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Whenever there is a change in the routing policy, the BGP session must be cleared or reset for the new policy to take effect. The two methods for resetting a BGP session are hard reset and soft reset.
Clearing a BGP session using a hard reset is not recommended
Soft reset is performed on a per-neighbor basis, does not clear the BGP session and realize new policies filtering action. Soft reset can be realized by two methods:
•A dynamic inbound soft reset is used to generate inbound updates from a neighbor.
•An outbound soft reset is used to send a new set of updates to a neighbor.
Before the BGP Soft Reset Enhancement feature, a soft reset for inbound routing table updates was performed by entering the neighbor soft-reconfiguration command. This command was used to configure the local BGP router to store all received (inbound) routing updates from this neighbor. This method uses too much memory, so it is not recommended.
So we have to use this new method “Soft route refresh capability (i.e. it allows the dynamic exchange of route refresh requests to re-advertisement of the respective outbound routing table)”, both BGP peers must support the soft route refresh, which is advertised in the OPEN message. It does not require pre-configuration and consumes no additional memory resources.
If the soft reset fails, you can still clear the BGP session, but it will have a negative impact upon network operations and should only be used as a last resort.
Outbound resets have never required pre-configuration or storing of routing table updates and remain unchanged by the BGP Soft Reset Enhancement.
When you show BGP routs you will see this symbol before the route * it is means the route is valid, > it is means the route is the best
* and > are status codes which is the Status of the table entry. The status is displayed at the beginning of each line in the table.
* means the table entry is valid
> means the table entry is the best entry to use for that network
" Soft reconfiguration inbound" command is used to update incomming routes with out tearing down the BGP neighbor. Details are already mentioned in above post.
* Mean valid Route
> Mean Best Route
