IPv6 BGP Synchronization keeps all BGP routers updated with the IPv6 addresses of all available routes and networks.
In BGP Synchronization, if an AS (AS100) passes traffic from another AS (AS300) to a third AS (AS400), BGP does not advertise that route until all the routers in AS100 have learned that route from the IGP. In this case, the IGP is iBGP. AS100 must wait until iBGP has propagated that route to all routers within AS100. Then, eBGP advertises the route to external ASs.
In this example, after RTB learns address 6666::6/128 via iBGP. it then advertises the address to RTD.
Sample IPv6 BGP Synchronization
In this example, RTC (AS2) advertises address 6666::6/128 to RTA (AS100). In AS100, RTA and RTB are running iBGP, so RTB learns address 6666::6/128 and is able to reach it via next hop 5.5.5.5 (RTC). Next hop is carried via iBGP. However, to reach the next hop (RTC), RTB must send traffic through RTE, but RTE does not know IP address 6666::6/128.
If RTB advertises 6666::6/128 to RTD (AS400), traffic that tries to reach 6666::6/128 from RTD must pass through RTB and RTE in AS100. However, since RTE has not learned 6666::6/128, all packets will be dropped at RTE.
To configure BGP Synchronization on RTB in AS100:
You can disable synchronization if you do not pass traffic from one AS to another AS through an intermediate AS. You can also disable synchronization if all routers in the intermediate AS run BGP. Disabling synchronization lets you to carry fewer routes in your IGP and allows BGP to converge more quickly.
To disable BGP Synchronization on RTB in AS100:
