Hi there,
My answers:
@raman.shcharbakou wrote:
1. what cannot be accomplished with forwarding type RI that can be accomplished with virtual-router type RI?
None of dynamic routing protocols work in forwarding RI.
virtual-router RI supports all dynamic routing protocols + LDP, no RSVP support in VR.
Locally-generated OAM packets like ping cannot be forced to pass forwarding RI table lookup.
@raman.shcharbakou wrote:
2. As far as i understand, forwarding RI can also have interfaces assigned to it.
Does this mean that these intefaces disappear from master RI and also cannot belong to any other RI?
Correct.
3. What actually changes if I attach an interface to the forwarding RI?
Does this mean that all traffic entering this interface will automatically belong to this RI and be routed according to its routing table?
Such config does not commit.
4. Can a virtual-router type RI send packets out of an interface that actually is not assigned to the RI (say routes are imported using rib-groups)?
Yes it can in a general sense, but I discourage You to think of VR or any other RI as some type of walled "container" within physical router. RI is just a separate routing+forwarding table combo, sometimes just a routing table without associated forwarding table. Any packet originated on a router is build by RE CPU (sometimes by FPC CPU) and then is looked up in associated forwarding table. Similarly, a transit packet is also looked up in a forwarding table. Therefore, it's operator's job to make sure the lookup succeeds if the goal is to send pkts out of interface not belonging to a given VR and there are 2 commony used tools for that: rib-groups and "instance-import" policies.
HTH
Thanks
Alex