System information

Troubleshooting AppleTalk 9-181
AURP
Figure 9-5 A Sample AppleTalk ZIT
AURP
AURP allows a network administrator to connect two or more AppleTalk internetworks through a
foreign network (such as Transmission Control Protocol/Internet Protocol [TCP/IP]) to form an
AppleTalk wide-area network (WAN). The connection is called a tunnel, which functions as a single,
virtual data link between the AppleTalk internetworks, as shown in Figure 9-6.
Figure 9-6 An AppleTalk Tunnel
A router that connects an AppleTalk internetwork to a tunnel (that is, a router that runs AURP) is
called an exterior router. The exterior router sends AppleTalk data packets and routing information
through the foreign network by encapsulating the packets with the header information required by
the foreign network system. The receiving exterior router removes the foreign header information
and sends the packets out the appropriate interface. Packets are encapsulated in User Datagram
Protocol (UDP) headers in the initial implementation of AURP.
When only two exterior routers are connected to a tunnel, that tunnel is called a point-to-point tunnel.
When more than two exterior routers are connected to the tunnel, that tunnel is called a multipoint
tunnel. If all exterior routers connected to a multipoint tunnel can send packets to each other, the
tunnel is said to be fully connected. If one or more exterior routers are not aware of other exterior
routers, the tunnel is said to be partially connected. Each exterior router functions both as an
AppleTalk router within its local internetwork and as an end node in the foreign network that
connects the AppleTalk internetworks.
Network
number
1
2
3
4
5-5
Zone
My
Your
Marketing
Documentation
Sales
AppleTalk Internetwork A
AppleTalk Internetwork C
Foreign Network C
AppleTalk Internetwork B
Router
Router Router