This document goes through the steps to configure Campus Fabric IP Clos using Mist Campus Fabric Wizard.

Campus Fabric Configuration Best Practices

• Configure VLANs at switch template level and import them while configuring campus fabric. Template must be the single source of truth for all VLANs and port profiles unless specifically required at the switch or site level.
• At the access layer, avoid using trunk port profiles that allow all VLANs, unless explicitly required.
• Create VRF and VRF network configuration via the campus fabric, not via switch templates.
• Create port assignments per role and overwrite the configuration on individual device as needed.
• Manage the DHCP relay configuration via the campus fabric workflow, except for the service block devices.

Note: In topologies that are built in Mist cloud after the May 2025 updates, Mist automatically detects and reports any EVPN loops and duplicate MAC addresses. These issues are displayed on the switch Insights page.EVPN loop detection—EVPN-VXLAN lightweight PE-CE loop detection helps in detecting and breaking LAN Ethernet loops on downstream leaf-to-server or access ports. This feature can detect loops caused by issues such as miswired fabric components or third-party switches incorrectly connected to the fabric.For this feature to work, the switch must run the Junos OS version 24.4R1 or later. For more information, refer to EVPN-VXLAN Lightweight Leaf to Server Loop Detection.

• Duplicate MAC address detection—Identifies and mitigates issues arising from MAC address movement (MAC mobility) between different interfaces or devices in EVPN environments. While some MAC mobility is expected (for example, when a device actually moves), rapid changes might indicate issues such as network loops or misconfigurations. For more information, refer to Configuring Loop Detection for Duplicate MAC Addresses.

To configure campus fabric IP Clos:

1. Click Organization > Campus Fabric.
2. If you want to create the campus fabric for a site, select the site from the drop-down list beside the page heading. If you want to create the campus fabric for the entire organization, select Entire Org from the drop-down list.

You can use an organization-level campus fabric topology to build a campus-wide architecture with multiple buildings. Otherwise, build a site-specific campus fabric with a single set of core, distribution, and access switches.

3.Click whichever option is relevant. Click the:

• Configure Campus Fabric button (displayed if the site doesn't have a campus fabric configuration associated with it).
• Create Campus Fabric button (displayed if the site already has at least one campus fabric configuration associated with it).

The Topology tab is displayed.

4.Select the topology type Campus Fabric IP Clos.

5.Configure the topology name and other settings on the Topology tab, as described below:

NOTE: We recommend that you use the default settings on this screen unless they conflict with any networks attached to the campus fabric. The point-to-point links between each layer utilize /31 addressing to conserve addresses.

a. In the CONFIGURATION section, enter the following:

• Topology Name—Enter a name for the topology.

b. (If you don't want to use the default settings) In the TOPOLOGY SETTINGS section, enter the following:

• BGP Local AS—Represents the starting point of private BGP AS numbers that are automatically allocated to each device. You can use any private BGP AS number range that suits your deployment. Mist provisions the routing policy so that only the loopback IP addresses are exchanged in the underlay of the fabric.
• Underlay—Select an internet protocol version for the underlay. Options are IPv4 and IPv6.
• Subnet— The range of IP addresses that Mist uses for point-to-point links between devices. You can use a range that suits your deployment. Mist breaks this subnet into /31 subnet addressing per link. You can modify this number to suit the specific deployment scale. For example, a /24 network would provide up to 128 point-to-point /31 subnets.
• IPv6 Loopback Interface—Specify an IPv6 loopback interface subnet, which is used to autoconfigure IPv6 loopback interface on each device in the fabric.
• IPv4 Auto Router ID Subnet / Loopback Interface—Mist uses this subnet to automatically assign a router ID to each device in the fabric (including access devices irrespective of whether they are configured with EVPN or not). Router IDs are loopback interfaces (lo0.0) used for overlay peering between devices. For new topologies, this field auto-populates a default subnet value (172.16.254.0/23), which you can modify. When you edit an existing topology, this field doesn’t populate a default value. A router ID is used as an identifier when deploying routing protocols such as BGP.
• For IPv4 deployments, you have an option to disable automatic router ID assignment and configure router IDs manually. To do that, leave this field blank and then manually configure router IDs from the Nodes tab.
  • For IPv4 deployments, you can also overwrite the automatically assigned router ID by manually configuring a loopback interface in the Router ID field on the Routing tile on the switch configuration page (Switches > Switch Name). However, if you subsequently modify the campus fabric configuration, Mist performs automatic assignment of the router ID again, replacing the manually configured loopback interface.
  • Loopback per-VRF subnet—Mist uses this subnet to automatically configure loopback interfaces (lo0.x) per virtual routing and forwarding (VRF) instance that is used for services such as DHCP relay. For new topologies, this field auto-populates a default subnet value (172.16.192.0/24), which you can modify. This field supports a /19 or smaller subnet (for example, /24). When you edit an existing topology, this field doesn’t populate a default value.

