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This information is described in the following sections:
For a complete description of the commands in this chapter, refer to the "CLAW and TCP/IP Offload Commands" chapter of the Cisco IOS Bridging and IBM Networking Command Reference, Volume II. To locate documentation of other commands that appear in this chapter, use the command reference master index or search online.
For information on the CMPC+ feature, which also supports TCP/IP environments, refer to the "Configuring CMPC+" chapter in this publication.
This section provides an overview of the TCP/IP environments supported by the CLAW, TCP/IP offload, and IP host backup. It includes the following topics:
The Cisco IOS implements the CLAW channel protocol to transport data between the mainframe and a Cisco Mainframe Channel Connection (CMCC) adapter in TCP/IP environments. Each CLAW connection requires two devices out of a maximum of 256. Although this allows for a maximum of 128 CLAW connections per interface, a maximum of 32 CLAW connections per interface is recommended.
The CLAW packing feature enables the transport of multiple IP packets in a single channel operation and significantly increases throughput performance between a mainframe and a CMCC adapter. Currently, IBM's TCP/IP stack does not support the CLAW packing feature.
The CLAW packing feature requires changes to the mainframe CLAW driver support. In partnership with Cisco Systems, Interlink Computer Science (now Sterling Software) has made the corresponding CLAW driver change to Cisco IOS for S/390 Release 2 and Interlink TCPaccess 5.2. Customers must make the necessary changes to their host configurations in order to enable the CLAW packing feature.
The TCP/IP offload feature for CMCC adapters delivers the same function as the TCP/IP offload function on the IBM 3172 Interconnect Controller (Model 3), but with increased performance.
The Offload Alias feature allows multihomed IP addresses for offload devices. This feature enables dispatch-based load-balancing access to mainframe hosts through TCP/IP offload devices that are configured on a CMCC adapter. The Offload Alias feature supports load-balancing access to multiple hosts by allowing you to associate multiple real IP addresses with a virtual IP address at the offload device on a CMCC adapter. Each of the real IP addresses is associated with a common single virtual IP address, or alias, for client access.
Figure 250 shows an example of TCP/IP offload devices that are configured on two different CIP adapters, which are connected to multiple mainframe hosts using three different real IP addresses. The figure depicts the benefit that can be achieved when configuring offload alias support on a CMCC adapter in a networking environment that supports MultiNode Load Balancing (MNLB)---such as the MNLB Feature Set for LocalDirector.
The scenario shown in Figure 250 assumes that any of the configured hosts in the offload environment support the same services that a potential client seeks. A client specifies a virtual IP address, 10.2.33.88, as the destination address for those services. Using offload alias support, the virtual IP address 10.2.33.88 represents any of the three hosts (at real IP addresses 10.10.21.5, 10.10.21.3, or 10.10.22.4) as potential offload servers.
Upon receipt of the virtual IP address from a client, a networking architecture that supports MNLB can assess the load at any of the associated real IP addresses of the hosts supported by the offload devices. Based upon the load information, the load-balancing software forwards the packet to a particular real IP address. The destination IP address within the packet always appears as the virtual IP, or alias, address.
You can connect multiple mainframes to a single CMCC adapter using ESCON channel attachment. Often these mainframes run using the ESCON Multiple Image Facility (EMIF), which permits the physical machine to be divided into multiple logical partitions (LPARs). By defining an unused partition on another mainframe, a user can move the operating system from a failed mainframe or mainframe partition to the unused partition. By having multiple paths to each device, the move is accomplished without changing the mainframe software. This function also permits moving an IP stack between multiple operating system images.
On the CMCC adapter, each IP connection is treated as a physical device. The CMCC adapter does not support multiple active paths to a single IP connection (or device). Prior to IP Host Backup, the router configuration had to be changed whenever the mainframe operating system was moved from one mainframe or LPAR to another. The IP Host Backup feature permits the mainframe operating system to be moved from one mainframe to another without requiring a change to the router configuration at the time of the move.
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Note The IP Host Backup feature does not provide single system image or automatic failover to a waiting backup application. Host operator action on the mainframe is required in these instances. |
The following topics in this section provide information that is useful when you are planning to configure CLAW, TCP/IP offload, or IP host backup support:
The CLAW, TCP/IP offload, and IP host backup features are supported on the following router platforms:
You must configure CLAW, TCP/IP offload, and IP host backup features on the physical interface of a CMCC adapter. For a CIP, the physical interface is either 0 or 1. For the CPA adapters, ECPA and PCPA, the physical interface is port 0.
