As we said when we described the functions of a route server (see Description of the Route Server model), it is in charge of all the route filtering. To achieve that, the In and Out filters from the RA, RB and RC configurations must be converted into Import and Export policies in the route server.
This is a fragment of the route server configuration (we only show the policies for client RA):
# Configuration for Route Server ('RS') ! hostname RS password ix ! bgp multiple-instance ! router bgp 65000 view RS no bgp default ipv4-unicast neighbor 2001:0DB8::A remote-as 65001 neighbor 2001:0DB8::B remote-as 65002 neighbor 2001:0DB8::C remote-as 65003 ! address-family ipv6 neighbor 2001:0DB8::A activate neighbor 2001:0DB8::A route-server-client neighbor 2001:0DB8::A route-map RSCLIENT-A-IMPORT import neighbor 2001:0DB8::A route-map RSCLIENT-A-EXPORT export neighbor 2001:0DB8::A soft-reconfiguration inbound neighbor 2001:0DB8::B activate neighbor 2001:0DB8::B route-server-client neighbor 2001:0DB8::B route-map RSCLIENT-B-IMPORT import neighbor 2001:0DB8::B route-map RSCLIENT-B-EXPORT export neighbor 2001:0DB8::B soft-reconfiguration inbound neighbor 2001:0DB8::C activate neighbor 2001:0DB8::C route-server-client neighbor 2001:0DB8::C route-map RSCLIENT-C-IMPORT import neighbor 2001:0DB8::C route-map RSCLIENT-C-EXPORT export neighbor 2001:0DB8::C soft-reconfiguration inbound exit-address-family ! ipv6 prefix-list COMMON-PREFIXES seq 5 permit 2001:0DB8:0000::/48 ge 64 le 64 ipv6 prefix-list COMMON-PREFIXES seq 10 deny any ! ipv6 prefix-list PEER-A-PREFIXES seq 5 permit 2001:0DB8:AAAA::/48 ge 64 le 64 ipv6 prefix-list PEER-A-PREFIXES seq 10 deny any ! ipv6 prefix-list PEER-B-PREFIXES seq 5 permit 2001:0DB8:BBBB::/48 ge 64 le 64 ipv6 prefix-list PEER-B-PREFIXES seq 10 deny any ! ipv6 prefix-list PEER-C-PREFIXES seq 5 permit 2001:0DB8:CCCC::/48 ge 64 le 64 ipv6 prefix-list PEER-C-PREFIXES seq 10 deny any ! route-map RSCLIENT-A-IMPORT permit 10 match peer 2001:0DB8::B call A-IMPORT-FROM-B route-map RSCLIENT-A-IMPORT permit 20 match peer 2001:0DB8::C call A-IMPORT-FROM-C ! route-map A-IMPORT-FROM-B permit 10 match ipv6 address prefix-list COMMON-PREFIXES set metric 100 route-map A-IMPORT-FROM-B permit 20 match ipv6 address prefix-list PEER-B-PREFIXES set community 65001:11111 ! route-map A-IMPORT-FROM-C permit 10 match ipv6 address prefix-list COMMON-PREFIXES set metric 200 route-map A-IMPORT-FROM-C permit 20 match ipv6 address prefix-list PEER-C-PREFIXES set community 65001:22222 ! route-map RSCLIENT-A-EXPORT permit 10 match peer 2001:0DB8::B match ipv6 address prefix-list PEER-A-PREFIXES route-map RSCLIENT-A-EXPORT permit 20 match peer 2001:0DB8::C match ipv6 address prefix-list PEER-A-PREFIXES ! ... ... ...
If you compare the initial configuration of RA with the route server configuration above, you can see how easy it is to generate the Import and Export policies for RA from the In and Out route-maps of RA’s original configuration.
When there was no route server, RA maintained two peerings, one with RB and another with RC. Each of this peerings had an In route-map configured. To build the Import route-map for client RA in the route server, simply add route-map entries following this scheme:
route-map <NAME> permit 10 match peer <Peer Address> call <In Route-Map for this Peer> route-map <NAME> permit 20 match peer <Another Peer Address> call <In Route-Map for this Peer>
This is exactly the process that has been followed to generate the route-map RSCLIENT-A-IMPORT. The route-maps that are called inside it (A-IMPORT-FROM-B and A-IMPORT-FROM-C) are exactly the same than the In route-maps from the original configuration of RA (PEER-B-IN and PEER-C-IN), only the name is different.
The same could have been done to create the Export policy for RA (route-map RSCLIENT-A-EXPORT), but in this case the original Out route-maps where so simple that we decided not to use the call WORD commands, and we integrated all in a single route-map (RSCLIENT-A-EXPORT).
The Import and Export policies for RB and RC are not shown, but the process would be identical.