Sustaining Engineering has confirmed that what you are seeing is due to the way Spectrum was designed. The limitations are hold-overs to the core design, long before Spectrum managed BGP Peering sessions, that doesn’t allow an interface to have connections to multiple endpoints.
There is an existing Idea posted in the CS Spectrum communities page. Therefore, it is suggested for customer experiencing this limitation, go out to that Idea, and vote it up. See https://communities.ca.com/ideas/235721949.
The Spectrum Product Management team and developers keep a close eye on these requests to see what additional functionality our user community would like to see in the product.
With that said, Product Management is aware of the limitations Spectrum has when modeling multiple peerings on a single interface. Below are the two scenarios that they are currently investigating to see the best way to improve the BGP Peer monitoring.
Issue1: Customer connects to multiple service providers through a single interface which is a common case.
Here customer is connected to two service providers using Lo1 interface, when discovered in Spectrum, Spectrum will establish connection with only one of the providers.
It might be because, Spectrum won’t allow a port model to be connected to multiple ends, should bring in fanout kind of stuff… even manually also user will not be able to create connections because of same reason...
Issue2: When same IP address is used for the interfaces, Spectrum is not detecting the sessions.
Here interfaces are differing, they are in different VRFs and have same IP address assigned.
There are two BGP sessions with provider, but spectrum will discover only one session.
Engineering is investigating the code/MIB objects to determine the root cause of this behavior.
Look for a future release of Spectrum to contain improvements for monitoring multiple BGP Peers from a single interface.