This article explains why a BGP (Border Gateway Protocol) session may not be established when an attempt is made to set up such a session between VRF (virtual routing and forwarding) and an outside inet.0 routing table.

A BGP session was unable to be established when the following conditions were met:

• The BGP source was under VRF, and the BGP peer was reached via inet.0.
• Passive mode was configured under VRF BGP, or the other BGP peer reached via inet.0 initiated a TCP connection.

This behavior is explained in the example below.

• (GE-1/1/1)MX960(ge-1/1/2)---------(ge-1/1/3)MX480
• GE-1/1/1: IP address: 13.1.1.1, and it's under VRF.
• ge-1/1/2: IP address: 12.1.1.1, and it's under inet.0.
• ge-1/1/3: IP address: 12.1.1.2, and it's under inet.0 on MX480.
• On MX960, 12.1.1.2 can be reached from VRF; 13.1.1.1 can also be reached from inet.0.
• BGP session was between 13.1.1.1 and 12.1.1.2.
• When passive mode is configured on the MX960 under VRF BGP, or when the MX480 initiates a TCP connection, the BGP session will not be established.

TCP packets initiated by BGP and received from the interface under the primary instance (inet.0) can't be forwarded by Junos to the address of the interface under the VRF instance.

The solution is to configure passive mode on the other BGP peer.

If the other BGP peer is also under VRF, the BGP session will not be established.

• BGP Feature Guide for Routing Devices
• Understanding Junos OS Routing Tables