Dell PowerSwitch S4820T Configuration Guide for the S4820T System 9.112.0P1 - Page 207

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 confederations appear as one AS. Within the confederation sub-AS, the IBGP neighbors are fully meshed and the MED, NEXT_HOP, and LOCAL_PREF attributes are maintained between confederations. To configure BGP confederations, use the following commands. • Specifies the confederation ID. CONFIG-ROUTER-BGP mode bgp confederation identifier as-number • as-number: from 0 to 65535 (2 Byte) or from 1 to 4294967295 (4 Byte). • Specifies which confederation sub-AS are peers. CONFIG-ROUTER-BGP mode bgp confederation peers as-number [... as-number] • as-number: from 0 to 65535 (2 Byte) or from 1 to 4294967295 (4 Byte). All Confederation routers must be either 4 Byte or 2 Byte. You cannot have a mix of router ASN support. Border Gateway Protocol IPv4 (BGPv4) 207