Configuration Guide

Table Of Contents
©2021 Extreme Networks, Inc. All rights reserved
October 2021
58
12. ISIS Accept Policy
Beginning in software release 4.1 for the VSP 4000/8000, 4.2.1 for the VSP 7200, and release 4.0 for the
VSP 9000, IS-IS accept policies for IPv4 is introduced. Prior to this release, the ISIS IPv4 routes received
over the SPB cloud are installed directly into the routing table. There is no ability to filter those routes and
apply incoming route policies to them. Hence, networks that are being migrated from other routing protocols
to ISIS/SPB are vulnerable to routing loops. ISIS accept policy functionality provides a way to avoid such
loops.
You can create an IS-IS accept policy for the Global Routing Table (GRT) or a Virtual Routing and
Forwarding (VRF) instance. You can create an IS-IS accept policy on a switch that operates at a global
default level or for a specific advertising BEB. You can also use the filter mechanism for ISIS accept policies
to redistribute routes between different VRFs, or between a VRF and the GRT.
ISIS policies can also use either a service instance identifier (ISID) or an ISID list to filter incoming traffic.
For inter-VRF route redistribution, an ISID value of 0 represents the GRT. For inter-VRF route redistribution
between VRFs, the ISID is the source VRF (or remote VRF).
You can filter traffic with ISIS accept policies by:
advertising BEB
ISID or ISID list (ISID take precedence over an ISID list)
route-map
You can use IS-IS accept policies to apply at a global default level for all advertising Backbone Edge Bridges
(BEBs) or for a specific advertising BEB.
IS-IS accept policies also allow you to use either a service instance identifier (ISID) or an ISID list to filter
routes. The switch uses ISIDs to define Virtual Services Networks (VSNs). ISIDs identify and transmit
virtualized traffic in an encapsulated SPBM frame. IS-IS accept policies can use ISIDs or ISID lists to filter
the incoming virtualized traffic.
IS-IS accept policies can also apply route policies to determine what incoming traffic to accept into the
routing table. With route policies the device can determine which routes to accept into the routing table
based on the criteria you configure, which can give precedence to advertised routes from a particular
protocol, route-source, route-type, or through other criteria.