[c-nsp] Best Practices to make one BGP link prefer for egrees and ingress traffic of one subnet

[Muhammad Atif Jauhar]

Hi,

I would like to seek your expert guidance on a BGP traffic engineering
scenario in our current network design.

We have two eBGP uplinks with our Service Provider and are advertising
three internal network prefixes, which are learned via OSPF from our
downstream infrastructure.

Our design requirement is as follows:

   -

   Prefer *Link #1* as the primary egress/ingress path for the following
   prefixes:
   -

      192.168.1.0/24
      -

      192.168.2.0/24
      -

   Prefer *Link #2* as the primary egress/ingress path for:
   -

      192.168.3.0/24

All three prefixes are being redistributed into BGP from OSPF. In the event
of a failure of either BGP uplink, the remaining active link should
automatically serve as the backup path for all advertised prefixes,
ensuring uninterrupted connectivity.

For inbound traffic, we are currently influencing path selection using
AS-Path Prepending on a per-prefix basis.

However, for outbound traffic, we are presently relying on Policy-Based
Routing (PBR) to steer traffic via the preferred uplink. While this
approach is functional, we would prefer to achieve the desired path
selection using BGP-native mechanisms, if possible, to ensure better
scalability and operational simplicity.

We would appreciate your recommendation on best practices to implement
prefix-based outbound traffic engineering using BGP attributes (such as
Local Preference, MED, communities, etc.) instead of relying on PBR.

Your insights on a more optimal and scalable design approach would be
highly valuable.


Regards,

Muhammad Atif Jauhar