Peer preference is a configuration parameter used to break the tie between multiple peers in the realm routing table leading to the same Diameter realm. Peer preference is a local configuration parameter and it does not transfer across the chassis. The peer with the numerically lowest preference value is preferred. As a result, peer preference may lose its meaning in the multi-chassis environment because the peers leading to the same realm may be distributed across both chassis.
The scenario can be clarified by the following example:
Peer 1 and Peer 2 are redundant peers and Peer 1 has a lower preference than Peer 2 on both SR nodes.
Because each SR node in Figure: Distributed peer connections has peering connection open to its own PCRF, the local peer preference loses its meaning. Peer 1 is used on BNG1 and Peer 2 is used on BNG2, although it may be needed that Peer 1 is always preferred over Peer 2.
If the peering connections are colocated (Figure: Collocated peer connections), the preference parameter regains its meaning. In this case, Peer 1 is always selected over Peer 2.
