Domain Name Resolver Configuration
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Table Of Contents
Domain Name Resolver (DNR) Configuration
Introducing the Domain Name Resolver (DNR)
Major Components of the Domain Name System (DNS)
Configuring DNR in LOCAL or GLOBAL Mode
Primary DNR Configuration Member (DNRCFGxx)
Controlling DNR Member Processing
Coordinating DNRALCxx and DNRSLCxx Configuration
DNR Alias and Search List Recommendations
Setting Network Preferences (DNRNPCxx)
Setting Network Name to Network Number Mapping (DNRNETxx)
Setting Protocol Name to Address Mappings (DNRPRTxx)
Setting Protocol Name/Service Pair to Port Numbers (DNRSVCxx)
Protocol Name/Service Pair Syntax
Setting RPC Name-to-Program Mappings (DNRRPCxx)
RPC Name-to-Program Mappings Syntax
DNR with Only Configuration Data
DNR With Only The Domain Name System
DNR Configuration Set for a Network with a Domain Name Server
DNR Configuration Set without a Domain Name Server
DNR Configuration Set With a Domain Name Server and a Firewall
Domain Name Resolver (DNR) Configuration
This chapter provides an overview of the information required to customize Cisco IOS for S/390. It includes these sections:
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Introducing the Domain Name Resolver (DNR)
Describes the basic concepts of domain name resolution.
Describes the services provided by the domain name resolver.
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Describes the domain name space, name servers and resolvers.
Provides a quick startup customization for DNR.
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Describes how to set up DNR for local or global resolution.
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Describes DNRCFGxx.
Describes the secondary DNR members such as DNRHSTxx, DNRALCxx, etc.
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Describes DNRHSTxx, which is used to resolve fully qualified domain names to Internet addresses.
Describes the DNRALCxx, which creates fully qualified domain names from partially qualified domain names.
Describes DNRSLCxx, which is used to specify the search list for the DNR component of Cisco IOS for S/390.
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Describes how to coordinate the configuration of DNRALCxx and DNRSLCxx to enable Cisco IOS for S/390 users to specify partially qualified domain names as arguments to DNR requests that require a fully qualified domain name as a search argument.
Describes DNRNSCxx, which is used to specify the name servers assigned various domains for the DNR component of Cisco IOS for S/390.
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Describes DNRNPCxx, which is used is used to order the preferred routes of networks.
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Describes DNRNETxx, which is used to specify network name to network number mappings and vice versa.
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Describes DNRPRTxx, which is used to specify protocol name to address mappings and vice versa.
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Describes DNRSVCxx, which is used to specify the mappings from protocol name/service name pairs to port numbers and vice versa.
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Describes DNRRPCxx, which is used to specify RPC name to RPC program number mappings and vice versa.
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Provides several examples of DNR configurations for different environments.
Introducing the Domain Name Resolver (DNR)
The DNR information base provides information about network objects by answering queries.To obtain information from the DNR, provide the name of some object known to the DNR. The DNR searches for the information associated with that name or attribute and returns the information.
The DNR task group provides services for both Cisco IOS for S/390 and its API application programs. DNR configuration members must be configured with site specific information. Without site specific configuration, Cisco IOS for S/390 itself and Cisco IOS for S/390 users must specify Internet addresses in attempts to communicate with remote hosts. Any site that wants to communicate with hosts by specifying a name must configure the DNR members.
Services Provided by DNR
DNR currently provides these services, with either the dirsrv() API call or the DNRGET TSO command:
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(in other words, TCP or UDP port number)•
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Major Components of the Domain Name System (DNS)
The DNS has these major components:
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A tree structured name space that corresponds to the naming hierarchy of nodes (or hosts) in the name space.
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Hold information about the domain name space and provide answers to resolver's requests.
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Extract information from name servers in response to client requests. DNR implements the resolver portion of the DNS and queries name servers for responses.
Locally Managed Names
Local names consist of those names defined in locally maintained configuration data sets, and can be any one of these types:
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Such names are case insensitive and consist of alphanumeric characters from the EBCDIC character set (a-z, A-Z, 0-9). The dash (-) and underscore (_) characters may also be used as long as they are embedded within the name (in other words, does not appear at the beginning or end of the name). Locally managed names must be less than or equal to 40 characters in length.
Domain Name Specification
The DNS identifies hosts by the hierarchical domain name space. Using domain names, each DNS node is represented by a label which is the simple name of the node. A fully qualified domain name describes a path through the DNS to a particular node, beginning with the top level (root) node. The name is formed by concatenating the simple names (or labels) of each node in right-to-left sequence by periods (.) beginning with the top level domain. A 4-level domain name appears as:
level-4.level-3.level-2.level-1.The period at the end of a domain name represents the root of the DNS and indicates the name is fully qualified. A domain name not terminated with a period is assumed to be partially qualified. The DNR constructs fully qualified names by appending qualifiers from a search list in a predetermined order.
Simple domain names (in other words, domain name labels) are case insensitive and consist of alphanumeric characters from the EBCDIC character set (a-z, A-Z, 0-9). The dash (-) and underscore (_) characters may also be used as long as they are embedded within the name (in other words, do not appear at the beginning or end of the name). Simple domain names must be less than or equal to 63 characters in length, and fully qualified domain names must be less than or equal to 255 characters in length, including the terminating period.
How DNR Resolves Host Names
In order for Cisco IOS for S/390 to make a connection to a host on the network, it must know the IP address of that host before it sends out the first packet. You can either supply the address (for example, Telnet 138.47.118.32), or you can give the name (for example, Telnet hobbes) and do a search to map that name to an IP address. This search is the primary function of DNR.
From FTP2, give the command OPEN HOBBES to connect to the remote host named HOBBES.
To resolve this name into an IP address that can be placed in a network packet, DNR makes these checks:
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Since HOBBES is not a fully qualified name (it does not end in a period), DNR appends the entries found in the DNRSLCxx member in an attempt to create one and checks the DNRALCxx table again (this example uses ND.EDU. and a period (.) as the search list entries). If there is a match at this point, it will be for an entry with an associated IP address and the check is completed.
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If DNR is in LOCAL mode it searches the DNRHSTxx table with the fully qualified names HOBBES.ND.EDU. and HOBBES. If there is no match, DNR returns indicating no match was made.
If DNR is in GLOBAL mode, it sends out queries to all the name servers listed in the DNRNSCxx member for HOBBES.ND.EDU. and HOBBES. If it does not receive a positive response in the allotted time (set by the DNR parameter of the GLOBAL statement in APPCFGxx), it returns indicating a timeout condition. If it receives a negative response from all servers, it returns indicating no match was made.
DNR Suffix Conventions
Like other Cisco IOS for S/390 configuration members, the DNR software ships with all task group members specified with the default 00. In other words, the primary configuration member is DNRCFG00. However, these members can be specified to something other than the default. Therefore, the members described in this document use xx (in other words, DNRCFGxx), to indicate that the last two digits can be specified to your choice.
Caution
It is recommended that you make a copy of the DNRCFG00 that is shipped with Cisco IOS for S/390. If you apply SMP/E maintenance, the original DNRCFG00 may be overwritten.
Initial DNR Customization
Minimal DNR customization must occur before using Cisco IOS for S/390 for the first time. DNR, as distributed, is set to run in LOCAL mode. This means that all host addresses are resolved from either DNRALCxx or DNRHSTxx. Run the initial test in this mode to verify that name resolution is done correctly. If you have network name servers, you can configure DNR to point to them for name resolution. DNR configuration changes are implemented by either stopping (STOP) and starting (START) the DNR task group or by recycling the Cisco IOS for S/390 address space.
Be aware that many Cisco IOS for S/390 services, including SNMP, NFS, and SMTP, do not work properly if DNR is not configured properly.
The initial changes for each of the primary DNR configuration members are shown below.
With these minimum configuration changes in place, Cisco IOS for S/390 is able to resolve its own name and IP address. However, you are not able to address hosts in your network by name with the client commands. To do this, you must add entries for them to either the DNRHSTxx or DNRALCxx members.
You can use the DNRGET command (read the Cisco IOS for S/390 System Management Guide for information about this command) to query DNR and verify it is working correctly.
Configuring DNR in LOCAL or GLOBAL Mode
The DNR task group is an information base that keeps track of hosts in the network. It consists of locally configured information and optional global information. Corresponding to this data, Cisco IOS for S/390 DNR may be configured in LOCAL mode, defined in the GLOBAL statement in member APPCFGxx. Likewise, Cisco IOS for S/390 users may write applications that issue the DIRSRV macro (used to invoke the DNR facilities), specifying LOCAL resolution.