When you define a Loopback Per-VRF IPv4 or IPv6 subnet, Mist automatically creates a corresponding aggregate route for the entire subnet (applicable to EX and QFX Series switches). You can override this configuration at the VRF level from the Network Settings tab.

6.Click Continue to go to the Nodes tab, where you can select devices that form part of the campus fabric IP Clos deployment.

7.Add switches to the Core, Distribution, and Access layer sections as required.To add the switches:

a. Click Select Switches in the section to which you want to add switches.

b. Select the switches that you want to add to the campus fabric.

c. Click Select.

We recommend that you validate the presence of each device in the switch inventory before creating the campus fabric.

By default, Mist configures the core switches to function as border nodes that run the services block functionality. In a campus fabric topology, border nodes interconnect external devices such as firewalls, routers, or critical devices. External services or devices (for example, DHCP and RADIUS servers) connect to the campus fabric through border nodes. If you want to offload this task from the core switches and use dedicated switches as border nodes, clear the Use Core as border checkbox on the upper left of the page. You can then add up to two switches as dedicated border nodes. The minimum number of dedicated border nodes required is one.

Also, Mist provides pods for improved scalability. Your access and distribution devices are grouped into pods. A pod could represent a building. For example, you can create a pod for each of the buildings in your site and create connections between the access and the distribution devices in that pod. You do not have to connect the same set of access devices to the distribution devices across multiple buildings. You can create multiple pods by clicking +Add Nodes.

You need only one connection between a pod and the core switch. You do not have to connect each distribution switch in a pod to all the core switches used. In an IPClos topology, you need only one connection between each core and distribution pair and between each distribution and access pair.

Note: If you leave the Auto Router ID Subnet / Loopback Interface field on the Topology tab blank, you must configure router IDs for the switches manually. To do so, select a switch that you added to the fabric and configure the router ID in the pane that appears on the right. Manual router ID assignment is supported only for IPv4 deployments.

8.After selecting the switches, click Continue to go to the Network Settings tab, where you can configure the networks.

9.Configure the network settings, as described below.

a. From the NETWORKS tile, add networks or VLANs to the configuration. You can either create a new network or import the network from the switch template defined in the Organization > Switch templates page.

To add a new VLAN, click Create New Network and configure the VLANs. The settings include a name, VLAN ID, and a subnet. You can specify IPv4 or IPv6 addresses for the subnet.

You can optionally configure IPv4 and IPv6 Anycast Gateway addresses in addition to any IPv4 or IPv6 subnets you have configured. The Mist UI uses those gateways as the Anycast IP address assignment across all Access and Distribution switches in the Campus Fabric configuration.

NOTE: If the Anycast Gateway fields are left empty, the Mist UI uses the existing logic, which is to use the first IP address in the subnet as the Anycast address.

To import VLANs from the template:

1. Click Add Existing Network.
2. Select a switch template from the Template drop-down list to view the VLANs available in that template.
3. Select the required VLAN from the displayed list, and click the ✓ mark.

VLANs are mapped to Virtual Network Identifiers (VNIs). You can optionally map the VLANs to VRF instances to logically separate the traffic.

b. Review the settings on the OTHER IP CONFIGURATION tile. This tile populates the settings automatically after you specify the networks in the NETWORKS section.

Mist provides automatic IP addressing of IRB for each of the VLANs. Then, the port profile associates the VLAN with the specified ports.

c. Optionally, configure VRF instances. Mist recommends using VRFs in network segments where traffic isolation and overlapping IP address spaces are required. By default, Mist places all VLANs in the default VRF. The VRF option allows you to group common VLANs into the same VRF or separate VRFs depending on traffic isolation requirements. All VLANs within each VRF have full connectivity with each other and with other external networking resources. A common use case is the isolation of guest wireless traffic from most enterprise domains except Internet connectivity. By default, a campus fabric provides complete isolation between VRFs, forcing inter-VRF communications to traverse a firewall. If you require inter-VRF communication, you need to include extra routes to the VRF. The extra route could be a default route that instructs the campus fabric to use an external router. It could also be a firewall for further security inspection or routing capabilities.

