| |
|
|
aggregate-address
Creates a conditional aggregate in a BGP routing table.
Syntax: [no] aggregate-address address mask as-set [summary only] [suppress-map map-name] [attribute map map-name]
address
Aggregate address.
mask
Aggregate mask.
as-set
(Optional) Creates autonomous system set path information.
summary only
(Optional) Filters all specific (non-summarized) routes from updates.
suppress-map map-name
(Optional) Name of route map used to identify routes to be suppressed.
attribute map map-name
(Optional) Name of route map used to set the attributes of the aggregate route.
Description: Aggregation is the process of combining the characteristics of several different routes in such a way that a single route is advertised. Aggregates are used to minimize the size of routing tables.
You can configure aggregate routes in BGP either by redistributing an aggregate route into BGP or by using the conditional aggregation.
Use the aggregate-address command with no arguments to create an entry in the BGP routing table if there are more-specific routes that fall in the defined range. The created aggregate route is advertised as originating from your autonomous system. The atomic aggregate attribute is set to show missing information.
Use the as-set keyword to create an aggregate entry that includes as-set information in the routing updates. Each autonomous system number is listed only once, no matter how many times it appeared in the multiple paths that were aggregated. Use the as-set option where aggregation would otherwise cause loss of as-path information.
NOTE Do not use this form of the command when aggregating large numbers of paths. Doing so may cause this route to "flap" (repeatedly withdrawn and re-advertised) as autonomous system path reachability for the summarized route changes.
Use the summary only keyword to create an aggregate route and suppress the advertisement of more-specific routes to all neighbors. Use the neighbor distribute-list command to suppress advertisement to specific neighbors.
Use the suppress-map keyword to create an aggregate route and apply a route map to suppress the advertisement of more-specific routes.
CAUTION If you aggregate routes and a more-specific route leaks into BGP, all BGP speakers prefer the leaked route over the aggregate route.
Use the attribute-map keyword to create an aggregate route and apply a route map to set or modify attributes for the aggregate route.
Use the no aggregate-address command to disable conditional aggregates in the BGP routing table.
Factory Default: Disabled.
Command Mode: Router configuration.
Example 1: In the following example, the aggregate-address command creates an aggregate entry in the BGP routing table:
router(config)#router bgp 120
router(config-router)#aggregte-address 10.1.1.49 255 255 255 240
The route is advertised as coming from autonomous system 120. The prefix route and all the more specific routes are advertised. The atomic attribute is set to show missing information.
Example 2: In the following example, the aggregate-address command creates an aggregate entry in the BGP routing table that includes as-set information:
router(config)#router bgp 120
router(config-router)#aggregate address 190.0.0.0 255 0 0 0 as-set
The route prefix and more-specific routes are advertised with as-set information in the path information of the routing updates. The as-set consists of all the as-path elements of all the paths that are summarized.
Example 3: The following example aggregates 190.0.0.0, suppresses the more-specific 190.200.0.0 but advertises 190.100.0.0:
- The access-list command creates an access list named ISP5_no190.2 to deny route advertisements from network 190.200.0.0 and to permit all other routes.
- The route-map command creates a route map named boston that includes a match clause for the entries in access list 10.
- The aggregate-address suppress-map command creates an aggregate route and to applies the route map boston to aggregate route advertisements:
router(config)#access-list ISP5_no190.2 deny 190.200.0.0 0.0 255.255
router(config)#access-list ISP5_no190.2 permit 0.0.0.0 0.255.255.255
router(config)#access-list ISP5_no190.2 deny any
router(config)#route-map boston
router(config-route-map)#match ip address ISP5_no190.2
router(config)#router bgp 120
router(config-router)#neighbor 120.5.1.121 remote-as 100
router(config-router)#neighbor 120.5.1.190 remote-as 100
router(config-router)#network 140.10.0.0
router(config-router)#aggregate address 190.0.0.0 255 0 0 0 suppress-map boston
Related Commands: match as-path
match ip address
route-map
| |
|
|
Copyright © 2004
Avici Systems Inc.
Avici® and TSR®
is a registered trademark of Avici Systems Inc.
IPriori™, Composite Links™, SSR™, QSR, and NSR® are
trademarks of Avici Systems Inc.
Source
File Name: Routing_Pol.fm
HTML File Name: Routing_Pol3.html
Last Updated: 05/10/04 at 16:38:37