Configuring AppleTalk Addresses
| In this section, we examine the configuration of AppleTalk addresses on LAN and WAN interfaces. Before you assign addresses, you should develop a sensible , overall addressing scheme for your network. A few rules govern the addressing. The following are tips to help guide you:
The last recommendation may seem a bit obvious, but let's explore it a bit further by looking at the address assignments for the San Francisco location in the ZIP network. Table 5-2 shows the assignment of AppleTalk network addresses for the ZIP San Francisco location. Table 5-2. ZIP San Francisco AppleTalk Network Assignments
In the ZIP network, ranges of network addresses have been reserved for certain locations. In this case, all San Francisco network addressing is in the range 1 “1000. When troubleshooting network problems, the ZIP network administrators can quickly identify an AppleTalk device as being located in San Francisco based on its network address. Similarly, the range 1 “1000 has been split into smaller parts . The range 1 “10 has been reserved for the server backbone, and the range 11 “900 has been reserved for building floors where user workstations and printers reside. Lastly, the range 901 “1000 has been reserved for the addressing of WAN links. As you can see, this logical approach to network address assignment facilitates quick recognition of the function and location of devices in this AppleTalk network. LAN Interface ConfigurationAll Cisco routers that are routing AppleTalk have a unique AppleTalk network.node address on each of their attached LAN segments. This network.node address is determined dynamically based on either the Phase 1 network number or the Phase 2 cable-range assigned to the interface. Assigning unique addresses to each interface enables the router to know which networks are connected to each interface and where packets for those networks should be sent. As with TCP/IP, each of the five LAN types described in Chapter 3, "The Basics of Device Interfaces," (Ethernet/IEEE 802.3, Fast Ethernet, Gigabit Ethernet, Token Ring/IEEE 802.5, and FDDI) support the concept of dynamically mapping the MAC address found on the LAN adapter to the AppleTalk address assigned to the interface. This address resolution process is supported by AARP, which also plays a role in dynamic node address assignment. When an AppleTalk workstation needs to contact another AppleTalk workstation on the same logical network and doesn't know that station's data-link address, it sends a broadcast requesting that a data-link address be supplied for the desired AppleTalk address. Each station in that logical network examines the request; if a station's MAC address matches the requested AppleTalk address, it responds with its MAC address. Like Address Resolution Protocol (ARP) in TCP/IP, AARP eliminates the need to know which MAC addresses reside on a station's logical network to communicate with other workstations or servers. Many of the WAN protocols do not support a dynamic mapping of data link to AppleTalk addresses, so WAN configuration requires additional AppleTalk address configuration to communicate with other stations across the WAN interface. Note AppleTalk works well with each of the LAN interfaces described in Chapter 3. Although the link-layer protocol for AppleTalk is the same on each of the LAN implementations ” namely, IEEE 802.2 SNAP LLC ”Apple refers to its implementations of AppleTalk on each of the media by different names . Apple refers to AppleTalk over Ethernet as EtherTalk, AppleTalk over Token Ring as TokenTalk, and AppleTalk over FDDI as FDDITalk. Apple has also named each of the link-layer protocols that support AppleTalk over these media. These protocols include EtherTalk Link Access Protocol (ELAP), TokenTalk Link Access Protocol (TLAP), and FDDITalk Link Access Protocol (FLAP). The primary difference among these link-layer types is in their SNAP encapsulation. On Ethernet, Token Ring, and FDDI interfaces, the SNAP encapsulation consists, respectively, of a standard IEEE 802.3, a standard IEEE 802.5 or an FDDI header, and the IEEE 802.2 SNAP LLC header. Naming the link-layer protocols simply makes it easier to discuss the AppleTalk implementation on those media and to reference the drivers that the Apple operating systems need to support AppleTalk on those media. Assigning AppleTalk Phase 1 network numbers on both LAN and WAN interfaces is accomplished with the Cisco IOS interface subcommand appletalk address . This command takes as a parameter the AppleTalk network and node number in the format network.node . The network number supplied must agree with other operational routers already present on the LAN or WAN segment being configured. The node number supplied is a suggested node number. It may change in the dynamic negotiation