Summarizing Spoke VPC/VNet CIDR Ranges

If you have a large number of Spoke gateways attached to a Transit GW that you are concerned about exceeding the route limit a VGW can carry (100), you can summarize the Spoke VPC/VNet CIDRs.

Prerequisite

Before you can summarize Spoke VPC/VNet CIDRs, you must make sure Spoke gateways all use either the primary gateway or all use the backup gateway, if backup is enabled.

If you see the error below when configuring Spoke VPC/VNet CIDR manual summarization, your Transit network is not ready for summarization.

bgp_summarize_error

In the example shown below, spoke1 primary gateway is in Active state, however spoke2-hagw is in Active state.

spoke_to_transit_inconsistent

This inconsistency can be fixed by force switching spoke2 VPC/VNet to use the primary gateway, as shown below.

force_switchover_spoke2

Specifying Summarized CIDR Ranges

Go to Multi-Cloud Transit > Advanced Config > Edit Transit, select the Transit GW. (This Transit GW is created when you complete Step 1 at the Transit Network workflow.)

After you select Transit GW, scroll down to "Manual BGP Advertised Network List", as shown below. Enter the summarized CIDR ranges and click Change BGP Manual Spoke Advertisement. You can enter a list of CIDRs separated by commas.

bgp_summarize

To disable this feature, simply remove the list to make the entry empty and then click Change BGP Manual Spoke Advertisement.