Ip Bgp Synchronization - Alcatel-Lucent OmniSwitch 6850-48 Cli Reference Manual

ip bgp synchronization

Enables or disables synchronization of BGP prefixes with AS-internal routing information. Enabling this
command will force the BGP speaker to advertise prefixes only if the prefixes are reachable through AS-
internal routing protocols (IGPs like RIP and OSPF).
ip bgp synchronization
no ip bgp synchronization
Syntax Definitions
N/A
Defaults
This command is disabled by default.
Platforms Supported
OmniSwitch 6850, 6855, 6850E, 9000E
Usage Guidelines
•
Use the no form of this command to disable IGP synchronization.
•
A BGP router is not supposed to advertise routes learned through internal BGP updates unless those
routes are also known by the primary internal routing protocol (e.g, RIP or OSPF). However, requiring
all routers in an AS to know all external routes places a heavy burden on routers focusing mainly on
Intra-AS routing. Therefore, disabling synchronization avoids this extra burden on internal routers. As
long as all BGP routers in an AS are fully meshed (each has a direct connection to all other BGP rout-
ers in the AS) then the problem of unknown external router should not be a problem and synchroniza-
tion can be disabled.
•
By default, synchronization is disabled and the BGP speaker can advertise a route without waiting for
the IGP to learn it. When the autonomous system is providing transit service, BGP should not propa-
gate IGP paths until the IGP prefixes themselves are known to be reachable through IGP. If BGP
advertises such routes before the IGP routers have learned the path, they will drop the packets causing
a blackhole.
•
The BGP protocol must be disabled (using the
Examples
-> ip bgp synchronization
-> no ip bgp synchronization
Release History
Release 6.1; command was introduced.
page 25-22
ip bgp status command) before using this command.
OmniSwitch CLI Reference Guide
BGP Commands
June 2012