The CMCC adapters provide support for IP clients to communicate with TCP/IP stacks on IBM hosts that are running the following operating systems:
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Note OS/390 Version 2.5 and later does not support the TCP/IP offload feature on a CMCC adapter. |
TCP/IP protocol services are supported by the following TCP/IP software on the host:
Configuring CLAW, TCP/IP offload, or IP host backup support requires that you perform tasks for configuration of the mainframe and the router sides of the network environment.
Often in the mixed network environment of mainframes and LANs, a systems programmer installs and maintains the mainframe side of the network, while a network engineer manages the routers on the LAN side of the network. In such an environment, the successful configuration of CLAW, TCP/IP offload, or IP host backup support requires the close coordination between these job functions at a customer site.
This chapter contains information for both the network engineer and the host systems programmer to properly configure the network devices for CLAW, TCP/IP offload, and IP host backup support. The tasks for configuring this support are organized by whether they are host-related configuration tasks or router-related configuration tasks. In addition, a topic for correlating the mainframe and router configuration is provided so that you can identify the dependencies between the host and router configuration elements and be sure that they are set up correctly.
For more information about the statements that might be defined in an IOCP file for parallel channels and ESCON channels on the CIP or CPA, see the "Defining the Channel Subsystem for the Router" section in the "Configuring Cisco Mainframe Channel Connection Adapters" chapter of this guide.
For information about how to disable the MIH for the unit addresses being used for your CMCC adapter configuration, see the "Disabling the Missing Interrupt Handler" section in the "Configuring Cisco Mainframe Channel Connection Adapters" chapter of this guide.
The following mainframe-related publications might be useful when configuring TCP/IP on the mainframe to support CLAW, TCP/IP offload, and IP host backup support on a CMCC adapter in the router:
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Note The information in this section on configuring the PROFILE.TCPIP data set on the host is provided to help you correlate the host and router configurations. For the latest information about configuring TCP/IP support on the mainframe, refer to your host publications. |
Consider the statements shown in Figure 251 when you perform the tasks to configure the PROFILE.TCPIP data set on the host. The names shown in bold and italic identify the relationship to some of the important configuration names within the PROFILE.TCPIP configuration.
; Device statement---Defines each CIP subchannel. Values CLAW and NONE ; are required. The read-size argument must be 4096. ; ; DEVICE device-name CLAW subchannel-address host-name device-name-on-routerNONE;read-buffers write-buffers read-size write-size ; DEVICE CIP1 CLAW 762 CISCOVM CIP NONE 20 20 4096 4096 ; ; Link statement---Defines a link name and type. Values "IP" and "0" ; are required for CLAW ; ; LINK link-name IP 0 device-name ; LINK CIPL1 IP 0 CIP1 ; ; Home statement---Specifies an IP address for a link ; ; HOME ip-address link-name HOME 172.16.20.2 CIPL1 ; ! ; Routing information (if you are not using the ROUTED SERVER) GATEWAY ; NETWORK FIRST HOP DRIVER PCKT_SZ SUBN_MSK SUBN_VALUE ; 172.16 = CIPL1 4096 0.0.255.0 0.0.20.0 DEFAULTNET 172.16.20.1 CIPL1 1500 0 ! ;START statements---Starts the IP datagram (CLAW) device ; ; START device-name ; START CIP1 !
Figure 252 shows the corresponding claw configuration on the router.
