Concept Guide
Route-refresh and Soft-reconguration
BGP soft-reconguration allows for faster and easier route changing.
Changing routing policies typically requires a reset of BGP sessions (the TCP connection) for the policies to take eect. Such resets cause
undue interruption to trac due to hard reset of the BGP cache and the time it takes to re-establish the session. BGP soft-reconguration
allows for policies to be applied to a session without clearing the BGP Session. Soft-reconguration can be done on a per-neighbor basis
and can either be inbound or outbound.
BGP soft-reconguration clears the policies without resetting the TCP connection.
To reset a BGP connection using BGP soft-reconguration, use the clear ip bgp command in EXEC Privilege mode at the system
prompt.
When you change the BGP inbound policy locally, you need to process the updates received from a peer. The route-refresh capability allows
the local peer to reset inbound information dynamically by exchanging route-refresh requests to supporting peers. When an inbound policy
conguration is changed, then the Dell EMC Networking OS sends a refresh request message asking the peer to re-advertise updates.
Upon receiving the refresh request, the peer advertises the required information after applying the outbound lters. Route-refresh is
negotiated during the BGP session establishment and will be used only if both the BGP peers support this capability.
To determine whether a BGP router supports this capability, use the show ip bgp neighbors command. If a router supports the
route-refresh capability, the following message displays:
Received route refresh capability from peer.
If you specify a BGP peer group by using the peer-group-name argument, all members of the peer group inherit the characteristic
congured with this command.
• Enable soft-reconguration for the BGP neighbor specied.
CONFIG-ROUTER-BGP mode
neighbor {ip-address | ipv6-address | peer-group-name} soft-reconfiguration inbound
BGP stores all the updates received by the neighbor but does not reset the peer-session.
Entering this command starts the storage of updates, which is required to do inbound soft-reconguration. Outbound BGP soft-
reconguration does not require inbound soft-reconguration to be enabled.
• Reset BGP connection using soft-reconguration.
EXEC Privilege mode
clear ip bgp [vrf vrf-name] [* | neighbor-address | as-number | ipv4 | ipv6 | peer-group-name
| dampening | flap-statistics] {soft {in | out}}
– *: Clears all peers.
– neighbor-address: Clears the IPv4 or IPv6 neighbor of this IP address.
– as-number: Clears the peers AS numbers.
– ipv4: Clears information for the IPv4 address family.
– ipv6: Clears information for the IPv6 address family.
– peer-group-name: Clears all members of the specied peer group.
– dampening: Clears all the ap dampening information.
– flap-statistics: Clears the ap statistics information.
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Border Gateway Protocol (BGP)