Managing L3 VPN virtual routing tables
A method of managing virtual routing forwarding (VRF) tables at a provider edge PE router of a L3 virtual private network (VPN) is provided. An import route target (ImpRT) tree is maintained at the PE router, which keeps the association between all ImpRT attributes currently configured on said PE router and the virtual routing table VRF at that router. When an ImpRT attribute is configured on a VRF table, the PE router first searches the tree to identify a local VRF table that contains a route(s) with that ImpRT attribute. If this information is available locally, the VRF is updated by copying the route information, and there is no need to do a route refresh. When an ImpRT is deleted from a VRF, a route refresh is avoided by parsing all the routes in the VRF and removing the routes that no longer have a matching route target. In an alternative implementation, the local source is the master RIB (routing information base) which includes all routes in all VRFs at the router, and optionally even rejected routes that were filtered out using ImpRTs. In this variant, even routes associated with ImpRTs that are new to the router would be available to update the VRF without requiring a route refresh.
1. A method of managing virtual routing forwarding (VRF) tables at a provider edge (PE) router of a L3 virtual private network (VPN), said PE router maintaining a VPN-IP master routing information base (RIB) and a sub-RIB for each said VRF table, comprising:
maintaining an import route target (ImpRT) tree comprising all ImpRT attributes currently configured on said PE router;
modifying an ImpRT attribute of a first VRF table in said PE router;
searching said ImpRT tree for a match to said modified ImpRT attribute to identify a second VRF table in said PE router having a matching ImpRT attribute;
for peers supporting a route refresh feature, performing a route refresh operation only when said match is not found;
for peers that do not support the route refresh feature, maintaining rejected routes in a rejected routes tree;
searching for routes in a sub-RIB associated with said second VRF table; and
copying said routes from said sub-RIB into said first VRF table based on all route target attributes configured for said first VRF table, including said modified ImpRT attribute.
2. The method of claim 1 , further comprising:
maintaining a list of all ImpRT attributes at a PE node with said ImpRT tree, each ImpRT attribute being associated with all VRF tables that are currently configured with said modified ImpRT attribute.
3. The method of claim 1 , further comprising:
adding said modified ImpRT attribute to said first VRF table.
4. The method of claim 3 , further comprising:
updating said ImpRT tree to include an association between said modified ImpRT attribute and said first VRF table.
5. The method of claim 1 , further comprising:
adding said routes to each VRF table in a routing database available at said PE router.
6. The method of claim 2 , wherein said searching is performed through said master RIB.
7. The method of claim 6 , wherein said master RIB includes all routes in all VRF tables at said PE router and further includes all routes that were filtered out at said PE router using ImpRT attributes.
8. The method of claim 1 , further comprising:
removing said ImpRT from said first VRF table.
9. The method of claim 8 , further comprising:
parsing all routes in said first VRF table and removing all routes from said first VRF table that no longer match said ImpRT of said first VRF table.
10. The method of claim 9 , further comprising:
deleting all routes that no longer match from the sub-RIB of said first VRF table.
11. The method of claim 10 , further comprising:
deleting in said master RIB every route that no longer matches any ImpRT attribute in said ImpRT tree.