claw C010 62 172.16.20.2 CISCOVM CIP TCPIP TCPIP
The DEVICE statement in the PROFILE.TCPIP data set defines the link type (CLAW) and a user-specified name for the CLAW device according to the following format:
DEVICE device-name CLAW subchannel-address host-name device-name-on-router NONE read-buffers write-buffers read-size write-size
When you configure the DEVICE statement consider the following points:
The LINK statement for CLAW in the PROFILE.TCPIP data set specifies the link type and a name for the link according to the following format:
LINK link-name IP 0 device-name
When you configure the LINK statement for CLAW consider the following points:
The LINK statements for offload support in the PROFILE.TCPIP data set specify the link type and a name for the link and the IP address of the TCP/IP stack in the router according to the following format:
LINK link1-name OFFLOADLINK1 1 device-name LINK link2-name OFFLOADAPIBROAD ip-address device-name link1-name
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Note The HOME statement is replaced by the second LINK statement in TCP/IP offload configuration. |
When you configure the first LINK statement for offload consider the following points:
When you configure the second LINK statement for offload consider the following things:
The HOME statement in the PROFILE.TCPIP data set specifies an IP address for a link according to the following format:
HOME ip-address link-name
When you configure the HOME statement consider the following points:
The GATEWAY statement in the PROFILE.TCPIP data set defines a static route from the host to the router according to the following format:
GATEWAY network first-hop driver packet-size subnet-mask subnet-value
When you configure the GATEWAY statement consider the following points:
The DEFAULTNET statement in the PROFILE.TCPIP data set defines the default gateway for the network according to the following format:
DEFAULTNET first-hop driver packet-size subnet-mask subnet-value
When you configure the DEFAULTNET statement consider the following points:
The START statement instructs the host to start the CLAW device when TCP/IP is started according to the following format:
START device-name
When you configure the START statement consider the following points:
The BSDROUTINGPARMS statement in the PROFILE.TCPIP data set allows you to configure the host to support dynamic routing algorithms using Routing Information Protocol (RIP) with ROUTED or OROUTED.
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Note Do not configure BSDROUTINGPARMS for OMPROUTE, which uses the Open Shortest Path First (OSPF) Protocol. |
Configure the BSDROUTINGPARMS statement according to the following format:
BSDROUTINGPARMS [TRUE|FALSE] link maxmtu metric subnet-mask dest-addr ENDBSDROUTINGPARMS
The following example shows a dynamic routing configuration with the router IP address specified as a point-to-point link:
BSDROUTINGPARMS TRUE CIPL1 4096 0 255.255.255.0 172.16.21.1 ENDBSDROUTINGPARMS
When you configure BSDROUTINGPARMS consider the following points:
The CLAW feature in Cisco IOS software implements the CLAW channel protocol to transport data between the mainframe host and a CMCC adapter in TCP/IP environments. This section describes the configuration tasks required to enable CLAW support on the mainframe and router and includes the following topics:
Refer to the "Configuration Examples" section to see an example of CLAW configurations.
To define a host subchannel supported by the CLAW feature, use the following commands beginning in global configuration mode:
Use the no claw command to remove the CLAW subchannel device.
To assign an IP address to the network interface, use the following command in interface configuration mode:
| Command | Purpose |
|---|---|
Router(config-if)#ip address ip-address mask [secondary] | Assigns an IP address to the network interface. |
To enhance the performance of the CLAW support, you can further define how the interface and the router interoperate by using the following commands in interface configuration mode:
| Command | Purpose | |
|---|---|---|
Step1 | Router(config)# | Selects the CLAW interface on which to configure the options and enters interface configuration mode. The port value differs by the type of CMCC adapter:
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Step2 | Router(config-if)#ip mtu 4096 | (Recommended for CPA interfaces) Sets the MTU size of IP packets sent on the interface to 4096 bytes. The default MTU is 4472 bytes across the channel on a CPA. The CLAW feature cannot accept packets larger than |
Step3 | Router(config-if)#ip route-cache same-interface | (Optional) Includes fast switching support for multiple IP datagram applications running on the same CMCC adapter. |
Step4 | Router(config-if)#no ip redirects | (Required when configuring host-to-host communications through the same interface) Disables the Internet Control Message Protocol (ICMP) flow that notifies the router of a better path when frames are being sent from one host to another host through the router. |
For additional information about configuring other CMCC adapter options such as the data rate for parallel channel interfaces, see the "Configuring Cisco Mainframe Channel Connection Adapters" chapter in this publication.
The TCP/IP Offload feature in Cisco IOS software implements TCP/IP processing on the router using the CLAW protocol. This section describes the configuration tasks required to enable TCP/IP offload support on the router and includes the following topics:
Refer to the "Configuration Examples" section to see an example of an offload configuration.