To create a VRF:

i. On the VRF tile, click Add VRF Instance and specify the settings. The settings include the following:

• Name for the VRF
• The networks to be associated with the VRF
• Loopback Per-VRF IPv4 Subnet and Loopback Per-VRF IPv4 Subnet—Mist uses this subnet to automatically configure loopback interfaces (lo0.x) per VRF instance that is used for services such as DHCP relay. Mist automatically creates an aggregate route for the Loopback Per-VRF IPv4 or IPv6 subnet defined (applicable to EX and QFX Series switches). This setting overrides the Loopback Per-VRF IPv4 or IPv6 Subnet defined on the Topology tab.

ii. To add extra routes, click the Add Extra Routes link on the New VRF Instance page and specify static or aggregate routes. Click the Add Static Route link on the Static Routes tab to configure static routes. Similarly, click the Add Aggregate Route link on the Aggregate Routes tab to configure aggregate routes (applicable to EX and QFX Series switches). You can specify IPv4 or IPv6 addresses for these routes. Aggregate routes are used to summarize internal fabric routes for advertisement to external peers like firewalls or WAN routers and are pushed only to the devices defined as border nodes or core nodes (if the fabric has no border node). To configure aggregate routes, specify the following:

• Destination—The aggregate route prefix in CIDR notation. Both IPv4 (for example, 192.168.0.0/16) and IPv6 (for example, 2001:db8::/32) prefixes are supported.
• Metric (Optional)—The routing metric assigned to the aggregate route, used for route selection. Valid range: 0–4,294,967,295.
• Preference (Optional)—The route preference (administrative distance) assigned to the aggregate route. A lower value indicates higher preference. The default preference for aggregate routes in Junos OS is 130. Valid range: 0–4,294,967,295.
• Discard (Optional)—Enabled by default. When enabled, packets matching the aggregate prefix but not matching any more-specific contributing route are silently dropped. This prevents routing loops and is the recommended configuration.

d. On the DHCP RELAY tile, configure the DHCP relay settings. You have the following options:

• Enabled—Configures DHCP relay on all the IRB-enabled devices in campus fabric. This option allows you to enable DHCP Relay on networks that you selected. The network will be populated inside the DHCP Relay tile as long as it is listed on the Networks tab on the same page.
• Disabled—Disable DHCP relay on the devices in campus fabric. When you select this option, the DHCP relay is disabled on all the IRB-enabled devices. You should carefully select this option as this will remove the locally defined DHCP Relay on the Switch Detail page.
• None—This option is automatically selected when the campus fabric topology has a mix of devices in terms of the DHCP relay configuration; that is, some devices have the DHCP relay enabled, some have it disabled, and some do not have it defined.

If you want to remove all locally defined DHCP Relay networks, select Enabled and then choose Remove all existing device level DHCP Networks. You can simplify your DHCP Relay deployment by centralizing any configuration change from the campus fabric workflow.

If you enable DHCP relay in a campus fabric configuration, it is enabled on all the IRB-defined devices in the fabric and disabled on the rest of the devices. For example, in Campus Fabric IP Clos edge topologies, DHCP is enabled on access devices and disabled on the rest.

10.Click Continue to go to the Ports tab, where you can configure the ports and create a connection between the core, distribution, and access layer switches.

11.Configure the switch ports in the core layer as described below:Select a switch in the Core section to open the switch port panel.

a. From the port panel of the core switch, select a port that you want to configure.

b. Specify a port type (for example, ge or xe).

c. Choose the distribution switch on which the link should terminate. You need to configure all the ports that need to be part of the campus fabric.

To configure switch ports in the distribution layer:

a. Select a switch in the Distribution section to open the switch port panel.

b. From the port panel of the switch, select a port that you want to configure.

c. Specify a port type (example: ge or xe).

d. Select:

• Link to Core to connect the port to a core switch.
• Link to Access to connect the port to an access switch.

e. Select the core or access switch (based on the selection in the previous step) on which the link should terminate. You need to configure all the ports that need to be part of the campus fabric.

To configure switch ports in the access layer:

1. Select a switch in the Access section to open the switch port panel.
2. From the port panel of the switch, select a port that you want to configure.
3. Specify a port type (example: ge and xe).
4. Choose the distribution switch on which the link should terminate. You need to configure all the ports that need to be part of the campus fabric.

If you want to view the configuration and status information of a specific port, hover over the numbered box representing that port in the port panel UI.

12.Click Continue to go to the Confirmation tab.

13.Click each switch icon to view and verify the configuration.

14.After verifying the configuration, click Apply Changes > Confirm.

The campus fabric configuration is saved to the Mist cloud. The configuration is immediately applied to the switches if they are online. If the switches are offline, the configuration will be applied to them when they come online next time. A switch might take up to 10 minutes to complete the configuration.

15.Click Close Campus Fabric Configuration.

Once the campus fabric is built or is in the process of being built, you can download the connection table, which represents the physical layout of the campus fabric. You can use this table to validate all switch interconnects for the devices participating in the physical campus fabric build. Click Connection Table to download it (.csv format).

16.Verify the campus fabric configuration. To verify, follow the steps listed in the Verification section of Campus Fabric IP Clos Wired Assurance.

For more detailed information about IP Clos architecture and its deployment, see Campus Fabric IP Clos Using Mist Wired Assurance—Juniper Validated Design (JVD).