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simply used for testing and backup. They chose not to implement two channel-attached routers for
redundancy, but they did select to use two CIPs in a single channel-attached router. This created
higher availability than they had previously, and provided an option in the future to separate CIP
Migration Scenarios 3-11
Scenario 3: Single CIP to Multiple Host
functionality across multiple CIPs. In the future they plan to add TN3270 server capability to the CIP
to allow access to VTAM applications from Web-based clients, and they also anticipate a need for
TCP/IP on the mainframe. Figure 3-9 shows the logical configuration.
Figure 3-9 Dual CIPs in a Single Router
CIP CIP
LLC2 LLC2
502 505
4000.3745.5001 4000.3745.5001
Virtual
Ring
501
Token Ring Interface Processor
4000.7123.FF01 4000.7123.FF02
Ring 200
Ring 201
Router Configuration
!
source-bridge ring-group 501
int tok 0/0
source-bridge 200 1 501
int tok 0/1
source-bridge 201 2 501
!
interface Channel1/0
no ip address
csna 0100 70
!
interface Channel1/1
no ip address
csna 0101 80
!
interface Channel1/2
no ip address
no keepalive
lan TokenRing 0
source-bridge 502 1 501
adapter 0 4000.3745.5001
lan TokenRing 1
source-bridge 505 1 501
adapter 1 4000.3745.5001
!
3-12 Data Center Design and Implementation: SNA Internetworking
Scenario 4: Migrating to APPN
Scenario 4: Migrating to APPN
In the Before environment, the FEP provided SNA routing. The FEP can be replaced without loss of
function by implementing APPN in a channel-attached router. APPN was being considered for this
data center even if the FEP were not being replaced. Recent enhancements to VTAM s APPN
implementation simplify network definition and enhance availability.
This scenario shows the replacement of the FEP with a Cisco router running APPN/DLUR. One host
is configured as an NN and the other as an EN. The NN provides NN server function for the EN and
provides DLUS functionality. Figure 3-10 illustrates this scenario.
Note For more detail on APPN, refer to the Cisco APPN Design and Implementation guide.
Figure 3-10 APPN Scenario
Before
Token
3745-410
Ring
Token
Ring
After
4700s with DLUR 7000/7500
Token
Ring
Token
Ring
7000/7500
Reasons for Change
This enterprise was interested in simplifying their SNA network and reducing their FEP dependency
to reduce costs. They also wanted to improve throughput at the data center. Although they were
starting with APPN/ISR routing, they intend to migrate to HPR in the future. With HPR, loss of a
channel gateway, LAN adapter, or channel adapter can be dynamically recovered without disrupting
end-user sessions.
Design Choices
This enterprise chose to put DLUR functionality in their existing data center routers to maximize the
scalability of their channel-attached routers and minimize the cost of their total network. In addition,
when they migrate to HPR, this design will allow them to nondisruptively reroute around the failure
of a channel-attached router by configuring the channel-attached router as an ANR node.
Migration Scenarios 3-13
APPN in a Parallel Sysplex Environment
Router Configuration
This partial router configuration shows that there are three required parameters and one optional
parameter for defining an APPN connection. Refer to the VTAM configuration manuals for more
details on the changes required to VTAM.
The APPN CONTROL-POINT command is used to identify the router.
The LINK-STATION defines the connection to the router. (This statement is required in at least one
of two APPN nodes connected over a link.)
The PORT defines a point of connection into the APPN network.
The APPN ROUTING command is optional and will automatically start APPN routing when the
router is started.
4700 Router Configuration
version 11.0
!
hostname RTRA
!
enable password cisco
!
appn control-point NETA.RTRA
dlus NETA.VTAMA
dlur
complete
!
!
appn link-station linkA
complete
!
appn port porta dlsw
complete
!
appn routing
!
end
APPN in a Parallel Sysplex Environment
APPN is required in VTAM, at a minimum, in order to take advantage of a Parallel Sysplex
environment. In the Before picture illustrated in Figure 3-11, APPN is implemented in each VTAM
host, while the FEPs and the rest of the network continue to use subarea protocols. This environment
allows SNA sessions to take advantage of generic resources. The Generic Resource feature of VTAM
enables end-user sessions to be dynamically spread across alternate, identical images of an
application. The end user logs on to a generic resource (for example, CICS), and the CMC host
(which is also an ICN) establishes the session with a specific application (perhaps CICS01) running
in one of the migration data hosts. The CMC/ICN balances CICS sessions across all the sysplex
processors, and recovery from the failure of any single processor is disruptive but dynamic. In
VTAM V4R4 and the latest CICS, this recovery will be nondisruptive, using a facility know as
Multi-Node Persistent Sessions (MNPS).
In the After picture shown in Figure 3-11, data center routers provide DLUR function for legacy
traffic. The Cisco channel-attached router can handle the capacity of multiple FEPs, so there are only
two channel-attached routers in the After picture. The DLUR function was installed in existing data
3-14 Data Center Design and Implementation: SNA Internetworking
Scenario 5: Migrating from SNI to APPN
center routers to maximize scalability and availability. The DLUR router routes traffic directly to the
correct migration data host using APPN routing. (In the After picture, if there were really no FEPs,
you could convert the ICNs to NNs and the MDHs to ENs.)
Figure 3-11 Parallel Sysplex Environment
APPN
Before CMC1 /ICN1 MDH 1 MDH 2 1CN2/CMC2
ESCON Coupling
Director Facility
ICN1/DLUS MDH1 MDH2 ICN2 / DLUS (Backup)
After
ESCON Coupling
Director Facility
APPN
NN/DLUR NN/DLUR
Scenario 5: Migrating from SNI to APPN
In the Before environment, Enterprise A connected to a value-added network over a back-to-back
SNI connection. Enterprise A had a small network with a single FEP. They wanted to eliminate the
FEP, but they were using it for SNI.
In the After environment, the FEP in Enterprise A has been replaced with a Cisco channel-attached
router. In the first phase, the router was configured for local DLSw+ conversion from LAN to SDLC.
In the second phase, for which the configuration in Figure 3-12 applies, APPN/DLUR functionality
was added to allow the channel-attached router to directly route all steady-state session traffic going
to the value-added network, without requiring VTAM. In the value-added network, VTAM
migrated to become an ICN. It continues to use subarea protocols for attaching to other networks,
Migration Scenarios 3-15
Scenario 5: Migrating from SNI to APPN
but uses APPN for attaching to this network. In the future, as more enterprises select this
connectivity option, the value-added network provider hopes to replace some FEPs with Cisco
channel-attached routers.
Note For more detail on APPN, refer to the Cisco APPN Design and Implementation guide.
Figure 3-12 SNI Scenario
Before
Value Added
Enterprise A Network
NETID A NETID B
SNI
Back-to-Back
SDLC
Token
Ring
Value Added
Enterprise A Network
NETID A NETID B
VTAM
VTAM Border
Network SNI Node
Node Back-to-Back /ICN
CNN
SDLC
After
Reasons for Change
Enterprise A was interested in reducing their FEP costs. The value-added service provider had a
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