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The configuration data read by the DNR at initialization is contained in these members of the PARM data set. Table 7-1 lists the required member configuration:
Table 7-1 DNR Configuration Members
Secondary DNR Members describes each of the DNR configuration members.
Caution
When customizing the DNR task group, do not change the PARM members that were shipped with Cisco IOS for S/390. These members are under SMP/E control and may be replaced when maintenance is applied. Instead, make a copy of the member you want to customize, changing the default suffix 00 to your own unique suffix (for example, 01).
Primary DNR Configuration Member (DNRCFGxx)
The primary DNR configuration member in the PARM data set is DNRCFGxx. It specifies the main configuration parameters for the DNR task group. It also specifies DNR initialization parameters and the names of the secondary DNR configuration members.
You should make a copy of the default DNRCFG00 in the PARM library and change the last two digits. In this new copy, you should set the APISUBSYS (if different than the default ACSS) and specify the names of the secondary DNR configuration members.
To the default DNRCFG00 member, specify CNFG(xx) in the START DNR command in the STARTxx member of the PARM data set.
POOLDEF Statement Syntax
The first statement in the DNRCFGxx member is the POOLDEF statement.
Caution
The POOLDEF statement specifies the parameters related to a required storage pool named DSRB. This pool must be defined in this member; do not delete this POOLDEF statement as there are no defaults for the associated storage pool.
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Refer to for information on POOLDEF statement syntax.
DNR Statement Syntax
Use this syntax with the DNR statement:
DNR [ALIAS (DNRALCxx)]
[APISUBSYS (subsystem_name)]
[CYCLEMAX (number)]
[HOSTTABLE (DNRHSTxx)]
[INTERNALTRACE | NOINTERNALTRACE]
[MAXSENDS (number)]
[MAXTIME (number)]
[NAMESERVER (DNRNSCxx)]
[NETWORK (DNRNETxx)]
[NETWORKPREF (DNRNPCxx)]
[PROTOCOL (DNRPRTxx)]
[QUERYWAIT (number)]
[RECURSIVE | NONRECURSIVE]
[RPCNAMES (DNRRPCxx)]
[SEARCHLIST (DNRSLCxx)]
[SERVICES (DNRSVCxx)]
[TRACE | NOTRACE]
Syntax Description
Controlling DNR Member Processing
If a secondary configuration member is not to be processed during DNR task group initialization, specify the member name NONE in the appropriate parameter.
If the local host configuration member is not to be processed at startup, specify this command:
HOSTTABLE(NONE)
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DNRCFGxx Examples
This example shows the usage of the DNRCFGxx member:
*---------------------------------------------------------------** SPECIFY POOL CONFIGURATION PARAMETERS*---------------------------------------------------------------*POOLDEF NAME ( DSRB )INITIAL ( 16 )MINIMUM ( 24 )EXPAND ( 8 )*---------------------------------------------------------------** SPECIFY DNR START UP PARAMETERS*---------------------------------------------------------------*DNR APISUBSYS(****)NAMESERVER ( NONE )ALIAS ( DNRALC00 )SEARCHLIST ( DNRSLC00 )NETWORKPREF ( DNRNPC00 )HOSTTABLE ( DNRHST00 )NETWORK ( DNRNET00 )PROTOCOL ( DNRPRT00 )SERVICES ( DNRSVC00 )RPCNAMES ( DNRRPC00 )CYCLEMAX ( 04 )QUERYWAIT ( 06 )MAXSENDS ( 05 )NONRECURSIVENOTRACENOINTERNALTRACEThis example shows DNRCFGxx in GLOBAL mode. Note that the suffix GL is used to indicate use of GLOBAL mode.
*=================================================**SPECIFY POOL CONFIGURATION PARAMETERS*=================================================*POOLDEF NAME ( DSRB )INITIAL ( 16 )MINIMUM ( 24 )EXPAND ( 8 )*=================================================**SPECIFY DNR START UP PARAMETERS*RPCNAMES ( DNRRPC00 )*=================================================*DNR APISUBSYS ( **** )NAMESERVER ( DNRNSCGL )ALIAS ( DNRALCGL )SEARCHLIST ( DNRSLCGL )NETWORKPREF ( DNRNPCGL )HOSTTABLE ( DNRHSTGL )NETWORK ( DNRNETGL )PROTOCOL ( DNRPRT00 )SERVICES ( DNRSVC00 )CYCLEMAX ( 04 )QUERYWAIT ( 03 )MAXSENDS ( 03 )MAXTIME ( 90 )RECURSIVETRACEINTERNALTRACERecommendations
It is recommended that you always set APISUBSYS (****) so that the subsystem is always associated with the Cisco IOS for S/390 job.
It is recommended that you set the parameter INTERNALTRACE on the DNR statement.
You must specify the RECURSIVE parameter on a local network utilizing firewalls in GLOBAL mode. The RECURSIVE parameter directs DNR to only use the name servers in its name server list (in file DNRNSCxx). The NONRECURSIVE parameter directs DNR to use other name servers as it learns about them. In a firewall environment, DNR sends out queries to other servers that cannot be answered. Running DNR in GLOBAL mode with the NONRECURSIVE parameter set generates increasing amounts of superfluous network activity as DNS learns about other name servers beyond the local firewall.
If you are having problems resolving host names, turn on the TRACE parameter on the DNR statement.
All entries in member DNRCFGxx must have sequence numbers or all the sequence numbers must be blank. Mixed sequence numbers and blanks lead to configuration parsing errors.
This example shows DNRCFGxx in LOCAL mode. The suffix LC is used to indicate the use of LOCAL mode.
*=================================================** SPECIFY POOL CONFIGURATION PARAMETERS*=================================================*POOLDEF NAME ( DSRB )INITIAL ( 16 )MINIMUM ( 24 )EXPAND ( 8 )*=================================================** SPECIFY DNR START UP PARAMETERS*=================================================*DNR APISUBSYS ( **** )ALIAS ( DNRALCLC )SEARCHLIST ( DNRSLCLC )NAMESERVER ( NONE )NETWORKPREF ( DNRNPCLC )HOSTTABLE ( DNRHSTLC )NETWORK ( DNRNETLC )CYCLEMAX ( 03 )QUERYWAIT ( 2 )MAXSENDS ( 10 )MAXTIME ( 90 )RECURSIVETRACEINTERNALTRACEIn local mode, all hosts will be resolved from the files DNRALCxx and DNRHSTxx.
NAMESERVER(NONE) on the DNR statement indicates that there is no domain name server in the network to resolve host names.
It is recommended that you turn on INTERNALTRACE on the DNR statement.
If you are having problems resolving host names, turn on the TRACE parameter on the DNR statement.
All entries in file DNRCFGxx must have sequence numbers or all the sequence numbers must be blank. Mixed sequence numbers and blanks lead to configuration parsing errors.
Secondary DNR Members
DNR uses nine secondary configuration members that are referenced from within the DNRCFGxx member. These members provide directory information that enables DNR to satisfy or aid in processing application program requests. At system startup, these members are read and customization data is stored for processing by the DNR. If any of these members are changed, the DNR task group must be stopped and restarted for the new changes to take effect.
The DNR configuration members are 80-character members consisting of fields separated by spaces. Entries that require more than one line can be extended by entering a special character sequence. A dash (-) placed at the end of a line indicates the next field continues on the next line. A plus sign (+) placed at the end of a line indicates the field continues on the next line.
The address:
OUR.COM. A.OUR.COM. 26.26.26.26 may be entered as:OUR.COMA.OUR.COM. 26.26.26.26OUR.COM. A.OUR. +COM. 26.26.26.26Mapping Host Names (DNRHSTxx)
The DNRHSTxx member in the PARM data set implements a static host table. It is referenced by the HOSTTABLE parameter of the DNR statement in DNRCFGxx. This member satisfies
Cisco IOS for S/390 and its API requests to resolve fully qualified domain names to Internet addresses. Use DNRHSTxx for LOCAL requests and as a backup for GLOBAL requests. Configure DNRHSTxx with the fully qualified names and Internet addresses of hosts at your site.
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The format of the DNRHSTxx member shows the host domain name followed by the host address in dotted decimal format:
CETI.OUR.COM. 129.192.192.235IBM.OUR.COM. 129.192.192.111IBM.OUR.COM. 129.192.192.112Host names must end with a period (.) for proper name resolution. Host names are used in local mode.
