vrIpBgpPeerVersionNegotiated 1.3.6.1.4.1.562.2.4.1.100.6.21.2.12.1.5

This attribute indicates the BGP version number negotiated with this peer through the OPEN message. Currently, only BGP version 4 is supported. BGP will reject the peer connection if our peer proposes a BGP version other than 4.