Juniper JUNOSE 11.2.X BGP AND MPLS, Руководство по настройке

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in the route map when the map returns an accept message. If the map returns a deny
message, then the route is not distributed.
Figure 91: Import and Export Maps
Both IPv4 and IPv6 VPNs are supported. You can specify that only IPv4 or only IPv6
routes are imported or exported. By default, the import or export map applies to both
kinds of routes. You can configure some maps to apply to IPv4 routes and different maps
to apply to IPv6 routes.
When the name or the contents of a route map change, BGP automatically waits for a
nonconfigurable hold-down interval of 30 seconds and then re-imports or re-exports
the appropriate routes using the modified route map.
Even when suppressed by an aggregate or auto-summary route, the more specific routes
are distributed. Aggregation and auto-summarization take place in each VRF
independently. For example, a route that is imported into a VRF is only aggregated in
that VRF if an aggregate address has been configured in the context of the BGP address
family for that VRF.
Routes maintain their type when exported. Private prefixes are exported without being
converted into public prefixes. Consequently the prefix of an exported route is the same
as the original route. Global export maps are therefore not useful when NAT is enabled.
Characteristics of Import and Global Import Maps
Import maps and global import maps can import both labeled and unlabeled routes. If
you want to import only one or the other, you can use a
match mpls-label command in
the global import route map. Furthermore, if BGP imports labeled routes from the global
BGP non-VPN RIB into a VRF RIB and then advertises them further upstream as labeled
routes, the MPLS cross-connects are correctly created and MPLS forwarding works. The
global VPN RIB never contains unlabeled routes, so the issue is moot for import maps.
When a route that was previously imported into the local VRF RIB is modified in the global
BGP RIB (VPN or non-VPN) such that it no longer matches the import or global import
map, that route is removed from the local VRF RIB.
429 Copyright © 2010, Juniper Networks, Inc.
Chapter 6: Configuring BGP-MPLS Applications