Host Name Syntax
hostname hostaddress comment
Syntax Description
DNRHSTxx Example
This example shows the usage of the host name:
LOOPBACK.OUR.COM. 127.0.0.1 TCP/IP LOOPBACK ADDRESSA.OUR.COM. 192.16.73.1A.OUR.COM. 192.16.73.2LOCALHOST. 127.0.0.1NIC.DDN.MIL. 192.67.67.20A.OUR.COM. 192.16.73.1B.OUR.COM. 192.16.73.2Configuring the DNRHSTxx member enables the DNR to satisfy all LOCAL host name to Internet address requests given the fully qualified domain name listed in the host domain name field of the DNRHSTxx member.
This file must contain, at a minimum:
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If you have DNR configured in GLOBAL mode, this member must also contain the fully qualified names of the Domain Name Servers in the network.
If a site's DNRHSTxx configuration member includes the items listed in the previous distributed DNRHST00 member list, and a Cisco IOS for S/390 user attempts to establish an FTP session with B.OUR.COM and Cisco IOS for S/390 is configured in LOCAL mode, DNR returns 192.16.73.2 as the address to Cisco IOS for S/390, enabling the connection to be established.
Alternatively, you can specify partially qualified names instead of fully qualified names.
You can establish an FTP session to B.OUR.COM. by specifying a partially qualified host name such as B.
In order to specify a host name other than the fully qualified name given in the host domain name field of the DNRHSTxx member, the DNRALCxx member and/or the DNRSLCxx member must be configured. DNRALCxx and/or DNRSLCxx members must be configured regardless of GLOBAL or LOCAL requests.
GLOBAL Example
This example shows DNRHSTxx in GLOBAL mode:
MVS.SITE1.COM. 138.22.140.117MVS. 138.22.140.117ACSS. 138.22.140.117SUN2.SITE1.COM. 138.22.140.44SUN2. 138.22.140.44LOOPBACK.SITE1.COM. 127.0.0.1LOOPBACK. 127.0.0.1For each host, place two mappings into the file:
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Map the subsystem name ending with a period map to an IP address.
The only hosts needed in global are the MVS Cisco IOS for S/390 host, loopback, and the domain name server host.
All entries in file DNRHSTxx must have sequence numbers or all the sequence numbers must be blank. Mixed sequence numbers and blanks lead to configuration parsing errors.
LOCAL Example
This example shows DNRHSTxx in LOCAL mode:
MVS.SITE1.COM. 138.22.140.117MVS. 138.22.140.117ACSS. 138.22.140.117MVS1.SITE1.COM. 138.22.140.13MVS1. 138.22.140.13MVS3.SITE1.COM. 138.22.140.136MVS3. 138.22.140.136SUN2.SITE1.COM. 138.22.140.165SUN2. 138.22.140.165SUN1.SITE1.COM. 138.22.140.165SUN1. 138.22.140.165OLDSUN.SITE1.COM. 138.22.140.160OLDSUN. 138.22.140.160SUNHQ.SITE1.COM. 138.22.140.128SUNHQ. 138.22.140.128LOOPBACK.SITE1.COM. 127.0.0.1LOOPBACK. 127.0.0.1For each host, place two mappings into the file.
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Map the subsystem name ending with a period to an IP address.
Note
You can still get to a host by using an IP address that is not in files DNRALCxx and DNRHSTxx.
All entries in file DNRHSTxx must have sequence numbers or all the sequence numbers must be blank. Mixed sequence numbers and blanks lead to configuration parsing errors.
Host Name Aliases (DNRALCxx)
The DNRALCxx member in the PARM data set creates fully qualified domain names from partially qualified domain names. It is referenced by the ALIAS parameter of the DNR statement in DNRCFGxx. This member must be configured with the fully qualified domain name of the Cisco IOS for S/390 subsystem name. This member must also be configured in conjunction with the DNRSLCxx member to enable Cisco IOS for S/390 users to specify partially qualified domain names (not ending in a period) as arguments to DNR requests that require a fully qualified domain name as a search argument. Configure DNRALCxx with site specific information.
DNRALCxx Format
The member format of the DNRALCxx member is
The format of the DNRALC00 member distributed with Cisco IOS for S/390 is shown below:
Specify at least one alias entry for each copy of Cisco IOS for S/390 running at your site. The entry must have the Cisco IOS for S/390 Subsystem Name mapped to the fully qualified host name
(in other words, ACSS A.OUR.COM).The alias configuration member, DNRALCxx, works very closely with the search list configuration member (DNRSLCxx).
Note
You must specify an alias entry that maps the Cisco IOS for S/390 subsystem ID to the host name; the replacement string must end in a period. Failure to do this will cause certain tasks to terminate (in other words, USMTP) and also causes the SNM task group to fail.
Search String Syntax
search_string replacement_string comment
Syntax Description
Host Aliases Examples
In these examples:
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This example shows the usage of the host aliases:
ACSS A.OUR.COM. TCP/IP SUBSYSTEM NAMEMVS A.OUR.COM. AN ALIAS FOR OUR LOCAL HOSTLOOPBACK LOOPBACK.OUR.COM. TCP/IP LOOPBACKA A.OUR.COM. ALIAS TO AVOID SEARCHLISTThis entry in the DNRALCxx configuration member lets users connect to A.OUR.COM by ACSS:
ACSS A.OUR.COM.GLOBAL Mode Example
This example shows DNRALCxx configured in GLOBAL mode:
ACSS MVS. SITE1.COM.MVS MVS.SITE1.COM.HOBBES HOBBES.SITE1.COM.LOOPBACK 127.0.0.1LOCALHOST 127.0.0.1LOCAL Mode Example
This example shows DNRALCxx in LOCAL mode:
ACSS MVS.SITE1.COM.MVS MVS.SITE1.COM.MVSHQ MVSHQ.SITE1.COM.SUN1 SUN1.SITE1.COM.SUN2 SUN2.SITE1.COM.LOOPBACK 127.0.0.1 TCP/IP LOCAL HOST NAMELOCALHOST 127.0.0.1 TCP/IP LOCAL HOST NAMESearch Lists (DNRSLCxx)
Use the DNRSLCxx member to specify the search list for the DNR component of Cisco IOS for S/390. This member name is referenced as the argument in the SEARCHLIST operand of the DNR statement in the DNRCFGxx member.
The DNRSLCxx member in the PARM data set creates fully qualified domain names from partially qualified domain names. Configure this member in conjunction with the DNRALCxx member to enable Cisco IOS for S/390 users to specify partially qualified domain names (not ending in a period) as arguments to DNR requests that require a fully qualified domain name as a search argument. Configure DNRSLCxx with site-specific information.
The domain field must end in a period (.).
Search List Syntax
domain_name comment
Syntax Description
DNRSLCxx Usage
This table shows the format of the DNRSLCxx member:
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Try root first,
OUR.COM.
...then OUR.COM,
ISI.EDU.
...then try this.
The format of the default DNRSLC00 member distributed with Cisco IOS for S/390 is shown here:
OUR.COM. <=== Place your domain here.. Put root level next.On receipt of a partially qualified name, the DNR must be able to search the directory and create a fully qualified domain name whether the request is LOCAL or GLOBAL. The DNRSLCxx member information is used with the Cisco IOS for S/390 subsystem name configured in the DNRALCxx member to build a search list.
If the DNRSLCxx at your site contains this entry:
THEIR.COM.MY.EDU.And your DNRALCxx contains this entry:
ACSS A.OUR.COMDNR creates this search list:
THEIR.COM.MY.EDU.OUR.COM..On receipt of a partial domain name, DNR concatenates the partial name with each item in the search list and searches the directory for the qualified names. It performs a check for string uniqueness, making it possible to reorder the local host domain search by adding a level to the search list.
If the site DNRSLCxx contains this entry:
OUR.COM..THEIR.COM.MY.EDU.And your DNRALCxx contains this entry:
ACSSA.OUR.COMDNR creates this search list:
OUR.COM..THEIR.COM.MY.EDU.COM.List the local domain followed by the root domain (.) first in the site DNRSLCxx.
All entries in file DNRSLCxx must have sequence numbers or all the sequence numbers must be blank. Mixed sequence numbers and blanks lead to configuration parsing errors.
Search List Examples
Here is an example of DNRSLCxx. The configuration for both GLOBAL and LOCAL is the same:
SITE1.COM.COM.. ROOTThe first line contains your local domain name SITE1.COM. ending with a period.
