DELL Networking OS10 BGP Soft Reset with ROUTE REFRESH

Changing routing policies may require a reset of BGP sessions. This can be achieved by using BGP Hard Reset or Soft reset with soft-reconfiguration or Soft Reset with Route Refresh.

Below is a Comparison between BGP Hard Reset, Soft reset, and Dynamic inbound soft Reset.
 

BGP Hard Reset	BGP Soft reset with soft-reconfiguration	Soft Reset with Route Refresh (Preferred method)
Doing BGP hard reset closes the TCP session. i.e the BGP neighborship reestablish.	The TCP session between the peers is not impacted. i.e BGP neighborships is not impacted.	The TCP session between the peers is not impacted. i.e BGP neighborships is not impacted.
The whole process of neighborship formation and route learning is initiated.	Extra memory is required as routing information from neighbor in stored in a separate table. The changes are then applied and stored in the routing table. This method is only recommended for routers which does not support Route Refresh capability.	Route Refresh is sent to the neighbor which responds back with required routing table information.
No need of special configuration	Must configure Neighbor soft-reconfiguration inbound.	No need of special configuration
No special peer capability required by peer	No special peer capability required by peer	Both BGP Peers must support Route Refresh Capability. How to verify if BGP Neighbor supports ROUTE REFRESH capability.
Impacts traffic of whole prefixes of the BGP neighbor	Impacts only the specific prefixes affected by policy change.	Impacts only the specific prefixes affected by policy change.

 

Command Syntax for using Soft Reset with Route Refresh

Command	Explanation
OS10# clear ip bgp * soft in	Activate policies without resetting the BGP TCP session for all BGP Neighbors.
OS10# clear ip bgp <IP address of neighbor> soft in	Activate policies without resetting the BGP TCP session for specified BGP Neighbors.

Why DELL Networking OS10 does not have BGP soft reset outbound?

In DELL Networking OS10, any route-map or prefix list or BGP attributes change is advertised, gracefully, to the relevant BGP peers, hence soft reset outbound not required in DELL OS10. This is the reason why the "clear ip bgp soft out" command is not present in DELL OS10 CLI.
 

How to verify if BGP Neighbor supports ROUTE_REFRESH capability

Check show ip bgp neighbors and verify if the Capabilities received from neighbor has ROUTE_REFRESH(2).

Sample Output: 

R1# show ip bgp neighbors 10.0.0.2
BGP neighbor is 10.0.0.2, remote AS 100, local AS 1   external link

  BGP version 4, remote router ID 2.2.2.6
  BGP state ESTABLISHED, in this state for 01:00:15
  Last read 01:20:12 seconds
  Hold time is 180, keepalive interval is 60 seconds
  Configured hold time is 180, keepalive interval is 60 seconds
  Fall-over disabled

  Received 84 messages
    3 opens, 1 notifications, 5 updates
    69 keepalives, 6 route refresh requests
  Sent 84 messages
    7 opens, 1 notifications, 2 updates
    71 keepalives, 3 route refresh requests
  Minimum time between advertisement runs is 30 seconds
  Minimum time before advertisements start is 0 seconds

  Capabilities received from neighbor for IPv4 Unicast:
    MULTIPROTO_EXT(1)
    ROUTE_REFRESH(2)                          ======================================>Note
    CISCO_ROUTE_REFRESH(128)
    4_OCTET_AS(65)
  Capabilities advertised to neighbor for IPv4 Unicast:
    MULTIPROTO_EXT(1)
    ROUTE_REFRESH(2)
    CISCO_ROUTE_REFRESH(128)
    4_OCTET_AS(65)
  Prefixes accepted 5, Prefixes advertised 3
  Connections established 2; dropped 1
  Maximum prefix limit reached sent 01:03:15 ago
  For address family: IPv4 Unicast
    Allow local AS number 0 times in AS-PATH attribute
   Prefixes ignored due to:
    Martian address  0, Our own AS in AS-PATH 0
    Invalid Nexthop  0, Invalid AS-PATH length 0
    Wellknown community 0, Locally originated 0

  For address family: IPv6 Unicast
    Allow local AS number 0 times in AS-PATH attribute
  Local host: 10.0.0.1, Local port: 179
  Foreign host: 10.0.0.2, Foreign port: 41230

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