To define a host subchannel supported by the offload feature, use the following commands beginning in global configuration mode:
Use the no offload command to remove the offload subchannel device.
Mainframe Configuration Tips
To assign an IP address to the network interface, use the following command in interface configuration mode:
| Command | Purpose |
|---|---|
Router(config-if)#ip address ip-address mask [secondary] | Assigns an IP address to the network interface. |
The Offload Alias feature allows you to assign up to eight virtual IP addresses to a single real IP address for an offload device. You must configure TCP/IP offload support before configuring support for offload aliases. Offload aliases are configured on the physical interface of a CMCC adapter.
To configure offload alias support on a CMCC adapter, use the following command in interface configuration mode:
| Command | Purpose |
|---|---|
Router(config-if)# | Assigns a virtual IP address (alias) to the real IP address of an offload device. |
Use the no offload alias command to remove the alias IP address.
Verifying Offload Alias Configuration
To configure and verify offload alias support on a CMCC adapter, perform the following steps:
interface channel 3/1 ip address 10.10.21.1 255.255.255.0 offload E180 83 10.10.21.3 IPCLUST IPCLUST TCPIP TCPIP TCPIP API offload alias 10.10.21.3 10.2.33.88
Step 2 Create a static route from the alias IP address to the real IP address as shown in the following example:
ip route 10.2.33.88 255.255.255.255 10.10.21.3
Step 3 Run a server, such as Telnet, on the host supported by the offload device.
Step 4 From a client device, run Telnet to the host using the alias IP address, which is 10.2.33.88 in this configuration example.
To enhance the performance of offload support, you can further define how the interface and the router interoperate by using the following commands in interface configuration mode:
| Command | Purpose | |
|---|---|---|
Step1 | Router(config)# | Selects the CLAW interface on which to configure the options and enters interface configuration mode. The port value differs by the type of CMCC adapter:
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Step2 | Router(config-if)#ip mtu 4096 | (Recommended for CPA interfaces) Sets the MTU size of IP packets sent on the interface to 4096 bytes. The default MTU is 4472 bytes across the channel on a CPA. Specifying 4096 eliminates fragmentation and increases performance. |
Step3 | Router(config-if)#ip route-cache same-interface | (Optional) Includes fast switching support for multiple IP datagram applications running on the same CMCC adapter. |
Step4 | Router(config-if)#no ip redirects | (Required when configuring host-to-host communications through the same interface) Disables the Internet Control Message Protocol (ICMP) flow that notifies the router of a better path when frames are being sent from one host to another host through the router. |
For additional information about configuring other CMCC adapter options such as the data rate for parallel channel interfaces, see the "Configuring Cisco Mainframe Channel Connection Adapters" chapter in this publication.
To configure the CLAW IP Host Backup, use the following command in interface configuration mode:
| Command | Purpose |
|---|---|
Router(config-if)#claw path device-address ip-address host-name device-name host-app device-app [broadcast] backup | Defines the CLAW subchannel device for backup support. |
For more information about configuring the claw command, see the "Configuring CLAW Support" section.
For more information about configuring the offload command, see the "Configuring TCP/IP Offload Support" section.
To configure the IP Host Backup using paths, use the following commands beginning in interface configuration mode:
| Command | Purpose | |
|---|---|---|
Step1 | Router(config)# | Selects the interface on which to configure the IP host backup paths and enters interface configuration mode. The port value differs by the type of CMCC adapter:
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Step2 | Router(config-if)#path path [[path ...]] | Defines the backup path or paths for this group and enters IP Host Backup configuration mode. |
Step3 | Router(config-if-path)#claw device-address ip-address host-name device-name host-app device-app [broadcast] | Defines the CLAW parameters for this device. |
Step4 | Router(config-if-path)#offload device-address ip-address host-name host-ip-link device-ip-link host-api-link device-api-link [broadcast] | Defines the offload parameters for this device. |
Step5 | Router(config-if-path)#exit | Exits IP Host Backup configuration mode and returns to interface configuration mode. |
Table 13 shows a summary of the configuration elements on the router and host that must be correlated for proper operation of CLAW and TCP/IP offload support. The column labeled "Configuration Element" identifies the type of entity to be configured. The columns labeled "Router Configuration" and "Mainframe Configuration" identify the related parameters on the router and the mainframe whose values must be compatible or match.
