veesix-networks · BSpendlove · Aug 28, 2026 · Aug 28, 2026 · Aug 28, 2026
diff --git a/docs/contributing/ci-and-review.md b/docs/contributing/ci-and-review.md
@@ -123,7 +123,7 @@ caused a real failure that took hours to attribute:
 
 ```yaml
 mgmt:
-  ipv4-subnet: 172.20.20.0/24
+  ipv4-subnet: ${OSVBNG_LAB_MGMT_PREFIX:=172.20}.20.0/24
 ```
 
 Without an explicit subnet, containerlab creates a dual-stack management
@@ -132,6 +132,17 @@ the route the test's own Router Advertisement installs. Subscriber
 originated IPv6 then leaves through management and dies, intermittently,
 in a way that looks like a dataplane bug.
 
+The /16 comes from `OSVBNG_LAB_MGMT_PREFIX` so a developer whose
+172.20.0.0/16 is already taken by another Docker network can run the
+suites on the shared `clab` network unchanged with, say,
+`OSVBNG_LAB_MGMT_PREFIX=172.31`. Suites with a private management
+network (`network: clab-NN`) stay on their literal 172.20 subnet: they
+pin each node's `mgmt-ipv4`, and their bind-mounted RADIUS, Kea and
+robot files name those addresses, which containerlab does not expand.
+Moving only the subnet puts a node outside its own network and the
+deploy hangs; such a suite runs elsewhere, or from a copy with every
+address rewritten.
+
 **Take the CPU slot from the environment.**
 
 ```yaml

diff --git a/tests/01-smoke/01-smoke.clab.yml b/tests/01-smoke/01-smoke.clab.yml
@@ -8,7 +8,7 @@ name: osvbng-smoke
 # dual-stack network whose static v6 default route on eth0 competes
 # with the test RA route and breaks subscriber-originated IPv6.
 mgmt:
-  ipv4-subnet: 172.20.20.0/24
+  ipv4-subnet: ${OSVBNG_LAB_MGMT_PREFIX:=172.20}.20.0/24
 
 topology:
   nodes:

diff --git a/tests/02-smoke-ha/02-smoke-ha.clab.yml b/tests/02-smoke-ha/02-smoke-ha.clab.yml
@@ -8,7 +8,7 @@ name: osvbng-smoke-ha
 # dual-stack network whose static v6 default route on eth0 competes
 # with the test RA route and breaks subscriber-originated IPv6.
 mgmt:
-  ipv4-subnet: 172.20.20.0/24
+  ipv4-subnet: ${OSVBNG_LAB_MGMT_PREFIX:=172.20}.20.0/24
 
 topology:
   nodes:

diff --git a/tests/03-ipoe-local/03-ipoe-local.clab.yml b/tests/03-ipoe-local/03-ipoe-local.clab.yml
@@ -8,7 +8,7 @@ name: osvbng-ipoe-local
 # dual-stack network whose static v6 default route on eth0 competes
 # with the test RA route and breaks subscriber-originated IPv6.
 mgmt:
-  ipv4-subnet: 172.20.20.0/24
+  ipv4-subnet: ${OSVBNG_LAB_MGMT_PREFIX:=172.20}.20.0/24
 
 topology:
   nodes:

diff --git a/tests/04-pppoe-local/04-pppoe-local.clab.yml b/tests/04-pppoe-local/04-pppoe-local.clab.yml
