Dell PowerSwitch S4820T Configuration Guide for the S4820T System 9.100.0 - Page 199

Configure clusters of routers where one router is a concentration router and the others are clients who receive their updates from the concentration router. To configure a route reflector, use the following commands. • Assign an ID to a router reflector cluster. CONFIG-ROUTER-BGP mode bgp cluster-id cluster-id You can have multiple clusters in an AS. • 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, Dell Networking OS 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 Dell Networking OS 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 Next Hop *> 7.0.0.0/29 10.114.8.33 *> 7.0.0.0/30 10.114.8.33 *>a 9.0.0.0/8 192.0.0.0 *> 9.2.0.0/16 10.114.8.33 *> 9.141.128.0/24 10.114.8.33 Dell# Metric LocPrf Weight Path 0 0 18508 ? 0 0 18508 ? 32768 18508 701 {7018 2686 3786} ? 0 18508 701 i 0 18508 701 7018 2686 ? 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 Border Gateway Protocol IPv4 (BGPv4) 199