The second line contains the last qualifier of your domain name COM. ending with a period.
The third line contains the last qualifier, which is a period (.)
Coordinating DNRALCxx and DNRSLCxx Configuration
As stated, the purpose of DNRALCxx and DNRSLCxx configuration files is to enable Cisco IOS for S/390 users to specify partially qualified domain names as arguments to DNR requests that require a fully qualified domain name as a search argument. Without the DNRALCxx and DNRSLCxx configuration files, Cisco IOS for S/390 itself and its users would be required to specify fully qualified domain names as arguments to DNR requests that require fully qualified domain names. Configuration of these files, however, enables DNR users to request information giving partially qualified names.
When the DNR receives a partially qualified name, it must be able to search the directory and create a fully qualified domain name whether the request is LOCAL or GLOBAL. A minimum configuration maps your Cisco IOS for S/390 subsystem name to the Cisco IOS for S/390 legal fully qualified host name in the DNRALCxx member. This enables your site to resolve all names within your domain by giving the host name as a partially qualified name.
If your DNRALCxx configuration member contains the entry:
ACSS A.OUR.COM.and your DNRSLCxx configuration contains this entry
OUR.COM.COM..Cisco IOS for S/390 users are able to connect to A.OUR.COM. by specifying either A, A.OUR, or A.OUR.COM partially qualified names.
The DNR is able to resolve all names within the local domain (OUR.COM. in the previous example) if the DNRALCxx member includes the proper subsystem name configuration.
To connect to domains other than the local domain without having to specify a fully qualified name, configure DNRSLCxx with the remote domain.
To enable Telnet users to connect to C.THEIR.COM. by specifying C, configure DNRSLCxx with this entry:
THEIR.COM.Alternatively, a site may list the specific alias in the DNRALCxx member this way:
C C.THEIR.COM.However, the entry in DNRALCxx in this example lets DNR resolve C to C.THEIR.COM. only. Entering THEIR.COM in the search list lets Cisco IOS for S/390 users resolve all names within the THEIR.COM. domain specifying the host label only.
DNR Alias and Search List Recommendations
Here are some recommendations for configuring the DNRALCxx and DNRSLCxx members:
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If DNRALCxx is configured with these entries:
A MVSMVS A.OUR.COM.A request for A resolves to MVS only. If an application program wants a recursive search, it must be included in the application program. Likewise, the search returns only one replacement string; therefore, the search string must be unique. However, several search strings can have the same replacement string.
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Name Servers (DNRNSCxx)
Use the DNRNSCxx member to specify the name servers assigned various domains for the DNR component of Cisco IOS for S/390. This member name is referenced as the argument in the NAMESERVER operand of the DNR statement in the DNRCFGxx member.
This member must contain site specific information if Cisco IOS for S/390 is configured in GLOBAL mode or if any API application programs issue GLOBAL requests. If running in LOCAL mode, specify NAMESERVER(NONE) in DNRCFGxx to ensure usage of LOCAL tables.
The domain and nameserver fields must end in a period (.).
Name Server Syntax
domain nameserver nsiaddr comment
Syntax Description
DNRNSCxx Operation
Table 7-2 shows the format of the DNRNSCxx member:
Table 7-2
DNRNSXxx member
Here is the format of the DNRNSC00 member distributed with Cisco IOS for S/390:
Here is an example of DNRNSCxx configured for GLOBAL mode:
IN-ADDR.ARPA. SUNSERVER.SITE1.COM. 138.22.140.44SITE1.COM. SUNSERVER.SITE1.COM. 138.22.140.44. NS.NIC.DDN.MIL. 192.67.67.53138.22.140.44 is the local network domain resolver host.
The first line must contain IN-ADDR.ARPA. going to your local domain network server host (ending with a period) followed by its IP address.
The second line must contain an installation's domain name (colmbia.com.) (ending with a period) going to your local domain network server host (ending with a period) followed by its IP address.
192.67.67.53 is the DDN network domain resolver host.
The third line goes out to the NIC to resolve remote hosts.
If an installation has no Internet connection, or if there is a firewall that prevents DNR query responses from returning, then the third line would look like (except the period would start in column 1):
. SUNSERVER.SITE1.COM. 138.22.140.44All entries in file DNRNSCxx must have sequence numbers or all the sequence numbers must be blank. Mixed sequence numbers and blanks lead to configuration parsing errors.
On receipt of an application program request, the DNR builds a list of name servers to query for each outgoing request. This list is built by choosing the "closest" name servers for a particular domain name. The "closest" name server is determined by matching the domain of the search string provided in the application program request and the domains indicated in this member. This list is then sorted according to the networks specified in the DNRNPCxx configuration member described here. If running in LOCAL mode, specify NAMESERVER(NONE) in DNRCFGxx to ensure the use of local tables; this is the default as shipped in DNRCFGxx.
When queries are sent to name servers, a name server may return an address of a name server that is closer to the requested domain. These name server "delegation" records are added to the cache maintained by the DNR and are used for subsequent queries. Therefore, the DNRNSCxx member contains a list of name servers to be used on initial queries so long as delegations are not received.
If this member is empty, all GLOBAL requests are processed as if they were requested with the LOCAL option.
For reliability reasons, include the name servers for the local host's domain and two root name servers in this member. Also, the local host's domain name server should be attached to the local subnetwork.
To use a local name server (instead of a networked name server) to resolve addresses, specify the local name server in the DNRNSCxx member. (This may be particularly important for networks protected by a "fire wall", in which case name server queries may not be able to be returned to your local DNR server). It is also recommended that reverse address lookup (IN-ADDR.ARPA) is used.
DNRNSCxx member format:
IN-ADDR.ARPA. SERVERA.OUR.COM. 192.16.43.4OUR.COM. SERVERA.OUR.COM. 192.16.43.4IN-ADDR.ARPA. SERVERB.OUR.COM. 192.16.73.3OUR.COM. SERVERB.OUR.COM. 192.16.73.3Name Servers Example
This example shows the usage of the name servers:
. NIC.DDN.MIL. 26.0.0.73 ROOT NAME SERVER. NIC.DDN.MIL. 10.0.0.51 ROOT NAME SERVER. A.ISI.EDU. 26.3.0.13 ROOT NAME SERVERSetting Network Preferences (DNRNPCxx)
The DNRNPCxx member in the PARM data set is used to order the preferred routes of networks. It is referenced by the NETWORKPREF parameter of the DNR statement in DNRCFGxx. This member, used by the DNR, affects the order of name servers that are queried. The list is also used to order returned address lists when a remote host is multi-homed. This member must contain site specific information if Cisco IOS for S/390 is configured in GLOBAL mode or if any Cisco IOS for S/390 application programs issue GLOBAL requests.
Network Preferences Syntax
network comment
network
Specifies a network address in dotted decimal notation.
Default: None
comment
Specifies an optional comment.
Default: None
Syntax Description
DNRNPCxx Configuration
Table 7-3 shows the member format of the DNRNPCxx member:
Table 7-3 DNRNPCxx member
The DNRNPC00 member distributed with Cisco IOS for S/390 is shown below. The configuration is the same for both GLOBAL or LOCAL mode:
192.16.73 PUT THE LOCAL NETWORK FIRST,192.67.67 ... THEN NIC.DDN.MIL NETWORK,26 ... THEN MILNET,10 ... THEN ARPANET.The NICDDN, ARPANET, and MILNET entries (lines 2-4) can be placed in file DNRNETxx to resolve other hosts on the Internet.
Note
If your installation has a firewall that will not allow DNR query responses back into the installation, do not place these lines (2-4) in this file.
All entries in file DNRNETxx must have sequence numbers or all the sequence numbers must be blank. Mixed sequence numbers and blanks lead to configuration parsing errors.
Network Preference Example
This example shows the usage of the network preference:
192.16.73 PUT OUR LOCAL NETWORK FIRST26 THEN MILNETSetting Network Name to Network Number Mapping (DNRNETxx)
The DNRNETxx member in the PARM data set specifies network name to network number mappings and vice versa. It is referenced by the NETWORK parameter of the DNR statement in DNRCFGxx. Configuration of this member is required only for sites that run Cisco IOS for S/390 application programs that issue DIRSRV GET NETWORK requests.
