Reference Guide

Border Gateway Protocol IPv4 (BGPv4) | 247
Timer values configured with the neighbor timers command override the timer values configured with the
timers bgp command.
When two neighbors, configured with different
keepalive and holdtime values, negotiate for new values,
the resulting values will be as follows:
• the lower of the
holdtime values is the new holdtime value, and
• whichever is the lower value; one-third of the new
holdtime value, or the configured keepalive value is
the new
keepalive value.
BGP neighbor soft-reconfiguration
Changing routing policies typically requires a reset of BGP sessions (the TCP connection) for the policies
to take effect. This type of reset causes undue interruption to traffic due to the hard reset of the BGP cache
and the time it takes to re-establish the session.
BGP soft reconfiguration allows you to re-apply policies to a session without resetting the BGP session.
You can perform soft reconfiguration on a per-neighbor basis for either inbound or outbound policies. BGP
soft reconfiguration clears and reapplies policies without resetting the TCP connection.
Use the
clear ip bgp command in EXEC Privilege mode to reset a BGP connection using BGP soft
reconfiguration.
When inbound soft reconfiguration is enabled on a neighbor and you enter the
clear ip bgp soft in
command, the update database stored in the router is replayed and updates are reevaluated. The replay and
update process is triggered only if a route-refresh request is not negotiated with the peer. If a route-refresh
request is negotiated, BGP sends a request to the neighbor and receives all of the peer’s updates.
Command Syntax Command Mode Purpose
neighbor {ipv4-address | ipv6-address |
peer-group-name} soft-reconfiguration
inbound
CONFIG-ROUTER-BGP Enable inbound soft-reconfiguration for the
specified BGP neighbor. BGP stores all
updates received by the neighbor but does not
reset the peer session.
Entering this command starts the storage of updates on inbound routes,
which is required for inbound soft reconfiguration. Outbound BGP soft
reconfiguration does not require inbound soft reconfiguration to be enabled.
clear ip bgp { * | as-number | ipv4-
neighbor-addr | ipv6-neighbor-addr |
peer-group name} {ipv4 unicast | ipv4
multicast | ipv6 unicast} soft [in | out]
EXEC Privilege Clears and reapplies policies on:
*: All peers
as-number: BGP routers that belong to the
specified AS
neighbor-addr: BGP neighbor with specified
IP address
Type of routes to be reapplied:
ipv4 unicast, ipv4 multicast, or ipv6 unicast
in: Reapplies only inbound policies
out: Reapplies only outbound policies