/ospf_auto_cost/ospfv2.py b/test/case/routing/ospf_auto_cost/ospfv2.py
@@ -0,0 +1 @@
+test.py
diff --git a/test/case/routing/ospf_auto_cost/ospfv3.adoc b/test/case/routing/ospf_auto_cost/ospfv3.adoc
@@ -0,0 +1,41 @@
+=== OSPFv3 Auto-Cost Reference Bandwidth
+
+ifdef::topdoc[:imagesdir: {topdoc}../../test/case/routing/ospf_auto_cost]
+
+==== Description
+
+Verifies that the OSPFv3 interface cost follows the configured auto-cost
+reference bandwidth.  The reference bandwidth must be the same on all
+routers in an OSPF domain, so it is changed on both R1 and R2.
+
+The cost of an interface is the reference bandwidth divided by the link
+speed, with 1 as the lowest cost.  A link of unknown speed, e.g., a virtual
+link, counts as 10000 Mbit/s.  On a 1 Gbit/s link the cost is:
+
+|===
+| Reference bandwidth      | Cost
+| 100000 Mbit/s (default)  | 100
+| 10000 Mbit/s             | 10
+| 1000 Mbit/s              | 1
+|===
+
+The test reads the link speed on each router to calculate the expected
+cost, and reads the reference bandwidth back from the operational
+datastore.
+
+==== Topology
+
+image::topology.svg[OSPFv3 Auto-Cost Reference Bandwidth topology, align=center, scaledwidth=75%]
+
+==== Sequence
+
+. Set up topology and attach to target DUTs
+. Configure OSPFv3 on R1 and R2
+. Wait for OSPFv3 adjacency between R1 and R2
+. Verify default reference bandwidth 100000 Mbit/s and link cost
+. Set reference bandwidth 10000 Mbit/s on R1 and R2
+. Verify reference bandwidth 10000 Mbit/s and link cost
+. Set reference bandwidth 1000 Mbit/s on R1 and R2
+. Verify reference bandwidth 1000 Mbit/s and link cost
+
+
diff --git a/test/case/routing/ospf_auto_cost/ospfv3.py b/test/case/routing/ospf_auto_cost/ospfv3.py
@@ -0,0 +1 @@
+test.py