Network Syntax
networkname networkaddress comment
Syntax Description
Table Table 7-4 shows the member format of the DNRNETxx member:
Table 7-4 DNRNETxx member
The DNRNET00 member distributed with Cisco IOS for S/390 is shown below:
ARPANET 10MILNET 26LOCALNET 192.16.73 LOCAL HOST NETWORK.Here is an example of DNRNETxx configured for either LOCAL or GLOBAL mode:
ETHERNET2 138.22.140 LOCAL HOST NETWORKNICDDN 192.67 OPTIONAL LINE WHEN CONNECTED TO THE INTERNETARPANET 10 OPTIONAL LINE WHEN CONNECTED TO THE INTERNETMILNET 26 OPTIONAL LINE WHEN CONNECTED TO THE INTERNET138.22.140 is our local network.
The NICDDN, ARPANET, and MILNET entries (lines 2-4) can be placed in file DNRNETxx to resolve other hosts on the Internet.
Note
If your installation has a firewall that will not allow DNR query responses back into the installation, do not place these lines (2-4) in this file.
All entries in file DNRNETxx must have sequence numbers or all the sequence numbers must be blank. Mixed sequence numbers and blanks lead to configuration parsing errors.
Network Names Examples
This example shows the usage of the network names:
ARPANET 10MILNET 26LOCALNET 192.16.73 LOCAL HOST'S NETWORKSetting Protocol Name to Address Mappings (DNRPRTxx)
The DNRPRTxx member of the PARM data set specifies protocol name to address mappings and vice versa. It is referenced by the PROTOCOL parameter of the DNR statement in DNRCFGxx. Configuration of this member is required only for sites that run Cisco IOS for S/390 application programs that issue DIRSRV GET PROTOCOL requests.
Protocol Name Syntax
protocolname protocolnumber comment
Syntax Description
Table 7-5 shows the member format of the DNRPRTxx member:
Table 7-5
DNRPRTxx member
This table shows the DNRPRT00 member distributed with Cisco IOS for S/390:
ICMP 1 # INTERNET CONTROL MESSAGE PROTOCOL.GGP 3 # GATEWAY-GATEWAY PROTOCOL.TCP 6 # TRANSMISSION CONTROL PROTOCOL.EGP 8 # EXTERIOR GATEWAY PROTOCOL.PUP 12 # PARC UNIVERSAL PACKET PROTOCOL.UDP 17 # USER DATAGRAM PROTOCOL.HMP 20 # HOST MONITORING PROTOCOL.XNS-IDP 22 # XEROX NS IDP.RDP 27 # "RELIABLE DATAGRAM" PROTOCOL.Protocol Names Example
This example shows the usage of the protocol names:
TCP 6 TRANSMISSION CONTROL PROTOCOLUDP 17 USER DATAGRAM PROTOCOLSetting Protocol Name/Service Pair to Port Numbers (DNRSVCxx)
The DNRSVCxx member in the PARM data set is used to specify the mappings from protocol name/service name pairs to port numbers and vice versa. It is referenced by the SERVICES parameter of the DNR statement in DNRCFGxx. Configuration of this member is required only for sites that run Cisco IOS for S/390 application programs that issue DIRSRV GET SERVICE requests. This is a static table.
Protocol Name/Service Pair Syntax
protocol service portnumber comment
Syntax Description
DNRSVCxx Configuration
Table 7-6 shows the format of the DNRSVCxx member:
Table 7-6
TCP
FTP
21
FILE TRANSFER PROTOCOL
TCP
SMTP
25
SIMPLE MAIL TRANSFER
UDP
SMTP
25
SIMPLE MAIL TRANSFER
DNRSVCxx member
The DNRSVC00 member distributed with Cisco IOS for S/390 is shown below:
TCP ECHO 7TCP DISCARD 9 SINK NULLTCP SYSTAT 11 USERSTCP DAYTIME 13TCP NETSTAT 15TCP QOTD 17 QUOTETCP CHARGEN 19 TTYTST SOURCETCP FTP 21TCP TELNET 23TCP SMTP 25 MAILTCP TIME 37 TIMSERVERTCP NAMESERVER 42 NAME # len 116TCP WHOIS 43 NICNAMETCP DOMAIN 53 NAMESERVER # Domain Name ServerTCP MTP 57 # DeprecatedTCP RJE 77 NETRJSTCP FINGER 79TCP LINK 87 TTYLINKTCP SUPDUP 95TCP HOSTNAMES 101 HOSTNAME # Usually fromTCP POP 109 POSTOFFICETCP SUNRPC 111TCP AUTH 113 AUTHENTICATIONTCP SFTP 115TCP UUCP-PATH 117TCP NNTP 119 READNEWS UNTP # Usenet news transferTCP EXEC 512TCP LOGIN 513TCP SHELL 514 CMD # No passwordsTCP PRINTER 515 SPOOLER # Line printerTCP EFS 520 # For LucasFilmTCP TEMPO 526 NEWDATETCP COURIER 530 RPCTCP CONFERENCE 531 CHATTCP NETNEWS 532 READNEWSTCP UUCP 540 UUCPD # UUCP DaemonTCP REMOTEFS 556 RFS_SERVER RFS # Brunhoff remote filesyTCP UUCP 540 UUCPD # UUCP DaemonTCP REMOTEFS 556 RFS_SERVER RFS # Brunhoff remote filesyTCP VMTELNET 1023UDP ECHO 7UDP DISCARD 9 SINK NULLUDP DAYTIME 13UDP CHARGEN 19 TTYTST SOURCEUDP TIME 37 TIMSERVERUDP RLP 39 RESOURCE # Resource locatorUDP DOMAIN 53 NAMESERVERUDP TFTP 69UDP SUNRPC 111UDP SNMP 161 # SNMPDUDP BIFF 512 COMSATUDP WHO 513 WHODUDP SYSLOG 514UDP TALK 517UDP NTALK 518UDP ROUTE 520 ROUTER ROUTED # RIPUDP TIMED 525 TIMESERVERUDP NETWALL 533 # Emergency BroadcastService Names Example
This example shows the usage of the service names:
TCP FTP 21 FILE TRANSFER PROTOCOLTCP SMTP 25UDP RPC 111Setting RPC Name-to-Program Mappings (DNRRPCxx)
The DNRRPCxx member in the PARM data set is used to specify RPC name to RPC program number mappings and vice versa. It is referenced by the RPCNAMES parameter of the DNR statement in DNRCFGxx. The file also includes RPC alias to RPC official name mappings. Configuration of this member is required only for sites that run Cisco IOS for S/390 application programs that issue DIRSRV GET RPC requests such as NFS. This is a static table.
RPC Name-to-Program Mappings Syntax
RPC_name RPC_number RPC_alias comment
Syntax Description
Table 7-7 shows the member format of the DNRRPCxx member. An RPC name may have a maximum of 5 aliases:
Table 7-7
PORTMAPPER
100000
PORTMAP SUNRPC
RSTATD
100001
RSTAT RSTAT_SVC RUP
PERFMETER
RUSERSD
100002
RUSERS
NFS
100003
NFSPROG
DNRRPCxx member
The DNRRPC00 member distributed with Cisco IOS for S/390 is shown below.
Note
PORTMAPPER 100000 PORTMAP SUNRPCRSTATD 100001 RSTAT RSTAT_SVC RUP PERFMETERRUSERSD 100002 RUSERSNFS 100003 NFSPROGYPSERV 100004 YPPROGMOUNTD 100005 MOUNT SHOWMOUNTYPBIND 100007WALLD 100008 RWALL SHUTDOWNYPPASSWDD 100009 YPPASSWDETHERSTATD 100010 ETHERSTATRQUOTAD 100011 RQUOTAPROG QUOTA RQUOTASPRAYD 100012 SPRAY3270_MAPPER 100013RJE_MAPPER 100014SELECTION_SVC 100015 SELNSVCDATABASE_SVC 100016REXD 100017 REXALIS 100018SCHED 100019LLOCKMGR 100020NLOCKMGR 100021X25.INR 100022STATMON 100023STATUS 100024BOOTPARAM 100026YPUPDATED 100028 YPUPDATEKEYSERV 100029 KEYSERVERTFSD 100037NSED 100038NSEMNTD 100039MVSMOUNT 100044SHOWATTR 100059PCNFSD 150001RPC Name Example
This example shows the usage of the RPC name:
PORTMAPPER 100000 PORTMAP SUNRPCRSTATD 100001 RSTAT RSTAT_SVC RUP PERFMETERRUSERSD 100002 RUSERSNFS 100003 NFSPROGYPSERV 100004 YPPROGMOUNTD 100005 MOUNT SHOWMOUNTYPBIND 100007WALLD 100008 RWALL SHUTDOWNYPPASSWDD 100009 YPPASSWDExamples of DNR Customization
This section provides examples of DNR configurations. These examples demonstrate how the DNR task group can be customized to meet the specific needs of your installation.