| Configuration Element | Router Configuration | Mainframe Configuration |
|---|---|---|
Subchannels | path and device arguments of the claw and offload commands | RESOURCE PARTITION, CHPID, and CNTLUNIT statements of the IOCP definition defining the following parameters for the CLAW or offload channel path:
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Host IP address | ip-address argument of the claw and offload commands |
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Host name | host-name argument of the claw and offload commands | host-name argument in the DEVICE statement of the PROFILE.TCPIP data set. |
Device name | device-name argument of the claw and offload commands | device-name argument in the DEVICE and statement of the PROFILE.TCPIP data set. |
For a complete list of the show commands that are related to monitoring CMCC adapter interfaces, see the "Configuring Cisco Mainframe Channel Connection Adapters" chapter in this publication. To display the full list of show commands, enter show ? at the EXEC prompt.
To display information related to CLAW and TCP/IP offload configurations, use the following commands in EXEC mode:
The following sections include examples to help you understand different aspects of interface configuration:
ip address 197.91.2.5 255.255.255.0
claw 0100 00 197.91.2.2 VMSYSTEM C7000 TCPIP TCPIP
interface Channel0/0 ip address 172.18.4.49 255.255.255.248 no keepalive claw C010 F2 172.18.4.50 HOSTA RTRA PACKED PACKED claw C020 F4 172.18.4.52 HOSTB RTRA TCPIP TCPIP claw C030 F6 172.18.4.53 HOSTC RTRA PACKED PACKED
The following example shows a CLAW definition in the host configuration file for IOS/390:
000100 *--------------------------------------------- 000200 * Member: IOS390R2.V510.PARM(TCPCFGxx) 000300 * Description: TCP task group configuration 000400 *--------------------------------------------- 000500 000600 * Define the virtual medium 000700 000800 MEDIA VIRTUAL MTU(4096) NAME(LOOPBACK) 000900 001000 * Define the physical medium 001100 001200 MEDIA CLAW MTU(4096) NAME(ROGCLAW) ASSIST 001300 001400 * Define the host 001500 001600 NETWORK IPADDRESS(172.18.4.50) 001700 SUBNET(255.255.255.248) 001800 001900 * 002000 002100 CLAW DEVADDR(8f2) 002200 BUFSIZE(32768) 002300 IBUF(5) 002400 OBUF(5) 002500 RESTART(60) 002600 HOSTNAME(HOSTA) 002700 WSNAME(RTRA) 002800 START 002900 PACKED 003000 003100 * Define gateway 003200 003300 ROUTE DEST(0.0.0.0) ROUTE(172.18.4.49) 003400 003500 * Define the transport pr 003600 003700 TCP MAXRCVBUF(131072) 003800 MAXSNDBUF(131072) 003900 DEFRCVBUF(131072) 004000 DEFSNDBUF(131072) 004100 DELAYACK(2) 004200 FASTRX(3) 004300 MAXRXMIT(18) 004400 MINDEV(90) 004500 PORTUSE(1:4095) 004600 PORTASGN(4096:8191) 004700 004800 UDP MAXRCVBUF(64000)005200 PORTUS 004900 MAXSNDBUF(64000) 005000 DEFRCVBUF(64000) 005100 DEFSNDBUF(64000)005300 PORTAS 005200 PORTUSE(1:4095) 005300 PORTASGN(4096:8191) 005400 005500 RAW MAXRCV 005600 MAXSND 005700
The following example consists of the mainframe host profile statements, buffer poolsize recommendations, and router configuration statements for the network shown in Figure 253.
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Host Profile Statements
; Device statement DEVICE OFF CLAW 762 CISCOVM CIP1 NONE 20 20 4096 4096 ! ; Link Statements (both needed) LINK OFFL OFFLOADLINK1 1 OFF LINK MEMD OFFLOADAPIBROAD 162.18.4.59 OFF OFFL ! ; Home Statement ; (No additional home statements are added for offload) ! ! ; Routing information (if you are not using the ROUTED SERVER) GATEWAY ; NETWORK FIRST HOP DRIVER PCKT_SZ SUBN_MSK SUBN_VALUE 162.18 = MEMD 4096 0.0.255.248 0.0.4.56 DEFAULTNET = MEMD 1500 0 ! ;START statements START OFF !