@@ -8,7 +8,7 @@ name: osvbng-pppoe-local
 # dual-stack network whose static v6 default route on eth0 competes
 # with the test RA route and breaks subscriber-originated IPv6.
 mgmt:
-  ipv4-subnet: 172.20.20.0/24
+  ipv4-subnet: ${OSVBNG_LAB_MGMT_PREFIX:=172.20}.20.0/24
 
 topology:
   nodes:

diff --git a/tests/08-cgnat-ipoe-pba/08-cgnat-ipoe-pba.clab.yml b/tests/08-cgnat-ipoe-pba/08-cgnat-ipoe-pba.clab.yml
@@ -8,7 +8,7 @@ name: osvbng-cgnat-ipoe-pba
 # dual-stack network whose static v6 default route on eth0 competes
 # with the test RA route and breaks subscriber-originated IPv6.
 mgmt:
-  ipv4-subnet: 172.20.20.0/24
+  ipv4-subnet: ${OSVBNG_LAB_MGMT_PREFIX:=172.20}.20.0/24
 
 topology:
   nodes:

diff --git a/tests/09-cgnat-ipoe-det/09-cgnat-ipoe-det.clab.yml b/tests/09-cgnat-ipoe-det/09-cgnat-ipoe-det.clab.yml
@@ -8,7 +8,7 @@ name: osvbng-cgnat-ipoe-det
 # dual-stack network whose static v6 default route on eth0 competes
 # with the test RA route and breaks subscriber-originated IPv6.
 mgmt:
-  ipv4-subnet: 172.20.20.0/24
+  ipv4-subnet: ${OSVBNG_LAB_MGMT_PREFIX:=172.20}.20.0/24
 
 topology:
   nodes:

diff --git a/tests/10-cgnat-pppoe-pba/10-cgnat-pppoe-pba.clab.yml b/tests/10-cgnat-pppoe-pba/10-cgnat-pppoe-pba.clab.yml
@@ -8,7 +8,7 @@ name: osvbng-cgnat-pppoe-pba
 # dual-stack network whose static v6 default route on eth0 competes
 # with the test RA route and breaks subscriber-originated IPv6.
 mgmt:
-  ipv4-subnet: 172.20.20.0/24
+  ipv4-subnet: ${OSVBNG_LAB_MGMT_PREFIX:=172.20}.20.0/24
 
 topology:
   nodes:

diff --git a/tests/11-cgnat-pppoe-det/11-cgnat-pppoe-det.clab.yml b/tests/11-cgnat-pppoe-det/11-cgnat-pppoe-det.clab.yml
@@ -8,7 +8,7 @@ name: osvbng-cgnat-pppoe-det
 # dual-stack network whose static v6 default route on eth0 competes
 # with the test RA route and breaks subscriber-originated IPv6.
 mgmt:
-  ipv4-subnet: 172.20.20.0/24
+  ipv4-subnet: ${OSVBNG_LAB_MGMT_PREFIX:=172.20}.20.0/24
 
 topology:
   nodes:

diff --git a/tests/12-cgnat-ha-ipoe-pba/12-cgnat-ha-ipoe-pba.clab.yml b/tests/12-cgnat-ha-ipoe-pba/12-cgnat-ha-ipoe-pba.clab.yml
@@ -8,7 +8,7 @@ name: osvbng-cgnat-ha-ipoe-pba
 # dual-stack network whose static v6 default route on eth0 competes
 # with the test RA route and breaks subscriber-originated IPv6.
 mgmt:
-  ipv4-subnet: 172.20.20.0/24
+  ipv4-subnet: ${OSVBNG_LAB_MGMT_PREFIX:=172.20}.20.0/24
 
 topology:
   nodes:

diff --git a/tests/13-cgnat-ha-pppoe-pba/13-cgnat-ha-pppoe-pba.clab.yml b/tests/13-cgnat-ha-pppoe-pba/13-cgnat-ha-pppoe-pba.clab.yml