DNR with Only Configuration Data
This section uses an example company named XYZ, Inc., that has a single Ethernet. Connected to the Ethernet is an MVS system running Cisco IOS for S/390 and several workstations. The Ethernet is not connected to another network. Therefore, the network administrator randomly chose an internet network number of 1.0.0.0. The GLOBAL statement DNR operand in APPCFGxx must specify LOCAL for this configuration.
New PARM member DNRHST01
The network administrator assigns the MVS system the internet address of 1.0.0.1. Each workstation is assigned the next available host number (in other words 1.0.0.2, 1.0.0.3,...). Lastly, the MVS system is given the host name MVS and the workstations are assigned the names of their users.
A new host configuration member, DNRHST01, is created listing the host names and internet addresses of the MVS system and workstations. Note that each host name ends with a period:
LOOPBACK. 127.0.0.1 Required EntryMVS. 1.0.0.1 TCP/IP HOSTBILL. 1.0.0.2JOE. 1.0.0.3ROBERT. 1.0.0.5KIRK. 1.0.0.6MARY. 1.0.0.7SAM. 1.0.0.8FRANK. 1.0.0.9DEBBIE. 1.0.0.10NAT. 1.0.0.11BARB. 1.0.0.12ALICE. 1.0.0.13CHARLIE. 1.0.0.14New PARM member DNRALC01
One of the workstation users, Robert, is known by both his formal name and by the nickname Bob. A new alias configuration member, DNRALC01, is created to assign an alias for Robert. In addition to the alias for Bob, there is a required alias entry to map the Cisco IOS for S/390 subsystem name to the Cisco IOS for S/390 host name. An entry to map ACSS to MVS is included in DNRALC01.
ACSS MVS. TCP/IP SUBSYSTEM NAMEBOB ROBERT. ALIAS BOB FOR HOST NAME ROBERTNew TCPPARM member DNRSLC01
A new search list member, DNRSLC01, is created. Without this member, users must enter the fully qualified host names are listed in the DNRHST01 member. A single entry, a period (.), is included to enable users to specify host names as partially qualified names (not including the trailing period). Therefore, if the host name MARY is entered, the period is appended to the end forming the host name MARY. which is in the DNRHST01 member.
.ADD PERIOD IF OMITTEDNew PARM member DNRCFG01
To ensure that all requests are processed in LOCAL mode the NAMESERVER parameter of the DNR statement is updated to specify NONE.
The primary configuration member must be modified to include the new secondary configuration members. A new DNRCFG01 member is created using DNRCFG00 as a model. DNRCFG01 includes the new secondary members. Note that only the NAMESERVER, ALIAS, SEARCHLIST and HOSTTABLE keywords are modified.
*=================================================**SPECIFY POOL CONFIGURATION PARAMETERS*=================================================*POOLDEF NAME ( DSRB )INITIAL ( 16 )MINIMUM ( 24 )EXPAND ( 8 )*=================================================**SPECIFY DNR START UP PARAMETERS*=================================================*DNR APISUBSYS ( **** )NAMESERVER ( NONE )ALIAS ( DNRALC01 )SEARCHLIST ( DNRSLC01 )NETWORKPREF ( DNRNPC00 )HOSTTABLE ( DNRHST01 )NETWORK ( DNRNET00 )PROTOCOL ( DNRPRT00 )SERVICES ( DNRSVC00 )CYCLEMAX ( 04 )QUERYWAIT ( 3 )MAXSENDS ( 05 )RECURSIVENOTRACENOINTERNALTRACENew PARM member START01
The start command for the DNR task group includes the new DNRCFG01 member. A new PARM data set member, START01, is created using the START00 member as the model. The START DNR statement is modified to specify DNRCFG01 as the new primary configuration member.
START APISTART ACPSTART DNR CNFG(01)START MAPSTART SNMFinally, the JCL procedure to run Cisco IOS for S/390 replaces the CMND=START00 keyword of the PROC statement with CMND=START01. This invokes the new PARM member START01 when Cisco IOS for S/390 begins.
Migration of DNR to DNS
UVW, Inc. has a single Ethernet. Connected to the Ethernet is an MVS system running
Cisco IOS for S/390 and several workstations. This Ethernet is attached to the Internet via a single IP router. The Ethernet was assigned the class C internet address 192.3.17.0. Also, an official domain name of UVW.COM. has been assigned UVW.The network administrator assigned the MVS system the internet address of 192.3.17.1. Each workstation was assigned the next available host number (in other words, 192.3.17.2, 192.3.17.3,...). Lastly, the MVS system was given the host name MVS.UVW.COM. and the workstations were assigned the names of their user's concatenated with UVW's domain name.
The domain name server workstation and the IP router have not been purchased. However, the network administrator customized the DNR configuration members to facilitate the conversion from LOCAL to GLOBAL configuration. The GLOBAL statement DNR operand in APPCFGxx also needs to be updated from LOCAL to GLOBAL mode.
New PARM member DNRHST01
A new host configuration member, DNRHST01, is created listing the host names and internet addresses of the MVS system and workstations. Note that each host name ends with a period (.).
LOOPBACK.UVW.COM. 127.0.0.1 Required EntryMVS.UVW.COM. 192.3.17.1 TCP/IP HOSTBILL.UVW.COM. 192.3.17.2 WORKSTATIONSJOE.UVW.COM. 192.3.17.3HARRY.UVW.COM. 192.3.17.4ROBERT.UVW.COM. 192.3.17.5JOHN.UVW.COM. 192.3.17.6LINDA.UVW.COM. 192.3.17.7DON.UVW.COM. 192.3.17.8TOM.UVW.COM. 192.3.17.9ANN.UVW.COM. 192.3.17.11MARY.UVW.COM. 192.3.17.12JACKIE.UVW.COM. 192.3.17.13CHARLIE.UVW.COM. 192.3.17.14New PARM member DNRALC01
One of the workstation users, Robert, is known by both his formal name and by the nickname Bob. A new alias configuration member, DNRALC01, is created to assign an alias for ROBERT. In addition to the alias for Robert, there is a required alias entry to map the Cisco IOS for S/390 subsystem name to the host name. An entry to map ACSS to MVS.UVW.COM. is included in DNRALC01.
ACSS MVS.UVW.COM. TCP/IP SUBSYSTEM NAMEBOB ROBERT.UVW.COM. ALIAS BOB FOR HOST NAME ROBERTNew PARM member DNRSLC01
A new search list member, DNRSLC01, is created. Two entries are included to enable users to specify host names as partially qualified names (not including the trailing period). Without this member, users must enter the fully qualified host names that are listed in the DNRHST01 member. A UVW.COM. entry is included to enable users to specify host name labels. Therefore, if the host name MARY is entered, UVW.COM is appended to the end forming the host name MARY.UVW.COM., which is in the DNRHST01 member. The second entry, a period (.), is included
to enable users to specify host names without the trailing period. For example, if the host name MARY.UVW.COM is entered, the period is appended to the end forming the host name MARY.UVW.COM. which is in the DNRHST01 member.
UVW.COM..New PARM member DNRCFG01
To ensure that all requests are processed in LOCAL mode (not communicating with a name server), the NAMESERVER operand is updated to specify NONE.
The primary configuration member must be modified to include the new secondary configuration members. A new DNRCFG01 member is created using DNRCFG00 as a model. DNRCFG01 includes the new secondary members. Note that only the NAMESERVER, ALIAS, SEARCHLIST, and HOSTTABLE keywords are modified.
*=================================================**SPECIFY POOL CONFIGURATION PARAMETERS *=================================================*POOLDEF NAME ( DSRB )INITIAL ( 16 )MINIMUM ( 24 )EXPAND ( 8 )*=================================================**SPECIFY DNR START UP PARAMETERS==================================================*DNR APISUBSYS ( **** )NAMESERVER ( NONE )ALIAS ( DNRALC01 )SEARCHLIST ( DNRSLC01 )NETWORKPREF ( DNRNPC00 )HOSTTABLE ( DNRHST01 )NETWORK ( DNRNET00 )PROTOCOL ( DNRPRT00 )SERVICES ( DNRSVC00 )CYCLEMAX ( 04 )QUERYWAIT ( 3 )MAXSENDS ( 05 )RECURSIVENOTRACENOINTERNALTRACENew PARM member START01
The start command for the DNR task group must be modified to include the new DNRCFG01 member. A new PARM data set member, START01, is created using the START00 member as the model. The START DNR statement is modified to specify DNRCFG01 as the new primary configuration member.