Router Configuration Statements
The following statements configure the offload feature in the router. When you configure a host-to-host communication through the same channel interface, include the no ip redirects and iproute-cache same-interface commands:
interface Channel0/0 ip address 162.18.4.57 255.255.255.248 no ip redirects ip route-cache same-interface no keepalive offload C300 62 162.18.4.59 CISCOVM CIP1 TCPIP TCPIP TCPIP API
Figure 254 shows the architecture for this example and the relationship of the IP addresses on the host and offload devices. The alias IP address for each of the MVS hosts is 10.2.33.88 in this example. Each host has a unique real IP address that is associated with the alias IP address in the offload configuration on the CMCC adapter.
Router 1 Configuration
! Select the physical channel interface ! interface channel 3/1 ! ! Assign an IP address to the channel interface ! ip address 10.10.21.1 255.255.255.0 ! ! Configure other router network characteristics ! no ip directed-broadcast ip route-cache flow no ip mroute-cache no ip redirects no keepalive ! ! Configure TCP/IP offload and alias support to MVS0 and MVS1 ! offload E180 80 10.10.21.3 IPCLUST IPCLUST TCPIP TCPIP TCPIP API offload E180 82 10.10.31.5 IPCLUST IPCLUST TCPIP TCPIP TCPIP API offload alias 10.10.21.3 10.2.33.88 offload alias 10.10.31.5 10.2.33.88
Router 2 Configuration
! Select the physical channel interface ! interface channel 3/1 ! ! Assign an IP address to the channel interface ! ip address 10.10.22.2 255.255.255.0 ! ! Configure other router network characteristics ! no ip directed-broadcast ip route-cache flow no ip mroute-cache no ip redirects no keepalive ! ! Configure TCP/IP offload and alias support to MVS2 ! offload E180 84 10.10.22.4 IPCLUST IPCLUST TCPIP TCPIP TCPIP API offload alias 10.10.22.4 10.2.33.88
Figure 255 shows the backup connection occurring between System B Mainframe 3 when Mainframe 2 fails.
The intent of this backup configuration is that the system named A will be loaded on one of the mainframes in LPAR1 on that mainframe. The DASD for that system will be shared among all the mainframes but only one of them will ever IPL the system at one time. The same holds for LPAR2 and LPAR3.
The ESCON director has the following connections:
The following examples show how to configure IP Host Backup for three mainframe hosts,
Mainframe 1, Mainframe 2, and Mainframe 3, as shown in Figure 255. Each mainframe is configured for at least three logical partitions (LPARs).
Excerpts from the host TCP/IP profiles show how the host might be configured. Excerpts from the router configuration show how the IP Host Backup configuration statements are configured.
Host TCP/IP Profiles
The DEVICE and HOME statements in the nine TCP/IP profiles are similar to the following:
LPAR1 (mainframes 1, 2, 3): DEVICE CIP1 CLAW 630 LPAR1 CIP1 NONE 20 20 4096 4096 LINK CIP1L IP 0 CIP1 HOME 198.92.5.2 CIP1L LPAR2 (mainframes 1, 2, 3): DEVICE CIP1 CLAW 730 LPAR1 CIP1 NONE 20 20 4096 4096 LINK CIP1L IP 0 CIP1 HOME 198.92.5.3 CIP1L LPAR3 (mainframes 1, 2, 3): DEVICE CIP1 CLAW 830 LPAR1 CIP1 NONE 20 20 4096 4096 LINK CIP1L IP 0 CIP1 HOME 198.92.5.4 CIP1L
Router Configuration
On the router, the CIP is located in slot 3 and port 1 is connected to the ESCON director. The path commands define the group of paths that are used as the IP Host Backup.
interface channel 3/1 ip address 198.92.5.1 255.255.255.128 path c010 c110 c210 claw 30 198.92.5.2 lpar1 cip1 tcpip tcpip path c020 c120 c220 claw 30 198.92.5.3 lpar2 cip1 tcpip tcpip path c030 c130 c230 claw 30 198.92.5.4 lpar3 cip1 tcpip tcpip
Posted: Thu Jul 20 10:20:54 PDT 2000
Copyright 1989-2000©Cisco Systems Inc.