process described earlier. Although the ZIP network has chosen to implement Phase 2 addressing exclusively, the following is an example of configuring the SF-1 router with an AppleTalk Phase 1 address on its unused interface ethernet 1: SF-1# configure Configuring from terminal, memory, or network [terminal]? Enter configuration commands, one per line. End with CTRL+Z. SF-1(config)# interface ethernet 1 SF-1(config-if)# appletalk address 201.1 SF-1(config-if)# ^Z Assigning AppleTalk Phase 2 cable-ranges on both LAN and WAN interfaces is accomplished with the Cisco IOS interface subcommand appletalk cable-range . This command takes as a parameter a number range of the format start-end that indicates the starting and ending network address numbers to be included in the cable-range. The cable-range supplied must agree with other operational routers already present on the LAN or WAN segment being configured. The command takes as an optional parameter the initial network.node address to be used during dynamic address negotiation. In the following example, we configure the SF-2 router with an AppleTalk Phase 2 cable-range on each of its three LAN interfaces: SF-2# configure Configuring from terminal, memory, or network [terminal]? Enter configuration commands, one per line. End with CTRL+Z. SF-2(config)# interface ethernet 0 SF-2(config-if)# appletalk cable-range 151-200 SF-2(config-if)# interface ethernet 1 SF-2(config-if)# appletalk cable-range 101-150 SF-2(config-if)# interface fddi 0 SF-2(config-if)# appletalk cable-range 1-10 SF-2(config-if)# ^Z After configuring addresses, configuring zone names on the interfaces is the next step in successfully establishing AppleTalk addressing. Zone names on LAN and WAN interfaces are configured using the Cisco IOS interface subcommand appletalk zone . The command takes as a parameter a character string, which is the zone name. The zone name may include alpha, numeric, and special characters. Additionally, characters from the Macintosh special character set may be included. Simply type a colon , followed by the hexadecimal value from the special character set. Zone names are case-sensitive. Multiple zone names can be specified by entering the appletalk zone command multiple times for a given interface. The first zone name specified is considered the primary zone name for that interface. The interface zone configurations must match exactly ”in name and in number of zones ”the zones already configured on the same network segment's operating AppleTalk routers. In the following example, we configure each of the SF-2 router interfaces with a unique zone name: SF-2# configure Configuring from terminal, memory, or network [terminal]? Enter configuration commands, one per line. End with CTRL+Z. SF-2(config)# interface ethernet 0 SF-2(config-if)# appletalk zone Marketing SF-2(config-if)# interface ethernet 1 SF-2(config-if)# appletalk zone Sales SF-2(config-if)# interface fddi 0 SF-2(config-if)# appletalk zone SF Zone SF-2(config-if)# ^Z AppleTalk and Cisco IOS software support the concept of dynamically configuring the network address and zone name(s) for LAN interfaces based on information available from operational routers already present on the network segment. Dynamic configuration is accomplished by placing the interface in discovery mode. Discovery mode is useful when a router is already present on the network segment and has had its network address and zone name(s) manually established via configuration commands (whether these commands are for Cisco IOS routers or other router types). New routers added to that network segment simply acquire their configuration from the established AppleTalk router. Discovery mode also allows for easy reconfiguration of all routers on a network segment because only the manually configured router ”the seed router ”requires manual reconfiguration. The other routers in discovery mode on that network segment relearn their configuration from the reconfigured seed router. For discovery mode to work properly, at least one seed router must be present on the network segment. If all routers on the network segment are placed in discovery mode, no router can establish its AppleTalk configuration and begin passing AppleTalk traffic. Configuring AppleTalk discovery mode on LAN interfaces is accomplished using the Cisco IOS interface subcommand appletalk discovery . This command is typically used in lieu of the appletalk address or appletalk cable-range commands. Alternatively, discovery mode can be established by specifying the network.node address 0.0 as a parameter to the appletalk address or appletalk cable-range command. Regardless of the command used to implement discovery mode, the appletalk zone command is not used. Although discovery mode is not implemented on the ZIP network, the following