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neighbor max-prefix
Enables/disables limiting the number of routes received from a specific external BGP peer.
Syntax: [no] neighbor {ip-address | peer-group-name} max-prefix prefixes [threshold] [warning-only] [drop-routes]
ip-address
IP address of a BGP neighbor.
peer-group-name
Name of a BGP peer group.
prefixes
Specifies the maximum number of acceptable (good routes) allowed from a specific neighbor. Valid values are integers 1 - 4294967295.
threshold
Optional. Specifies the threshold as a percentage of the maximum-prefixes at which warning messages get generated. Valid values are integers 1 - 100. Default value is 70%.
warning-only
Optional. BGP will generate only warning messages without tearing down the BGP peering session.
drop-routes
Optional. Drop all prefixes above the maximum allowed prefixes.
Description: Routing table updates in the Internet can contain thousands of entries. Processing huge numbers of updates can negatively impact the performance of the Avici router. The neighbor max-prefix command specifies the maximum number of routes accepted from an external BGP peer. If this maximum is exceeded, BGP will take one of two actions:
- Tear down the BGP peering session with the specified neighbor, and generate and log a warning message.
- Generate and log a warning message without tearing down the BGP session.
If BGP is configured to tear down the peering session when the threshold is exceeded, sessions are re-established using the clear ip bgp ip-address command. The session is re-established only if the number of routes received from the BGP peer does not exceed the configured maximum.
Use the neighbor max-prefix prefixes command to configure the maximum number of routes that can be received from an external BGP peer.
Use the ip-address argument to configure the maximum number of routes that can be received from the specified neighbor.
Use the peer-group argument to configure the maximum number of routes that can be received from each member of the specified BGP peer group.
Use the optional threshold argument to configure a threshold percentage of the value defined by the prefixes argument. BGP generates a warning message when the number of routes received from the specified peer or peer group exceeds this threshold. The warning message is generated regardless of the use of the warning-only option.
Use the optional warning-only keyword to configure BGP to only generate a warning when the maximum number of routes is exceeded.
Use the optional drop-routes keyword to configure BGP to drop all prefixes above the maximum allowed prefixes.
Factory Default: Threshold of 70%. Warning is generated when the default threshold is exceeded.
Command Mode: Router configuration.
Example 1: In the following example, the neighbor maximum-prefixes command configures the Avici router to:
- Accept only up to 9,000 routes from the specified neighbor.
- Tear down the BGP peer session to the neighbor if the number of routes specified is exceeded.
- Generate a warning if the number of routes from the specified neighbor exceeds 80% of the maximum.
- Drop any routes that exceed the threshold.
- The show ip bgp neighbor command displays the setting:
router(config)#router bgp 101
router(config-router)#neighbor 120.180.3.3 remote-as 125
router(config-router)#neighbor 120.180.3.3 max-prefix 9000 threshold 80 drop-routes
router(config-router)#end
router#show ip bgp neighbor 120.180.3.3
BGP neighbor 120.180.3.3 using remote AS 125
router ID: 0.0.0.0 version: 4
state: Connect time: 0:00:00
def orignat: False ebgp multihop: False
n hop self: False route ref client: False
send comm: False soft reconfig: False
nbr max-prefix: 9000 threshold: 80 Action: Drop Route
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Example 2: In the following example, the neighbor max-prefixes command configures the Avici router to:
- Accept up to 12,000 routes from any member of the specified peer group.
- Generate a warning (do not tear down the peer session) if the number of routes from the specified peer group member exceeds the maximum:
router(config)#router bgp 101
router(config-router)#neighbor ISP-002 max-prefix 12000 warning-only
Related Commands: clear ip bgp
neighbor peer-group (assigning and creating)
neighbor remote-as
show ip bgp neighbors
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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: BGP_Nd.fm
HTML File Name: BGP_Nd31.html
Last Updated: 05/10/04 at 16:36:55