START APISTART ACPSTART DNR CNFG ( 01 )START MAPSTART SNMFinally, the JCL procedure to run Cisco IOS for S/390 is modified to replace the CMND=START00 keyword of the PROC statement to CMND=START01. This invokes the new PARM member START01 when Cisco IOS for S/390 begins.
After several weeks of running the DNR in LOCAL mode, the domain name server workstation and IP router are purchased, installed, and configured. The domain name server is assigned the internet address of 192.3.17.100 and host name of NS.UVW.COM. The internet router is assigned the internet address of 192.3.17.101.
APPPCFG01, which is the customized copy of APPCFG00, is edited and the DNR parameter on the GLOBAL statement changed from LOCAL to GLOBAL mode. GLOBAL mode is configured by specifying a decimal value that specifies the maximum time the DNR spends processing a Cisco IOS for S/390 request.
...HOST DNR ( * 30 ) /* Global requests, 30 sec maxwait */TIMEZ ( EASTERN )LUPARM ( ACPLUPOS )SSN ( ACSS )ACBNAME ( ACCES )XSEC ( GLBLACT )JES ( 2 JES2 JES2 $ )VSREPORT...New PARM member DNRNSC01
The name server configuration member, DNRNSC01, is created indicating NS.UVW.COM. as a name server for the UVW.COM. domain. A root level domain name server is also included as a backup to the UVW.COM. name server. The NAMESERVER operand of the DNRCFG01 member must be modified from NONE to DNRNSC01.
UVW.COM.NS.UVW.COM.192.3.17.100 UVW's domain name server.A.ISI.EDU.26.3.0.13EDU domain name serverNew PARM member DNRNPC01
Multiple name servers are included in the DNRNSC01 configuration member. Therefore, a new DNRNPC01 is configured to instruct the DNR the name server order to use. A new network preference member, DNRNPC01, is created with one entry defined. This entry, 192.3.17.00, instructs the DNR to query NS.UVW.COM. first. NS.UVW.COM. is a recursive name server. A recursive name server guarantees an answer, therefore, DNRNPC01 contains only one entry.
In addition, the DNRCFG01 primary configuration member must be modified to include the new DNRNPC01 configuration member. Only the NETWORKPREF keyword is modified.
192.3.17 Our local subnet has highest preferenceDNR With Only The Domain Name System
The University of Somewhere, USW, has several Ethernets that have been in place for many years. They have participated in the Domain Name System for a long time. They have a primary and a backup domain name server to resolve requests for the USW.EDU. domain.
Recently, they upgraded their host computing system to include an IBM mainframe running MVS/ESA. Attached to this IBM host are 3270 series terminals for the students to use. Cisco IOS for S/390 is installed to enable students and faculty using the IBM system to connect to non-IBM hosts both on and off the USW campus.
The MVS system running Cisco IOS for S/390 is assigned the internet address 137.35.15.139. The primary domain name server, WISDOM.USW.EDU. is assigned the internet address 137.35.3.1. The backup domain name server, KNOWLEDGE.USW.EDU. is assigned the internet address 137.35.15.1.
New PARM member DNRALCSW:
The MVS system running Cisco IOS for S/390 is assigned the host name BIGBLUE.USW.EDU. An alias of MVSESA is also defined. A new alias member, DNRALCSW, is created. This member includes the required entry mapping the Cisco IOS for S/390 subsystem to its host name. The Cisco IOS for S/390 subsystem name is changed to USW1. DNRALCSW and includes entries for MVSESA alias and TEST.
USW1 BIGBLUE.USW.EDU. Required alias for SubsystemMVSESA BIGBLUE.USW.EDU. Alias known to studentsTEST 127.0.0.1 Alias for testing in loopback modeNew PARM member DNRSLCSW
A new search list member, DNRSLCSW, is created. Two entries are included to enable users to specify host names as a partially qualified name (not including the trailing period). Without this member, users are required to enter the fully qualified host names of all remote hosts. A UVW.EDU. entry is included to enable users to specify host name labels. The second entry, period (.), is included to enable users to specify host names without the trailing period.
USW.EDU. First try appending USW.EDU. to the name. Then try appending. to the nameNew PARM member DNRNSCSW
A new name server configuration member, DNRNSCSW, is created. The USW.EDU. name servers are included as well as two EDU. name servers.
USW.EDU. WISDOM.USW.EDU. 137.35.3.1 Primary serverUSW.EDU. KNOWLEDGE.USW.EDU. 137.35.15.1 Backup serverEDU. A.ISI.EDU. 26.3.0.103 EDU serverEDU. A.ISI.EDU. 128.9.0.107 EDU serverNew PARM member DNRNPCSW
Multiple name servers are included in the DNRNSCSW configuration member. Therefore, a new DNRNPCSW tells the DNR what name server order to use. A new network preference member, DNRNPCSW, defines three entries. The first entry, 137.35.15, instructs the DNR to query KNOWLEDGE.USW.EDU. first. The second entry, 137.35.3, instructs the DNR to query WISDOM.USW.EDU. second if KNOWLEDGE.USW.EDU. does not have an answer.
The DNRNPCSW is also used by the DNR to order returned address lists when a remote host is multihomed. The third entry, 137.35, is included to instruct the DNR to order any internet address with a network number of 137.35.0.0 after addresses with networks 137.35.15 or 137.35.3. Internet address with network numbers not included in DNRNPCSW are ordered last.
137.35.15 Our local subnet has highest preference137.35.3 This subnet is preferred also137.35 Our network takes preference above other networksNew PARM member DNRCFGSW
The primary configuration member includes the new secondary configuration members. A new DNRCFGSW member is created using DNRCFG00 as a model. DNRCFGSW includes the new secondary members. Note that only the NAMESERVER, ALIAS, SEARCHLIST, and NETWORKPREF keywords are modified.
*=================================================** SPECIFY POOL CONFIGURATION PARAMETERS *=================================================*POOLDEF NAME ( DSRB )INITIAL ( 16 )MINIMUM ( 24 )EXPAND ( 8 )*=================================================** SPECIFY DNR START UP PARAMETERS*=================================================*DNR APISUBSYS ( **** )NAMESERVER ( DNRNSCSN )ALIAS ( DNRALCSW )SEARCHLIST ( DNRSLCSW )NETWORKPREF ( DNRNPCSW )HOSTTABLE ( DNRHST00 )NETWORK ( DNRNET00 )PROTOCOL ( DNRPRT00 )SERVICES ( DNRSVC00 )CYCLEMAX ( 04 )QUERYWAIT ( 3 )MAXSENDS ( 05 )RECURSIVENOTRACENOINTERNALTRACENew PARM member STARTUSW
The start command for the DNR task group must be modified to include the new DNRCFGSW member. A new PARM data set member, STARTUSW, is created using the START00 member as the model. The START DNR statement is modified to specify DNRCFGSW as the new primary configuration member.
START APISTART ACPSTART DNR CNFG(SW)START MAPSTART SNMFinally, the JCL procedure to run Cisco IOS for S/390 is modified to replace the CMND=START00 keyword of the PROC statement to CMND=STARTUSW. This invokes the new PARM member STARTUSW when Cisco IOS for S/390 begins.
DNR Configuration Set for a Network with a Domain Name Server
This example shows a network with a router to be configured for DNR in GLOBAL mode. A complete set of sample DNR files for this configuration is included in this section. The filenames all end in WG to indicate GLOBAL.
Figure 7-1 Configuration for DNR in GLOBAL Mode
Using DNR with domain name servers (GLOBAL mode) requires that the DNR parameter be set to DNR (* timevalue) on the GLOBAL statement in file APPCFGxx.
MVS host mvs.xyz.com (IP address 136.42.50.30) exists on network xyz.com.
Host mainunix.xyz.com (IP address 136.42.50.20) acts as the primary domain name server on network xyz.com. The NONRECURSIVE parameter in file DNRCFGWG tells the MVS host to use other domain name servers as it learns about them.
Access to the internet will be via the router named router.xyz.com at IP address 136.42.50.1. While router.xyz.com is not needed in the DNR configuration files, it will be placed on a ROUTE statement in file TCPCFGxx.
Files ending with suffix 00 (for example, DNRPRT00, DNRPCC00, and DNRSVC00) are not shown because they are the same as the default distributed versions and rarely need to be updated at a site.
