Forwarding inter-switch connection (ISC) frames in a network-to-network interconnect topology

A first network switch, comprising:

• a first network switch element coupled to a physical switch link to transmit a first untagged and not encapsulated frame for a local network over a first logical connection of the physical switch link to a first network switch element of a second network switch coupled to the physical switch link, when the physical switch link is part of an active topology of the local network;
• and
• a second network switch element coupled to the physical switch link to transmit a second untagged and not encapsulated frame for a foreign network over a second logical connection of the physical switch link to a second network switch element of the second network switch coupled to the physical switch link, when the physical switch link is not part of the active topology of the local network, wherein the first network switch element and the second network switch element are nodes within the active topology of the network for receiving frames;
• and
• wherein the first network switch and the second network switch select a link for transmitting each received frame, wherein the selection is made dependent upon a gateway selection rule stipulating that any node receiving a frame on a link other than the first logical connection is designated as a gateway for that received frame, wherein the gateway selection rule is utilized when the physical switch link is part of the active topology upon which the first network switch operates and when the received frame is not associated with a pre-determined link selection.