@@ -8,7 +8,7 @@ name: osvbng-cgnat-ha-pppoe-pba
 # dual-stack network whose static v6 default route on eth0 competes
 # with the test RA route and breaks subscriber-originated IPv6.
 mgmt:
-  ipv4-subnet: 172.20.20.0/24
+  ipv4-subnet: ${OSVBNG_LAB_MGMT_PREFIX:=172.20}.20.0/24
 
 topology:
   nodes:

diff --git a/tests/14-ha-failover-ipoe/14-ha-failover-ipoe.clab.yml b/tests/14-ha-failover-ipoe/14-ha-failover-ipoe.clab.yml
@@ -8,7 +8,7 @@ name: osvbng-ha-failover-ipoe
 # dual-stack network whose static v6 default route on eth0 competes
 # with the test RA route and breaks subscriber-originated IPv6.
 mgmt:
-  ipv4-subnet: 172.20.20.0/24
+  ipv4-subnet: ${OSVBNG_LAB_MGMT_PREFIX:=172.20}.20.0/24
 
 topology:
   nodes:

diff --git a/tests/15-ha-failover-pppoe/15-ha-failover-pppoe.clab.yml b/tests/15-ha-failover-pppoe/15-ha-failover-pppoe.clab.yml
@@ -8,7 +8,7 @@ name: osvbng-ha-failover-pppoe
 # dual-stack network whose static v6 default route on eth0 competes
 # with the test RA route and breaks subscriber-originated IPv6.
 mgmt:
-  ipv4-subnet: 172.20.20.0/24
+  ipv4-subnet: ${OSVBNG_LAB_MGMT_PREFIX:=172.20}.20.0/24
 
 topology:
   nodes:

diff --git a/tests/16-ha-failover-radius-ipoe/16-ha-failover-radius-ipoe.clab.yml b/tests/16-ha-failover-radius-ipoe/16-ha-failover-radius-ipoe.clab.yml
@@ -8,7 +8,7 @@ name: osvbng-ha-failover-radius-ipoe
 # dual-stack network whose static v6 default route on eth0 competes
 # with the test RA route and breaks subscriber-originated IPv6.
 mgmt:
-  ipv4-subnet: 172.20.20.0/24
+  ipv4-subnet: ${OSVBNG_LAB_MGMT_PREFIX:=172.20}.20.0/24
 
 topology:
   nodes:

diff --git a/tests/17-ha-tracker-promotion-ipoe/17-ha-tracker-promotion-ipoe.clab.yml b/tests/17-ha-tracker-promotion-ipoe/17-ha-tracker-promotion-ipoe.clab.yml
@@ -8,7 +8,7 @@ name: osvbng-ha-tracker-promotion-ipoe
 # dual-stack network whose static v6 default route on eth0 competes
 # with the test RA route and breaks subscriber-originated IPv6.
 mgmt:
-  ipv4-subnet: 172.20.20.0/24
+  ipv4-subnet: ${OSVBNG_LAB_MGMT_PREFIX:=172.20}.20.0/24
 
 topology:
   nodes:

diff --git a/tests/18-ipoe-linux-client/18-ipoe-linux-client.clab.yml b/tests/18-ipoe-linux-client/18-ipoe-linux-client.clab.yml
@@ -8,7 +8,7 @@ name: osvbng-ipoe-linux-client
 # dual-stack network whose static v6 default route on eth0 competes
 # with the test RA route and breaks subscriber-originated IPv6.
 mgmt:
-  ipv4-subnet: 172.20.20.0/24
+  ipv4-subnet: ${OSVBNG_LAB_MGMT_PREFIX:=172.20}.20.0/24
 
 topology:
   nodes:

diff --git a/tests/19-ipoe-linux-client-cake/19-ipoe-linux-client-cake.clab.yml b/tests/19-ipoe-linux-client-cake/19-ipoe-linux-client-cake.clab.yml