is an example of configuring AppleTalk on the San Jose router's tokenring 0/0 interface: San-Jose# configure Configuring from terminal, memory, or network [terminal]? Enter configuration commands, one per line. End with CTRL+Z. San-Jose(config)# interface tokenring 0/0 San-Jose(config-if)# appletalk discovery San-Jose(config-if)# ^Z WAN Interface ConfigurationWAN addressing in AppleTalk is similar to LAN addressing in that it is configured using the appletalk address or appletalk cable-range interface configuration subcommand in conjunction with the appletalk zone command. AppleTalk discovery mode is not sup-ported on any WAN interface. In this section, we explore assigning AppleTalk network numbers to point-to-point and multipoint WAN interfaces. Note that WAN interfaces require specific encapsulation methods (such as X.25 or Frame Relay) to operate and that AppleTalk uses these encapsulation methods on the WAN media. All WAN interfaces require unique AppleTalk node addresses, but the specific interfaces on the same WAN share a common cable-range and zone name. Point-to-Point WAN Interface AddressingAs noted in Chapter 4 during the discussion of IP, a point-to-point WAN interface is one that connects exactly two devices. For two routers to route AppleTalk over a point-to-point WAN interface, they both must be configured with the same AppleTalk network number or cable-range on the connected interfaces. Like on a LAN interface, each device on a WAN interface has a dynamically determined unique AppleTalk node number. Configuring AppleTalk network numbers on the point-to-point WAN interfaces is accomplished with the Cisco IOS interface subcommand appletalk address for Phase 1 addresses or the Cisco IOS interface subcommand appletalk cable-range for Phase 2 addresses. Each separate point-to-point WAN connection (or point-to-point subinterface) should be assigned a separate AppleTalk network number or cable range. AppleTalk zone names can also be assigned to the point-to-point WAN interfaces using the Cisco IOS interface subcommand appletalk zone . In the following example, we configure the Seoul-1 router with AppleTalk cable ranges and zone names on each of its point-to-point interfaces (two Frame Relay subinterfaces and one High-Level Data Link COntrol [HDLC] interface): Seoul-1# configure Configuring from terminal, memory, or network [terminal]? Enter configuration commands, one per line. End with CTRL+Z. Seoul-1(config)# interface serial 0.16 point-to-point Seoul-1(config-if)# appletalk cable-range 2901-2901 Seoul-1(config-if)# appletalk zone WAN Zone Seoul-1(config-if)# interface serial 0.17 point-to-point Seoul-1(config-if)# appletalk cable-range 2902-2902 Seoul-1(config-if)# appletalk zone WAN Zone Seoul-1(config-if)# interface serial 1 Seoul-1(config-if)# appletalk cable-range 1901-1901 Seoul-1(config-if)# appletalk zone WAN Zone Seoul-1(config-if)# ^Z Multipoint WAN Interface AddressingThe general issues involved with configuring network protocol addresses on multipoint WAN interfaces were discussed in Chapter 4 with reference to IP. Like IP, AppleTalk can be used with many different multipoint WAN interfaces, including Frame Relay, X.25, ISDN, and ATM. You can configure each of these multipoint WAN interfaces to route AppleTalk by using the IOS interface subcommand appletalk address or appletalk cable-range , as discussed in previous sections. As with the previous interface types, the IOS interface subcommand appletalk zone is required for proper operation of AppleTalk on multipoint WAN interfaces. AppleTalk also requires the specific data link layer address to be mapped to a specific AppleTalk network.node address. This mapping is configured differently for each WAN protocol. The commands used to perform these mappings require a specific network.node address. It is recommended that network.node addresses be supplied as parameters to the appletalk address or appletalk cable-range commands to ensure that the network administrator knows which node addresses are assigned to which routers on the multipoint WAN cloud. For Frame Relay multipoint interfaces, the router needs to map data-link connection identifier (DLCI) numbers on a multipoint Frame Relay interface to an AppleTalk network.node number. Frame Relay Inverse ARP can map the DLCI number to an AppleTalk network and node number dynamically. Alternatively, you can use the interface configuration subcommand frame-relay map appletalk to statically map the Frame Relay DLCI address associated to an AppleTalk network and a node number that are reachable through the multipoint WAN interface. Addressing multipoint X.25 WAN interfaces is similar to addressing Frame Relay interfaces in that both use static map interface configuration subcommands. X.25 interfaces must have their AppleTalk network.node addresses