BGP Soft Reconfiguration


You are a network engineer responsible for the network for a local fighting tournament. Two of the fighters exchange tactics using BGP to advertise the networks. They don’t want to exchange everything they know so they are a number of inbound route filters. You want to make sure the new filters are applied without resetting the BGP peering…get over here!


  • All IP addresses have been preconfigured for you.
  • Configure EBGP between AS1 and AS2.
  • Advertise network /24 on router Scorpion in BGP.
  • Configure a prefix-list on router SubZero that filters network /24 and apply it to neighbor router Scorpion.
  • Ensure the changes are visible without resetting the BGP peering.




BGP Soft Reconfiguration

Video Solution:

Configuration Files

You need to register to download the GNS3 topology file. (Registration is free!)

Once you are logged in you will find the configuration files right here.

Opt In Image
Do you want your CCNA or CCNP Certificate?

The How to Master series helps you to understand complex topics like spanning-tree, VLANs, trunks, OSPF, EIGRP, BGP and more.

Written by René Molenaar - CCIE #41726

You May Also Like

About the Author: Rene Molenaar

René - CCIE #41726 is the creator of where he shares CCNA, CCNP and CCIE R&S labs. He also blogs about networking on


  1. excellent lab.
    deceptively simple, but if you dig, there is a lot to research here.
    spurred me to look up the difference between “route refresh” capability
    and the received routes from the bgp neighbor “soft-reconfiguration inbound”.


    with NO “soft-reconfiguration inbound”:
    SubZero#clear ip bgp in
    BGP: sending REFRESH_REQ(5) for afi/safi: 1/1
    BGP: send message type 5, length (incl. header) 23

    SubZero#clear ip bgp soft in
    BGP: sending REFRESH_REQ(5) for afi/safi: 1/1
    BGP: send message type 5, length (incl. header) 23

    where as WITH “soft-reconfiguration inbound”:
    there is NO debug output for either
    – clear ip bgp in
    – clear ip bgp soft in

    this seems to imply this disables, or perhaps more aptly,
    it preempts the negotiated “route refresh” bgp capability.


    it seems one way to verify the old “soft-reconfiguration inbound”
    is to issue the “show ip bgp neighbor X.X.X.X received-routes” command.

    with NO “soft-reconfiguration inbound”:
    SubZero#sh ip bgp neighbor received-routes
    % Inbound soft reconfiguration not enabled on

    where as WITH “soft-reconfiguration inbound”:
    SubZero#sh ip bgp neighbor received-routes | b Net
    Network Next Hop Metric LocPrf Weight Path
    * 0 0 2 i
    Total number of prefixes 1


    excerpt from Cisco command refrence:
    If all BGP routers support the route refresh capability, use the “clear ip bgp ipv4”
    command with the “in” keyword.
    You need not use the “soft” keyword, because soft reset is automatically assumed when
    the route refresh capability is supported.

    good lab 🙂

Comments are closed.