IPv6 Training (Cisco) Using the “synchronization” (IPv6) Command

The “synchronization” (IPv6) Command

By Charles Ross CCNP #CSCO10444244

One important question I’ve been receiving from many CCNA candidates is “What is Synchronization?”

Now for those who are newcomers to routing protocols; “Synchronization” is the process of harmonizing routing advertisements between an Exterior Gateway Protocol (EGP) and an Interior Gateway Protocol (IGP).

In other words, network administrators (like you) use “Synchronization” to synchronize routing advertisements between a BGP router and an IGP network (system).

By default, in an IPv6 environment “Synchronization” is disabled, so that means the IPv6 BGP speaker (router) advertises an IPv6 route to an external BGP neighbor (another autonomous system) without waiting for the IGP network (system).

Network administrators (like you) perform the Cisco IOS Address family configuration command named synchronization on the IPv6 BGP speaker (router) to allow the process to occur. The IPv6 BGP speaker (router) must be running Cisco IOS 12.2(8)T or higher.

Below is the proper syntax and example of using the command:

Syntax: synchronization

Notice, that there are no arguments or keywords used with the command.

Example:

router>enable

router#configure terminal

router(config)#router bgp 550

router(config-router)#address-family ipv6

router(config-router-af)#synchronization

router(config-router-af)#exit-address-family

router(config-router)#exit

router(config)#

In the example above, notice that the router’s prompt is in “Address family configuration” mode when the “synchronization” command is being used; and since the process is enabled on an IPv6 BGP speaker (router), that IPv6 BGP speaker (router) will not advertise a IPv6 route to an external BGP neighboring router unless that route is local or exists in the IGP network (system) first.

If you need to remove the “Synchronization” process from a router, use the word “no” in front of the command like you see below:

router(config-router-af)#no synchronization

I hope this article was very informative and helped you quickly understand the usage of the “Synchronization” Address family configuration command. If you need to learn more; I suggest you visit my website, were you’ll find the latest information regarding Cisco IPv6 Design and Implementation Techniques.

To your success,

Charles Ross

CCNP #CSCO10444244