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Virtual Network Policy

Virtual Network Policy Overview

Virtual network policies include the following details:

Policy Details Description
IP Links to Generic Systems MTU

Specifies the MTU for all L3 IP links facing generic system. A null or empty (default) value implies that any MTU will not be explicitly rendered; the device default MTU is used. Custom larger MTU may be required to provide EVPN DCI functionality or to support fabric wide Jumbo frame functionality. For EVPN-DCI, we recommend an MTU of 9050.

Max External Routes Count

Maximum number of routes to accept from external routers. The default (None) does not render any maximum-route commands on BGP sessions, implying that vendor defaults are used. An integer between range 1 to 2**32-1 sets a maximum limit of routes in BGP config. The value 0 (zero) intends the device to never apply a limit to number of EVPN routes (effectively unlimited). We suggest that this value is effectively unlimited on EVPN blueprints, to permit the high number of /32 and /128 routes to be advertised and received between VRFs in the event an external router is providing a form of route leaking functionality.

Max MLAG Routes Count

Maximum number of routes to accept across MLAG peer switches. The default (None) does not render any maximum-route commands on BGP sessions, implying that vendor defaults are used. An integer between range 1 to 2**32-1 sets a maximum limit of routes in BGP config. The value 0 (zero) intends the device to never apply a limit to number down BGP sessions if maximums are exceeded on a session. For EVPN blueprints, this should be combined with max_evpn_routes to permit routes across the L3 peer link which may contain many /32 and /128 from EVPN type-2 routes that convert into BGP route advertisements.

Max EVPN Routes Count

Maximum number of EVPN routes to accept on an EVPN switch. The default (None) does not render any maximum-route commands on BGP sessions, implying that vendor defaults are used. An integer between range 1 to 2**32-1 sets a maximum limit of routes in BGP config. The value 0 (zero) intends the device to never apply a limit to number of EVPN routes (effectively unlimited). Note: Device vendors typically shut down BGP sessions if maximums are exceeded on a session.

Max Fabric Routes Count

Maximum number of routes to accept between spine and leaf in the fabric, and spine-superspine. This includes the default VRF. You may need to set this option in the event of leaking EVPN routes from a routing zone into the default routing zone (VRF) which could generate a large number of /32 and /128 routes. We suggest that this value is effectively unlimited on all blueprints to ensure the network stability of spine-leaf BGP sessions and EVPN underlay. We also suggest unlimited for non-EVPN blueprints considering the impact to traffic if spine-leaf sessions go offline. An integer between 1-2**32-1 will set a maximum limit of routes in BGP config. The value 0 (zero) intends the device to never apply a limit to number of fabric routes (effectively unlimited).

EVPN Type 5 Routes

Default disabled. When enabled all EVPN vteps in the fabric redistribute ARP/IPV6 ND (when possible on NOS type) as EVPN type 5 /32 routes in the routing table. Currently, this option is certified for Juniper Junos only. FRR (SONiC/Cumulus) does this implicitly and cannot be disabled. This setting results in a blueprint warning that it is not supported. This value is disabled by default, as it generates a very large number of routes in the BGP routing table and takes large amounts of TCAM allocation space. When these /32 and /128 routes are generated, it assists in direct unicast routing to host destinations on VNIs that are not stretched to the ingress vtep, and avoids a route lookup to a subnet (such as /24) that may be hosted on many leafs. The directed host route prevents a double lookup to one of many vteps may hosts the /24 and instead routes the destination directly to the correct vtep.

Generate EVPN host routes from ARP/IPV6 ND ARP

Setting "Generate EVPN host routes from ARP/IPV6 ND ARP" adds a policy-statement to the export policy used within the fabric.

Modify Virtual Network Policy

  1. From the blueprint, navigate to Staged > Policies > Virtual Network Policy and click Modify Settings (right side).
  2. Make your changes.
  3. Click Save Changes.