Systems and methods for routing traffic through a network along Label-Switched Paths (LSPs) that may extend across multiple autonomous systems include performing Internet Protocol (IP) routing lookups as a packet is transmitted along the LSP. In one implementation, a packet having a predetermined value (which may be inserted by an upstream network device) is received at a network device after travelling along a first segment of an LSP. In response to identifying the predetermined label value of the packet, the network device may perform an IP routing lookup using IP routing information included in the packet to identify a next hop for the packet. The network device may then update a label of the packet such that the packet is routed along a second segment of the LSP and transmit the communication packet to the next hop.