mapped to the X.121 addresses used to set up the virtual circuits between systems. Each virtual circuit is identified by the X.121 address used to set up the connection. Use the interface configuration subcommand x25 map appletalk to establish the static mapping between the AppleTalk address and the X.121 address on a multipoint WAN interface. Addressing multipoint ISDN interfaces also requires static map commands. With AppleTalk, unlike IP, ISDN mapping commands are required for any device that wants to communicate with another device over an ISDN connection. The IOS interface configuration subcommand dialer map appletalk is used to provide the mapping between AppleTalk network.node addresses and the system names and phone numbers used to set up calls over ISDN. The mapping between ATM data-link virtual path identifier/virtual channel identifier (VPI/VCI) addresses and the AppleTalk network.node number on the multipoint ATM interface depends on the types of ATM protocols and virtual circuits used. For AppleTalk, you can use logical link control/SNAP (LLC/SNAP) encapsulation over ATM with both permanent virtual circuits (PVCs) and switched virtual circuits (SVCs). With PVCs, a permanent virtual circuit is established through the ATM network, and packets are identified as being destined for an AppleTalk address at the other end of the specific virtual circuit. With SVCs, AppleTalk packets are identified as being destined for a specific, statically defined ATM link layer address. The ATM switch establishes the virtual circuit on demand when the router requests a connection to the ATM address for a specific AppleTalk network.node address. LLC/SNAP encapsulation with PVCs makes use of the IOS interface configuration subcommand map- group and the IOS global configuration command map-list to map AppleTalk network.node addresses to specific PVCs. LLC/SNAP encapsulation with SVCs makes use of the IOS interface configuration subcommand map-group and the IOS global configuration command map-list to map AppleTalk network.node addresses to the network service access point (NSAP) addresses used to identify the remote devices on the ATM network. Verifying AppleTalk Address ConfigurationVerifying the AppleTalk addresses and other AppleTalk attributes that have been assigned to your interfaces can be accomplished via the EXEC command show appletalk interface . This command provides a complete look at the parameters associated with the AppleTalk configuration of all interfaces. If a specific interface is supplied as a parameter to the command, only the information about that interface is displayed. Following is the output of the show appletalk interface ethernet 0 command executed on the ZIP network's SF-2 router: SF-2# show appletalk interface ethernet 0 Ethernet0 is up, line protocol is up AppleTalk cable range is 151-200 AppleTalk address is 198.72, Valid AppleTalk zone is "Marketing" AppleTalk address gleaning is disabled AppleTalk route cache is enabled In the first line of the output, you can see the administrative and operational status of the interface. During the validation of the AppleTalk configuration of this interface with other operational routers on the network segment, status information is displayed above and on this line. The second line shows the AppleTalk cable-range network address. The third line shows the network.node address and indicates whether the address conflicts with any other address on this interface. The fourth line shows the zone name to which this interface belongs. Additional lines may be present in the output of this command if additional AppleTalk features, such as packet filters, are applied. An example of this situation comes up in the section "Configuring AppleTalk Filtering via Access Lists," later in this chapter. The IOS EXEC show appletalk interface command has an optional form that enables you to see a brief summary of AppleTalk address information and the statuses of all available interfaces on the device. This summarized version is obtained using the show appletalk interface brief command. Following is the output of the show appletalk interface brief command executed on the ZIP SF-2 router: SF-2# show appletalk interface brief Interface Address Config Status/Line Protocol Atalk Protocol Ethernet0 198.72 Extended up up Ethernet1 120.45 Extended up up Fddi0 7.12 Extended up up Loopback1 unassigned not config'd up n/a In addition to verifying the AppleTalk configuration on the interface itself, you can view both the static and the dynamic mappings of the AppleTalk network.node addresses to data-link addresses on the various WAN multipoint media. To do so, use the IOS EXEC commands show frame-relay map, show atm map, and show dialer maps , as demonstrated in previous chapters. |
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