Ingress router
An "ingress router" is a Label Switch Router that is a starting point for a given Label Switched Path. An ingress router may be an egress router or an intermediate router for any other LSP. Hence the role of ingress and egress routers is LSP specific. Usually, the MPLS label is attached with an IP packet at the ingress router and removed at the egress router, whereas label swapping is performed on the intermediate routers. However, in special cases the ingress router could be pushing label in label stack of an already existing MPLS packet. Note that, although the ingress router is the starting point of an LSP, it may or may not be the source of the under-lying IP packets.