@@ -8,7 +8,7 @@ name: osvbng-ipoe-linux-client-cake
 # dual-stack network whose static v6 default route on eth0 competes
 # with the test RA route and breaks subscriber-originated IPv6.
 mgmt:
-  ipv4-subnet: 172.20.20.0/24
+  ipv4-subnet: ${OSVBNG_LAB_MGMT_PREFIX:=172.20}.20.0/24
 
 topology:
   nodes:

diff --git a/tests/20-routing-policy/20-routing-policy.clab.yml b/tests/20-routing-policy/20-routing-policy.clab.yml
@@ -8,7 +8,7 @@ name: osvbng-routing-policy
 # dual-stack network whose static v6 default route on eth0 competes
 # with the test RA route and breaks subscriber-originated IPv6.
 mgmt:
-  ipv4-subnet: 172.20.20.0/24
+  ipv4-subnet: ${OSVBNG_LAB_MGMT_PREFIX:=172.20}.20.0/24
 
 topology:
   nodes:

diff --git a/tests/21-cli-openapi/21-cli-openapi.clab.yml b/tests/21-cli-openapi/21-cli-openapi.clab.yml
@@ -8,7 +8,7 @@ name: osvbng-cli-openapi
 # dual-stack network whose static v6 default route on eth0 competes
 # with the test RA route and breaks subscriber-originated IPv6.
 mgmt:
-  ipv4-subnet: 172.20.20.0/24
+  ipv4-subnet: ${OSVBNG_LAB_MGMT_PREFIX:=172.20}.20.0/24
 
 topology:
   nodes:

diff --git a/tests/22-mss-clamp/22-mss-clamp.clab.yml b/tests/22-mss-clamp/22-mss-clamp.clab.yml
@@ -8,7 +8,7 @@ name: osvbng-mss-clamp
 # dual-stack network whose static v6 default route on eth0 competes
 # with the test RA route and breaks subscriber-originated IPv6.
 mgmt:
-  ipv4-subnet: 172.20.20.0/24
+  ipv4-subnet: ${OSVBNG_LAB_MGMT_PREFIX:=172.20}.20.0/24
 
 topology:
   nodes:

diff --git a/tests/24-vrf-lite/24-vrf-lite.clab.yml b/tests/24-vrf-lite/24-vrf-lite.clab.yml
@@ -8,7 +8,7 @@ name: osvbng-vrf-lite
 # dual-stack network whose static v6 default route on eth0 competes
 # with the test RA route and breaks subscriber-originated IPv6.
 mgmt:
-  ipv4-subnet: 172.20.20.0/24
+  ipv4-subnet: ${OSVBNG_LAB_MGMT_PREFIX:=172.20}.20.0/24
 
 topology:
   nodes:

diff --git a/tests/25-l3vpn/25-l3vpn.clab.yml b/tests/25-l3vpn/25-l3vpn.clab.yml
@@ -8,7 +8,7 @@ name: osvbng-l3vpn
 # dual-stack network whose static v6 default route on eth0 competes
 # with the test RA route and breaks subscriber-originated IPv6.
 mgmt:
-  ipv4-subnet: 172.20.20.0/24
+  ipv4-subnet: ${OSVBNG_LAB_MGMT_PREFIX:=172.20}.20.0/24
 
 topology:
   nodes:

diff --git a/tests/26-dhcpv6-ldra/26-dhcpv6-ldra.clab.yml b/tests/26-dhcpv6-ldra/26-dhcpv6-ldra.clab.yml
@@ -8,7 +8,7 @@ name: osvbng-dhcpv6-ldra
 # dual-stack network whose static v6 default route on eth0 competes
 # with the test RA route and breaks subscriber-originated IPv6.
 mgmt:
-  ipv4-subnet: 172.20.20.0/24
+  ipv4-subnet: ${OSVBNG_LAB_MGMT_PREFIX:=172.20}.20.0/24
 
 topology:
   nodes:

diff --git a/tests/27-api-pagination/27-api-pagination.clab.yml b/tests/27-api-pagination/27-api-pagination.clab.yml
