Cisco Cisco IOS Software Release 12.0(22)S
BGP Soft Reset Enhancement
Prerequisites
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Cisco IOS Release 12.0(22)S
Prerequisites
Peers that exchange reachability information must support the soft reset route refresh capability in order to
use the enhancements described in this document. If a peer does not, then the only available soft
reconfiguration option is to use the neighbor soft-reconfiguration command, which initiates the storage of
inbound routing table updates and requires additional memory, followed by the clear ip bgp in command.
use the enhancements described in this document. If a peer does not, then the only available soft
reconfiguration option is to use the neighbor soft-reconfiguration command, which initiates the storage of
inbound routing table updates and requires additional memory, followed by the clear ip bgp in command.
Configuration Tasks
See the following
section for configuration tasks for the BGP Soft Reset
Enhancement feature. This task is required.
Configuring BGP Soft Reset
Whenever there is a change in the routing policy, the BGP session must be reset (cleared) for the new
policy to take effect and the routing table to be reconfigured. Using a hard reset to clear a BGP session
causes cache invalidation and results in a negative impact on network operation.
policy to take effect and the routing table to be reconfigured. Using a hard reset to clear a BGP session
causes cache invalidation and results in a negative impact on network operation.
Soft reset is recommended because it allows routing table policies to be reconfigured and activated
without clearing the BGP session. Soft reset is done on a per-neighbor basis. Soft resets can be inbound
or outbound:
without clearing the BGP session. Soft reset is done on a per-neighbor basis. Soft resets can be inbound
or outbound:
•
When soft reset is used to generate inbound updates from a neighbor, it is called dynamic inbound
soft reset. There are two ways to perform an inbound soft reset, dynamically (using the dynamic
inbound soft reset) and using stored routing update information.
soft reset. There are two ways to perform an inbound soft reset, dynamically (using the dynamic
inbound soft reset) and using stored routing update information.
•
When soft reset is used to send a new set of updates to a neighbor, it is called outbound soft reset.
There is only one way to perform an outbound soft reset.
Note
The dynamic inbound soft reset and inbound soft reset using stored information functions are mutually
exclusive and cannot be configured together. If the inbound soft reset using stored routing table updates is
configured for a neighbor, the dynamic inbound soft update method cannot be used.
exclusive and cannot be configured together. If the inbound soft reset using stored routing table updates is
configured for a neighbor, the dynamic inbound soft update method cannot be used.
Configuring BGP Dynamic Inbound Soft Reset
If both the local BGP router and the neighbor router support the route refresh capability, you can perform
a dynamic soft inbound reset. This type of reset has the following advantages over a soft inbound reset
using stored routing update information:
a dynamic soft inbound reset. This type of reset has the following advantages over a soft inbound reset
using stored routing update information:
•
Does not require preconfiguration
•
Does not require additional memory for storing routing update information