Types of Maps Overview

VPNv6 routes can be exported from the BGP RIB of an IPv6 VRF to the global IPv6 BGP RIB based on policy by means of a route map and the global export map command.

For example, if you have a mixed IPv4 and IPv6 VPN configuration, but want only the IPv6 VPN routes to be exported from the IPv6 VRF into the global IPv6 RIB, you can use a route map that matches on IPv6 access-lists (IPv6 prefix-lists). You can have the route map disallow IPv4 VPN routes by matching on IPv4 access lists that filter out IPv4 prefixes.

VPNv6 routes can be exported from the BGP RIB of an IPv6 VRF to the global IPv6 BGP RIB based on policy by means of a route map and the global export map command.

For example, if you have a mixed IPv4 and IPv6 VPN configuration, but want only the IPv6 VPN routes to be exported from the IPv6 VRF into the global IPv6 RIB, you can use a route map that matches on IPv6 access-lists (IPv6 prefix-lists). You can have the route map disallow IPv4 VPN routes by matching on IPv4 access lists that filter out IPv4 prefixes.

Export Maps

You can use an export map to change the attributes of a route when it is exported from a VRF to the global BGP VPN RIB local to the VR. This RIB is often referred to as the core VPN RIB. Export maps can optionally filter routes.

When the VRF route matches the export map, the route is exported and the attributes are changed as specified in the export map.

When the VRF route does not match the export map, the filter keyword determines what happens. If the filter keyword has been issued, then the route is not exported. If the filter keyword has not been issued, then the route is exported but the attributes of the route are not modified (because the export map was not matched).

If you do not configure an export map, then all routes are exported from the VRF to the global BGP VPN RIB. However, routes that are imported into the VRF cannot be exported again.

Global Export Maps

You can use a global export map to change the attributes of a route when it is exported from a VRF to the global BGP non-VPN RIB local to the VR.

If the VRF route matches the export map, then the route is exported and the attributes are changed as specified in the export map. If the VRF route does not match the export map, then the route is not exported. If you do not configure a global export map, then no routes are exported from the VRF to the global BGP non-VPN RIB.

Routes that are imported into the VRF cannot be exported again. As a consequence, VPN routes can be injected only into the global IP routing table on the PE router that is directly connected to the CE router that originates the prefix.

See Exporting IPv6 VPN Routes Globally into the Global BGP IPv6 RIB for information about global export maps and IPv6 VPNs.

Import Maps

You can use an import map to change the attributes of a route when it is imported from the global BGP VPN RIB to a VRF. You can also use an import map to filter routes. If you associate an import map with a VRF, that VRF then accepts only received routes that pass the import map (and match the import route target list).

Global Import Maps

Global import maps enable BGP routes to be imported from the global BGP non-VPN RIB into the BGP RIB of a VRF based on a configured route map. You can use import maps as an automated mechanism that enables a subset of the Internet to be reachable from a VPN. This feature is intended to provide simplified central access to a limited number of centralized services in the provider network. Use this feature to import only a relatively small number (tens) of routes from the global domain into the VPNs, such as a small number of routes to DNS servers, content servers, management stations, and so on.

If instead you import the full Internet routing table into one or more VPNs, too much memory will be consumed because this action stores multiple copies of the full Internet routing table. To prevent an accidental misconfiguration, you must specify the maximum number of routes to be imported into a VRF when you configure global import. If you must provide access to the full Internet from a VPN, use the fallback global command.

Use the max-routes keyword to specify the maximum number of routes that you want to be imported into the local RIB. BGP generates a log message when the specified number of routes has been imported; no additional routes are imported.

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