A router (R1,..., R8) comprising means for: parsing a received Bit Index Explicit Replication, BIER, header of a received BIER packet to obtain source router identification information and destination router identification information for a tunnel bit string included in the received BIER header, the tunnel bit string representing a set of tunnels (1...9), the destination router identification information including destination subdomain and set identifier information for the set of tunnels, identifying a Bit Index Forwarding Table, BIFT, based on at least the source router identification information and the destination router identification information, identifying a first bit position in the tunnel bit string included in the received BIER header, determining a bit string entry in the BIFT based on the first bit position in the tunnel bit string, said bit string entry comprising: - a bit string with a bit position assigned to the tunnel, - forwarding information including bit positions of the tunnels in the BIFT that share an adjacency next-hop (R2,...R8), and - the adjacency next-hop router, obtaining said forwarding information, obtaining said adjacency next-hop router, generating a subset tunnel bit string based on the bit string in said bit string entry and said forwarding information, said subset tunnel bit string including bit positions corresponding to the tunnels sharing said adjacency next-hop router, generating a BIER header including said subset tunnel bit string, and sending a BIER packet including the payload of the received BIER packet and said generated BIER header to said adjacency next-hop. parsing a received Bit Index Explicit Replication, BIER, header of a received BIER packet to obtain source router identification information and destination router identification information for a tunnel bit string included in the received BIER header, the tunnel bit string representing a set of tunnels (1...9), the destination router identification information including destination subdomain and set identifier information for the set of tunnels, identifying a Bit Index Forwarding Table, BIFT, based on at least the source router identification information and the destination router identification information, identifying a first bit position in the tunnel bit string included in the received BIER header, determining a bit string entry in the BIFT based on the first bit position in the tunnel bit string, said bit string entry comprising: - a bit string with a bit position assigned to the tunnel, - forwarding information including bit positions of the tunnels in the BIFT that share an adjacency next-hop (R2,...R8), and - the adjacency next-hop router, - a bit string with a bit position assigned to the tunnel, - forwarding information including bit positions of the tunnels in the BIFT that share an adjacency next-hop (R2,...R8), and - forwarding information including bit positions of the tunnels in the BIFT that share an adjacency next-hop (R2,...R8), and - the adjacency next-hop router, obtaining said forwarding information, obtaining said adjacency next-hop router, generating a subset tunnel bit string based on the bit string in said bit string entry and said forwarding information, said subset tunnel bit string including bit positions corresponding to the tunnels sharing said adjacency next-hop router, generating a BIER header including said subset tunnel bit string, and sending a BIER packet including the payload of the received BIER packet and said generated BIER header to said adjacency next-hop.