Offers BGP prefix/route summary at Microsoft Enterprise Edge (MSEE) ExpressRoute routers
There is an urgent business need to summarize BGP prefix/route at MSEEs before being propagate to its peers at remote sites i.e. Cloud Gateway Access (CGA) routers in relation to Express Route service (as there is vary limit of allowable prefix entry set at remote CGA routers i.e. default 20 in some case).
This BGP prefix summarization helps reduce the need of large number of prefix entries to be broadcasted from Azure to CGA especially for business case that have large number of spoke VNETs (Hub and Spoke model) leveraging on granular address space of a large prefix.
For example, one of the spoke VNET prefix configuration as below.
192.168.0.0/25 (larger prefix for workload)
- 192.168.0.0/27 (subnet)
- 192.168.0.32/27 (subnet)
- 192.168.0.64/27 (subnet)
- 192.168.0.96/27 (subnet)
192.168.0.128/25 (larger prefix for backup and recovery)
- 192.168.0.128/27 (subnet)
- 192.168.0.160/27 (subnet)
- 192.168.0.192/27 (subnet)
- 192.168.0.224/27 (subnet)
From above example, spoke VNET alone potentially contribute a total number of 40 prefixes (2 address prefix/address space x 20 spoke VNETs) from Azure to CGA over BGP propagation for a 20 spoke VNETs deployment, not forgetting there is Hub and other direct expressroute connection from non hub-spoke deployment through Virtual Network Gateway.
This prefix entries would be reduced significantly to one prefix entry if BGP summarization can be performed at MSEEs leval, which end result is only 192.168.0.0/16 for this particular business case.
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