7.8.1.0 - Force10 Networks

Aggregate routes
FTOS 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.
Use the following command in the CONFIGURATION ROUTER BGP mode to aggregate routes.
Command Syntax Command Mode Purpose
aggregate-address ip-address
mask [advertise-map map-name]
[as-set] [attribute-map map-name]
[summary-only] [suppress-map
map-name]
AS_SET includes AS_PATH and community information from the routes included in the aggregated route.
In the show ip bgp command, aggregates contain an ‘a’ in the first column and routes suppressed by the
aggregate contain an ‘s’ in the first column.
Figure 138 Command Example: show ip bgp
Force10#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 Metric LocPrf Weight Path
*> 7.0.0.0/29 10.114.8.33 0 0 18508 ?
*> 7.0.0.0/30 10.114.8.33 0 0 18508 ?
*>a 9.0.0.0/8 192.0.0.0 32768 18508 701 {7018 2686 3786} ?
Aggregate Route
*> 9.2.0.0/16 10.114.8.33 0 18508 701 i
*> 9.141.128.0/24 10.114.8.33 Indicators
0 18508 701 7018 2686 ?
Force10#
Configure BGP confederations
CONFIG-ROUTER-
BGP
Assign the IP address and mask of the prefix to
be aggregated.
Optional parameters are:
• advertise-map map-name: set filters for
advertising an aggregate route
• as-set: generate path attribute information
and include it in the aggregate.
• attribute-map map-name: modify attributes
of the aggregate, except for the AS_PATH and
NEXT_HOP attributes
• summary-only: advertise only the aggregate
address. Specific routes will not be advertised
• suppress-map map-name: identify which
more-specific routes in the aggregate are
suppressed
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 a large number of 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.
246 Border Gateway Protocol