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This chapter describes how to configure tunneling for synchronous data link control (SDLC) and high-level data link control (HDLC) traffic using the IBM Data Link Switching (DLSw) protocol.
For conceptual information on how SDLC and HDLC tunneling works, see "How SDLC and HDLC Tunneling Works" later in this chapter. For information about the SHDlc Service parameter, see the SDLC Service Parameters chapter in Reference for Enterprise OS Software.
This section describes how to configure the bridge/router for SDLC and HDLC tunneling, by referring to Figure 233. The figure shows an IBM host connected to an IBM controller through NETBuilder bridge/routers and an IP network.
Before beginning this procedure, complete the following tasks:
Configure ports, paths, SDLC and HDLC tunneling, and data link switching by referring to the example in Figure 233 and completing the steps under "Configuring Router A" and "Configuring Router B." Table 67 lists the commands used in these steps.
Figure 233 
SDLC and HDLC Tunneling Example
To configure router A, follow these steps:
1 . Display the port configuration by entering:
SHow -PORT CONFiguration
2 . Define the IP address for the port through which the router is going to tunnel by entering:
SETDefault !1 -IP NETaddr = 129.213.1.1
3 . Set the port ownership of serial port 7 to SHDlc by entering:
SETDefault !7 -PORT OWNer = SHDlc
The number of SHDlc ports a NETBuilder II bridge/router can support is the number of WAN paths it can operate simultaneously.
4 . Display attributes for all available paths by entering:
SHow -PATH CONFiguration
5 . Set the attributes for the SHDlc line by entering:
SETDefault !7 -PATH CLock = External
SETDefault !7 -PATH CONNector = RS232
SETDefault !7 -PATH LineType = Leased
SETDefault !7 -PATH BAUD = 19.2
SETDefault !7 -PATH DUplex = Full
If you use a single- port WAN adapter, set the -PATH ENCoding parameter to NRZ.
SHDLC only supports full-duplex operation.
After configuring values using the PATH Service, you may receive a message telling you to re-enable the path. If you receive this message, re-enable the path with the SETDefault !<path> -PATH CONTrol = Enable command.
6 . Enable the transmission of TCP keepalive packets by entering:
SETDefault -TCP CONTrol = KeepAlive
7 . Specify the number of contiguously missed keepalive packets that brings down the TCP session.
SETDefault -TCP KeepAliveLimit = 3
8 . Configure an IP address to connect traffic to and from the router.
To map the specified DLSw tunnel to the local IP address of bridge/router A, enter:
SETDefault -DLSw Interface = 129.213.1.1
All Internet addresses for connected bridge/routers must be known in the local bridge/router's routing table, either dynamically through RIP or OSPF, or statically configured in the IP routing tables.
9 . Enable data link switching for SNA traffic on the port by entering:
SETDefault -DLSw CONTrol = (EnableSNA, DisableNetBIOS)
10 . Configure the DLSw tunnel peer IP connection by entering the following command. You also must specify the tunnel ID, a peer network address, and optionally, a name for the tunnel connection.
ADD !1 -DLSw PEer 129.213.1.2
11 . From the peer router, display the format of the peer MAC address by entering:
SHow -SYS MacAddrFormat
12 . To display the local MAC address on the SuperStack bridge/router, enter:
SystemInfo
13 . To convert the MAC address to noncanonical format, you must enter the MacAddrConvert command on a NETBuilder II bridge/router. This command is not available on the SuperStack bridge/router.
14 . Display the peer router MAC address by entering:
SHow -PATH MacAddress
15 . Set the MAC address for the peer serial port that the local SDLC port is communicating with by entering:
SETDefault !7 -SHDlc PEer = %10005A265BED
To configure router B, repeat steps 1-11 in the preceding procedure, then continue with the following steps (performed on a NETBuilder II bridge/router):
1 . If the peer MAC address displayed is in canonical format, set it to noncanonical by entering:
SETDefault !7 -SYS MacAddrFormat - Noncanonical
2 . Display the peer router MAC address by entering:
SHow -PATH MacAddress
3 . Set the MAC address for the peer serial port that the local SDLC port is communicating with using:
SETDefault !<port> -SHDLc PEer
After you have configured a tunnel connection using data link switching, you can display information to verify the connection.
To display complete configuration information, enter:
SHow -DLSw CONFiguration
The display shows the settings you have configured.
To display the peer information, enter:
SHow -SHDLc -PEer
The following display is an example of this information:
----------------------------SHDlc PEer-----------------------------
Local Port Local MacAddress Circuit State Peer MacAddress
!4 %1000405011DC CONNECTED %100040605D8A
When shown in the display, SAP E8 represents an HDLC tunnel.
To display the status of circuits, enter:
SHow -DLSw CIRcuits
Information similar to the following is displayed:
The SDLC and HDLC tunneling features enable NETBuilder II bridge/routers to send SDLC or HDLC frames across IP networks through DLSw tunnels. Two bridge/routers interconnect a point-to-point SDLC or HDLC link. They encapsulate SDLC or HDLC frames sent between the two end points and tunnel them through an IP network.
A typical use of SDLC and HDLC tunneling is to connect a host computer and a remote terminal or controller. In Figure 233, two end points of an SDLC link (a 3174 controller and a host) are interconnected by two intermediary bridge/routers. The 3174 controller is connected to port 7 on router A, and the host FEP is connected to port 2 on router B.