In some BGP multi-homed environments between networks, it is possible to achieve shorter convergence times by using certain features beyond traditional [RFC4271] BGP rules. One of these features is the so-called BGP advertise-external or best-external, so that Autonomous System Border Routers (ASBRs) also advertise the best externally received path, even though it may not result as the ultimate best path from the selection algorithm.
A label substitution policy in Junos OS provides resources to conserve and control labels in an inter-AS option B Autonomous System Border Router (ASBR) with local VRFs. It provides further instrumentation to be able to discern routes further than by its Route Targets (RTs) and determine a label action for them.
When extending MPLS L3VPNs across more than a single Autonomous System (ASs), multiple interconnect options may be used, as defined in [RFC4364], Section 10. All these options are well-known in the industry, each one with its pros and cons.
Migrations across different router vendor Operating Systems (OSs) are challenging tasks.
I have been recently working in a migration project from another OS to Junos OS. Considering this was performed in a one-time hotcut maintenance window, there was scarce room for live testing and it was needed to be as accurate as possible in previous preparation, testing and configuration fine tuning.
Route leaking across instances is a widely used technique in many networking environments to allow certain end-to-end communication flows conditioned by policies, to implement deterministic flow redirection rules or to influence route distribution and resolution, among others.
The underlying mechanism is based on being able to share routes across different Routing Information Bases (RIBs).