BGP soft-reconfiguration inbound command

[johnlloyd_13]

hi,

i'm going to configure a new BGP neighbor peer and would like to apply some best practice.

doing some reading on BGP soft in command.

is this command still needed in today's network? can i omit this command line?

is route refresh enabled by default on "newer" cisco routers? is this feature the reason why we can omit the "soft in" command?

what if for some reason the remote peer router is using an older/legacy router and i'm using a new router? do i still need to apply this command? is there a show command to verify if peer doesn't support route refresh capability?

https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_bgp/configuration/15-mt/irg-15-mt-book/irg-soft-config.html

<OUTPUT SNIP>

  BGP state = Established, up for 20w4d

  Last read 00:00:00, last write 00:00:25, hold time is 180, keepalive interval is 60 seconds

  Neighbor sessions:

    1 active, is not multisession capable (disabled)

  Neighbor capabilities:

    Route refresh: advertised and received(new)

    Four-octets ASN Capability: advertised and received

    Address family IPv4 Unicast: advertised and received

    Graceful Restart Capability: received

      Remote Restart timer is 120 seconds

      Address families advertised by peer:

        IPv4 Unicast (was not preserved

    Enhanced Refresh Capability: advertised

    Multisession Capability:

    Stateful switchover support enabled: NO for session 1

  Message statistics:

    InQ depth is 0

    OutQ depth is 0

[balaji.bandi]

Soft Reconfig and Route Refresh - 2 Different things.

if both the side Route Refresh is configured you do not need soft reconfig here.

Soft Reconfig - its pre-stored information and updates any policy changes. this required some resources of routers (which is not make any sense sometimes)

Route refresh capability is the most preferred method…when you change your BGP policy you just send a message to your BGP neighbor and it will re-send you all its prefixes, there will be no disruption at all.

[paul driver]

Hello

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@johnlloyd_13 wrote:

is this command still needed in today's network? can i omit this command line?

is route refresh enabled by default on "newer" cisco routers? is this feature the reason why we can omit the "soft in" command?

what if for some reason the remote peer router is using an older/legacy router and i'm using a is there a show command to verify if peer doesn't support route refresh capability?

  Neighbor capabilities:

    Route refresh: advertised and received(new)

    Four-octets ASN Capability: advertised and received

    Address family IPv4 Unicast: advertised and received   

---

No. It isn’t if RR is supported and you show in your op how to check if your rtr and its peer are RR capable  “advertised and received(new)”

Show ip bgp neigbour | in cap

If the neighbour router doesn’t support any capability you would see this is the above output as not received plus you would probably receive any error message, lastly you can turn off negotiation with the following neighbour command -

neigbour x.x.x.x.x don’t-capability-negotiate < capability > 

[MHM Cisco World]

is this command still needed in today's network? can i omit this command line? If your Peer support route refresh then sure no need, SOFT IN command make router save all BGP receive from the Peer in your router memory, so if you receive 100000 and you use only 10, the SOFT IN keep all 100000 in your router memory but the show ip bgp show only 10 prefix. 

[MHM Cisco World]

I will share lab for this case tonight I hope.

[MHM Cisco World]

the lab is simple I config three LO in R1 and advertise it via BGP 
in R2 i apply IN prefix filter permit only 1.1.1.1/32 
you can see that show ip bgp show only one prefix which is 1.1.1.1/32
but 
show ip bgp summary show 3 prefix receive (meaning the three prefix save in memory of R2) 
so if the router support route refresh it better to not config soft IN.
that my opinion.