BGP Hard Reset vs Soft Reset – Comparison Table Included

In BGP terminology, administrators may be required to reset BGP peers. One instance where resetting is required in when inbound filtering is applied on BGP speaking router so as to apply to filter on the received Update message.

2 Ways to Reset a Peer –

  • Hard Reset

  • Soft Reset

While Hard Reset kills the TCP session with BGP neighbor forcing it to restart. This process disrupts the network and considered last resort if soft reset fails.

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Soft Refresh can be of 2 types –

(1) Soft reset with Route refresh

(2) Soft-reconfiguration. 

Soft Refresh with Route Refresh allows BGP peers to request an update without tearing down the entire neighbor relationship. In Soft-reconfiguration option, since a route-refresh request is not sent to BGP neighbour, a copy is stored of BGP routes delivered in the BGP update from our peer.

BGP Hard Reset vs BGP Soft Reset

PARAMETERHARD RESETSOFT RESET
Philosophy
This will tear down the TCP connection between the peers and re-establish the connection with a BGP Open message and proceed with the regular message exchanges between peers.
Soft reset is of 2 types - (1) Soft reset with Route refresh (2) soft-reconfiguration.
Route Refresh allows BGP peers to request an update without tearing down the entire neighbor relationship.
In Soft-reconfiguration option, since a route-refresh request is not sent to BGP neighbor, a copy is stored of BGP routes delivered in the BGP update from our peer.
Direction
Both In and Out
In or Out
Impact
Severely disrupts reachability for all networks
Impacts only those prefixes affected by policy change
Usage
Should be used as last resort when soft reset is not able to address the issue.
Preferred approach.
Memory usage
No additional memory requirement for storing another table.
Requires additional memory since Router now stores another table for each neighbor instead of one BGP table
Convergence time
Very long since Processing of the full Internet table can take a really long time.
Much shorter than hard reset
Prerequisite
No
Both peers may be required to support the Route Refresh capability (for Soft reset with Route refresh feature)
Related commands
clear ip bgp {* | neighbor ip | peer-group}
clear ip bgp {neighbor ip} soft out
clear ip bgp {neighbor ip} soft in

Download the difference table here.

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