What are the uses of a looking glass server to BGP protocol?
What specifically does BGP look up on a looking glass server during path selection? Is is looking up the rest of the path-- beyond what it sees on on the path vector delivered to it?
Maybe a naive Q-- however i couldn't make much out of it.
TIA
Looking glass queries show what the current state of the tables are. I.e. if you do something akin to a 'show ip bgp 5.1.2.3' you will see all of the known paths and all of the metrics associated with them. There's a variety of criteria for path selection, but the primary qualifier is the length of the path; shorter paths win out over longer paths, and if path lengths are equal then you're looking at meds, localpref, and other mechanics. If all of these are identical metrics, and the path lengths are the same, the preference will be on the BGP peer with the lower router ID ( typically the loopback or interface of the device that you're peering with )
Looking glass main objective is to let other network administrators visualize how looking glass owner see the Internet IP prefixes.
It is very useful to debug and understand how your prefixes propagates between the autonomous systems.