@@ -8,7 +8,7 @@ name: osvbng-api-pagination
 # dual-stack network whose static v6 default route on eth0 competes
 # with the test RA route and breaks subscriber-originated IPv6.
 mgmt:
-  ipv4-subnet: 172.20.20.0/24
+  ipv4-subnet: ${OSVBNG_LAB_MGMT_PREFIX:=172.20}.20.0/24
 
 topology:
   nodes:

diff --git a/tests/28-northbound-api-tls/28-northbound-api-tls.clab.yml b/tests/28-northbound-api-tls/28-northbound-api-tls.clab.yml
@@ -8,7 +8,7 @@ name: osvbng-northbound-api-tls
 # dual-stack network whose static v6 default route on eth0 competes
 # with the test RA route and breaks subscriber-originated IPv6.
 mgmt:
-  ipv4-subnet: 172.20.20.0/24
+  ipv4-subnet: ${OSVBNG_LAB_MGMT_PREFIX:=172.20}.20.0/24
 
 topology:
   nodes:

diff --git a/tests/30-l2tp-lns/30-l2tp-lns.clab.yml b/tests/30-l2tp-lns/30-l2tp-lns.clab.yml
@@ -8,7 +8,7 @@ name: osvbng-l2tp-lns
 # dual-stack network whose static v6 default route on eth0 competes
 # with the test RA route and breaks subscriber-originated IPv6.
 mgmt:
-  ipv4-subnet: 172.20.20.0/24
+  ipv4-subnet: ${OSVBNG_LAB_MGMT_PREFIX:=172.20}.20.0/24
 
 topology:
   nodes:

diff --git a/tests/31-l2tp-lac/31-l2tp-lac.clab.yml b/tests/31-l2tp-lac/31-l2tp-lac.clab.yml
@@ -8,7 +8,7 @@ name: osvbng-l2tp-lac
 # dual-stack network whose static v6 default route on eth0 competes
 # with the test RA route and breaks subscriber-originated IPv6.
 mgmt:
-  ipv4-subnet: 172.20.20.0/24
+  ipv4-subnet: ${OSVBNG_LAB_MGMT_PREFIX:=172.20}.20.0/24
 
 topology:
   nodes:

diff --git a/tests/32-ipoe-opdb-restore/32-ipoe-opdb-restore.clab.yml b/tests/32-ipoe-opdb-restore/32-ipoe-opdb-restore.clab.yml
@@ -8,7 +8,7 @@ name: osvbng-ipoe-opdb-restore
 # dual-stack network whose static v6 default route on eth0 competes
 # with the test RA route and breaks subscriber-originated IPv6.
 mgmt:
-  ipv4-subnet: 172.20.20.0/24
+  ipv4-subnet: ${OSVBNG_LAB_MGMT_PREFIX:=172.20}.20.0/24
 
 topology:
   nodes:

diff --git a/tests/33-pppoe-opdb-restore/33-pppoe-opdb-restore.clab.yml b/tests/33-pppoe-opdb-restore/33-pppoe-opdb-restore.clab.yml
@@ -8,7 +8,7 @@ name: osvbng-pppoe-opdb-restore
 # dual-stack network whose static v6 default route on eth0 competes
 # with the test RA route and breaks subscriber-originated IPv6.
 mgmt:
-  ipv4-subnet: 172.20.20.0/24
+  ipv4-subnet: ${OSVBNG_LAB_MGMT_PREFIX:=172.20}.20.0/24
 
 topology:
   nodes:

diff --git a/tests/34-cgnat-restart-idempotent/34-cgnat-restart-idempotent.clab.yml b/tests/34-cgnat-restart-idempotent/34-cgnat-restart-idempotent.clab.yml
