Aggregating Routes; Configuring Bgp Confederations - Dell C9000 Series Networking Configuration Manual

• Configure the local router as a route reflector and the neighbor or peer group identified is the route
reflector client.
CONFIG-ROUTER-BGP mode
neighbor {ip-address | peer-group-name} route-reflector-client
When you enable a route reflector, the system automatically enables route reflection to all clients. To disable
route reflection between all clients in this reflector, use the no bgp client-to-client reflection
command in CONFIGURATION ROUTER BGP mode. All clients must be fully meshed before you disable route
reflection.
To view a route reflector configuration, use the show config command in CONFIGURATION ROUTER BGP
mode or the show running-config bgp in EXEC Privilege mode.

Aggregating Routes

The system provides multiple ways to aggregate routes in the BGP routing table. At least one specific route of
the aggregate must be in the routing table for the configured aggregate to become active.
To aggregate routes, use the following command.
AS_SET includes AS_PATH and community information from the routes included in the aggregated route.
• Assign the IP address and mask of the prefix to be aggregated.
CONFIG-ROUTER-BGP mode
aggregate-address ip-address mask [advertise-map map-name] [as-set] [attribute-
map map-name] [summary-only] [suppress-map map-name]
Example of Viewing Aggregated Routes
In the show ip bgp command, aggregates contain an 'a' in the first column (shown in bold) and routes
suppressed by the aggregate contain an 's' in the first column.
Dell#show ip bgp
BGP table version is 0, local router ID is 10.101.15.13
Status codes: s suppressed, d damped, h history, * valid, > best
Path source: I - internal, a - aggregate, c - confed-external, r - redistributed,
n - network
Origin codes: i - IGP, e - EGP, ? - incomplete
Network
*> 7.0.0.0/29
*> 7.0.0.0/30
*>a 9.0.0.0/8
*> 9.2.0.0/16
*> 9.141.128.0/24 10.114.8.33
Dell#

Configuring BGP Confederations

Another way to organize routers within an AS and reduce the mesh for IBGP peers is to configure BGP
confederations.
As with route reflectors, BGP confederations are recommended only for IBGP peering involving many IBGP
peering sessions per router. Basically, when you configure BGP confederations, you break the AS into smaller
sub-AS, and to those outside your network, the confederations appear as one AS. Within the confederation
Next Hop Metric LocPrf Weight Path
10.114.8.33 0
10.114.8.33 0
192.0.0.0
10.114.8.33
0 18508 ?
0 18508 ?
32768 18508 701 {7018 2686 3786} ?
0 18508 701 i
0 18508 701 7018 2686 ?
Border Gateway Protocol IPv4 (BGPv4) 239