BGP Synchronization and MPLS
I have the following small topology currently setup. But I can I understand how could this be working. R11, R12, and R13 are all running IS-IS as their IGP. R11 and R13 have an I-BGP session between themselves and they are both adverting a remote prefix that lives behind each of them. Since R12 is not running BGP it will drop the packet do to synchronization issue between the BGP and IGP. So to fix this issue I decided to use MPLS. So I enabled MPLS on all three routers which will then fix the issue since R13 is imposing a label and R12 does not have to route the packet but instead switch the packet based on the label so it won't drop it. However, what I don't understand is how does R13 no what label to impose when forwarding the packet towards R12. Is it just imposing label 16 for all the prefixes behind R11 since thats the same label it's using to reach the peering ip on R11. Below is some output from each of the devices. If you need more please let me know.