@@ -8,7 +8,7 @@ name: osvbng-cgnat-restart-idempotent
 # dual-stack network whose static v6 default route on eth0 competes
 # with the test RA route and breaks subscriber-originated IPv6.
 mgmt:
-  ipv4-subnet: 172.20.20.0/24
+  ipv4-subnet: ${OSVBNG_LAB_MGMT_PREFIX:=172.20}.20.0/24
 
 topology:
   nodes:

diff --git a/tests/35-ipoe-family-disabled/35-ipoe-family-disabled.clab.yml b/tests/35-ipoe-family-disabled/35-ipoe-family-disabled.clab.yml
@@ -8,7 +8,7 @@ name: osvbng-ipoe-family-disabled
 # dual-stack network whose static v6 default route on eth0 competes
 # with the test RA route and breaks subscriber-originated IPv6.
 mgmt:
-  ipv4-subnet: 172.20.20.0/24
+  ipv4-subnet: ${OSVBNG_LAB_MGMT_PREFIX:=172.20}.20.0/24
 
 topology:
   nodes:

diff --git a/tests/37-ha-graceful-switchover-ipoe/37-ha-graceful-switchover-ipoe.clab.yml b/tests/37-ha-graceful-switchover-ipoe/37-ha-graceful-switchover-ipoe.clab.yml
@@ -8,7 +8,7 @@ name: osvbng-ha-graceful-ipoe
 # dual-stack network whose static v6 default route on eth0 competes
 # with the test RA route and breaks subscriber-originated IPv6.
 mgmt:
-  ipv4-subnet: 172.20.20.0/24
+  ipv4-subnet: ${OSVBNG_LAB_MGMT_PREFIX:=172.20}.20.0/24
 
 topology:
   nodes:

diff --git a/tests/51-ipoe-hqos-svlan/51-ipoe-hqos-svlan.clab.yml b/tests/51-ipoe-hqos-svlan/51-ipoe-hqos-svlan.clab.yml
@@ -8,7 +8,7 @@ name: osvbng-ipoe-hqos-svlan
 # dual-stack network whose static v6 default route on eth0 competes
 # with the test RA route and breaks subscriber-originated IPv6.
 mgmt:
-  ipv4-subnet: 172.20.20.0/24
+  ipv4-subnet: ${OSVBNG_LAB_MGMT_PREFIX:=172.20}.20.0/24
 
 topology:
   nodes:

diff --git a/tests/52-pppoe-hqos-svlan/52-pppoe-hqos-svlan.clab.yml b/tests/52-pppoe-hqos-svlan/52-pppoe-hqos-svlan.clab.yml
@@ -8,7 +8,7 @@ name: osvbng-pppoe-hqos-svlan
 # dual-stack network whose static v6 default route on eth0 competes
 # with the test RA route and breaks subscriber-originated IPv6.
 mgmt:
-  ipv4-subnet: 172.20.20.0/24
+  ipv4-subnet: ${OSVBNG_LAB_MGMT_PREFIX:=172.20}.20.0/24
 
 topology:
   nodes:

diff --git a/tests/common.robot b/tests/common.robot
@@ -11,8 +11,13 @@ Library             Collections
 *** Variables ***
 # preserve-env carries the CI runner's per-slot core assignment through
 # sudo so containerlab can expand it in the topologies; unset locally,
-# where the ${VAR:=auto} defaults select the auto layout.
-${CLAB_BIN}             sudo --preserve-env=OSVBNG_LAB_WORKER_CORES,OSVBNG_LAB_CP_CORES containerlab
+# where the ${VAR:=auto} defaults select the auto layout. The management
+# prefix rides the same way: topologies on the shared clab network sit
+# under ${OSVBNG_LAB_MGMT_PREFIX:=172.20}, so a box where 172.20.0.0/16
+# is taken by another Docker network runs those suites with the prefix
+# moved, not with edited topologies. Suites with a private management
+# network pin node addresses in bind-mounted configs and keep 172.20.
+${CLAB_BIN}             sudo --preserve-env=OSVBNG_LAB_WORKER_CORES,OSVBNG_LAB_CP_CORES,OSVBNG_LAB_MGMT_PREFIX containerlab
 ${runtime}              docker
 ${OSVBNG_API_PORT}      8080
 # 300 x 1s keeps the same 5-minute budget as the previous 60 x 5s but