Sample Cisco IOS for S/390 DNR configuration files for running MVS host mvs.xyz.com with a name server on its local network are given in the following sections.
DNRALCWG
ACSS MVS.XYZ.COM.MVS MVS.XYZ.COM.MAINUNIX MAINUNIX.XYZ.COM.LOOPBACK 127.0.0.1LOCALHOST 127.0.0.1DNRCFGWG
*==========================================** SPECIFY POOL CONFIGURATION PARAMETERS*==========================================*POOLDEF NAME ( DSRB )INITIAL ( 16 )MINIMUM ( 24 )EXPAND ( 8 )*==========================================** SPECIFY DNR START UP PARAMETERS*==========================================*DNR APISUBSYS ( **** )NAMESERVER ( DNRNSCWG )ALIAS ( DNRALCWG )SEARCHLIST ( DNRSLCWG )NETWORKPREF ( DNRNPCWG )HOSTTABLE ( DNRHSTWG )NETWORK ( DNRNETWG )PROTOCOL ( DNRPRT00 )RPCNAMES ( DNRRPC00 )SERVICES ( DNRSVC00 )CYCLEMAX ( 04 )QUERYWAIT ( 03 )MAXSENDS ( 03 )MAXTIME ( 90 )NONRECURSIVETRACEINTERNALTRACEDNRHSTWG
MVS.XYZ.COM. 136.42.50.30MVS. 136.42.50.30ACSS. 136.42.50.30MAINUNIX.XYZ.COM. 136.42.50.20MAINUNIX. 136.42.50.20LOCALHOST. 127.0.0.1LOOPBACK. 127.0.0.1DNRNETWG
ETHERNET2 136.42.50 LOCAL HOST NETWORKNICDDN 192.67 OPTIONAL LINE WHEN CONNECTED TO INTERNETARPANET 10 OPTIONAL LINE WHEN CONNECTED TO INTERNETMILNET 26 OPTIONAL LINE WHEN CONNECTED TO INTERNETDNRNPCWG
136.42.50 PUT OUR LOCAL NETWORK FIRST192.67 NIC.DDN OPTIONAL INTERNET NETWORK10 THEN OPTIONAL ARPANET NETWORK26 THEN OPTIONAL MILNET NETWORKDNRNSCWG
IN-ADDR.ARPA. MAINUNIX.XYZ.COM. 136.42.50.20XYZ.COM. MAINUNIX.XYZ.COM. 136.42.50.20. MAINUNIX.XYZ.COM. 136.42.50.20. NS.NIC.DDN.MIL. 192.67.67.53DNRSLCWG
XYZ.COM.COM.. ROOTDNR Configuration Set without a Domain Name Server
This example shows a network to be configured for DNR with no domain name servers. A complete set of sample DNR files for this configuration is included in this section. The filenames all end in WL to indicate LOCAL.
Figure 7-2 Configuration for DNR with No Domain Name Servers
Using DNR without domain name servers (LOCAL mode) requires that the DNR parameter be set to LOCAL on the GLOBAL statement in file APPCFGxx.
MVS host mvs.xyz.com (IP address 136.42.50.30) exists on network xyz.com.
Since there are no name servers on the local network xyz.com, all hosts on the network should be placed in files DNRALCxx and DNRHSTxx. When running DNR in LOCAL mode there is no need to configure files DNRNETxx and DNRNSCxx. File DNRCFGWL accomplishes this by placing NETWORK(NONE) and NAMESERVER(NONE) on the DNR statement.
Access to the internet will be via the router named router.xyz.com at IP address 136.42.50.1. While router.xyz.com is not needed in the DNR configuration files, it will be placed on a ROUTE statement in file TCPCFGxx.
Files ending with suffix 00 (for example, DNRPRT00, DNRPCC00, and DNRSVC00) are not shown because they are the same as the default distributed versions and rarely need to be updated at a site.
Sample Cisco IOS for S/390 DNR configuration files for running MVS host mvs.xyz.com with a name server on its local network are given in the sections that follow.
DNRALCWL
ACSS MVS.XYZ.COM.MVS MVS.XYZ.COM.SUN SUN.XYZ.COM.PC2 PC2.XYZ.COM.MAC MAC.XYZ.COM.VM VM.XYZ.COM.UNIX2 UNIX2.XYZ.COM.MAINUNIX MAINUNIX.XYZ.COM.PC1 PC1.XYZ.COM.LOOPBACK 127.0.0.1LOCALHOST 127.0.0.1DNRCFGWL
*========================================** SPECIFY POOL CONFIGURATION PARAMETERS*========================================*POOLDEF NAME ( DSRB )INITIAL ( 16 )MINIMUM ( 24 )EXPAND ( 8 )*========================================** SPECIFY DNR START UP PARAMETERS*========================================*DNR APISUBSYS ( **** )ALIAS ( DNRALCWL )SEARCHLIST ( DNRSLCWL )NAMESERVER ( NONE )NETWORKPREF ( DNRNPCWL )HOSTTABLE ( DNRHSTWL )NETWORK ( NONE )PROTOCOL ( DNRPRT00 )RPCNAMES ( DNRRPC00 )SERVICES ( DNRSVC00 )CYCLEMAX ( 03 )QUERYWAIT ( 2 )MAXSENDS ( 10 )MAXTIME ( 90 )RECURSIVETRACEINTERNALTRACEDNRHSTWL
MVS.XYZ.COM. 136.42.50.30MVS. 136.42.50.30ACSS. 136.42.50.30SUN.XYZ.COM. 136.42.50.10SUN. 136.42.50.10PC2.XYZ.COM. 136.42.50.12PC2. 136.42.50.12MAC.XYZ.COM. 136.42.50.14MAC. 136.42.50.14VM.XYZ.COM. 136.42.50.16VM. 136.42.50.16UNIX2.XYZ.COM. 136.42.50.18UNIX2. 136.42.50.18MAINUNIX.XYZ.COM. 136.42.50.20MAINUNIX. 136.42.50.20PC1.XYZ.COM. 136.42.50.40PC1. 136.42.50.40LOCALHOST. 127.0.0.1LOOPBACK. 127.0.0.1DNRNPCWL
136.42.50 PUT OUR LOCAL NETWORK FIRST192.67 NIC.DDN OPTIONAL INTERNET NETWORK10 THEN OPTIONAL ARPANET NETWORK26 THEN OPTIONAL MILNET NETWORKDNRSLCWL
XYZ.COM.COM.. ROOTDNR Configuration Set With a Domain Name Server and a Firewall
Figure 7-3 shows a network to be configured for DNR with a domain name server and a firewall. A complete set of sample DNR files for this configuration is included in this section. The filenames all end in WF to indicate Firewall
Figure 7-3 Configuration for DNR with a Firewall
Using DNR with domain name servers (GLOBAL mode) requires that the DNR parameter be set to DNR(* timevalue) on the GLOBAL statement in file APPCFGxx.
MVS host mvs.xyz.com (IP address 136.42.50.30) exists on network xyz.com.
Host mainunix.xyz.com (IP address 136.42.50.20) acts as the only domain name server on network xyz.com. The RECURSIVE parameter in file DNRCFGWF tells the MVS host to use only domain name servers in its nameserver list (DNRNSCWF).
The RECURSIVE parameter must be set for DNR to function correctly behind a firewall.
Access to the internet will only be allowed from host mainunix.xyz.com at IP address 136.42.50.20.
Files ending with suffix 00 (for example, DNRPRT00, DNRPCC00, and DNRSVC00) are not shown because they are the same as the default distributed versions and rarely need to be updated at a site.
Sample DNR configuration files for running MVS host mvs.xyz.com with a name server on its local network behind a firewall are given below.
DNRALCWF
ACSS MVS.XYZ.COM.MVS MVS.XYZ.COM.MAINUNIX MAINUNIX.XYZ.COM.LOOPBACK 127.0.0.1LOCALHOST 127.0.0.1DNRCFGWF
*========================================** SPECIFY POOL CONFIGURATION PARAMETERS*========================================*POOLDEF NAME ( DSRB )INITIAL ( 16 )MINIMUM ( 24 )EXPAND ( 8 )*========================================** SPECIFY DNR START UP PARAMETERS*========================================*DNR APISUBSYS ( **** )NAMESERVER ( DNRNSCWF )ALIAS ( DNRALCWF )SEARCHLIST ( DNRSLCWF )NETWORKPREF ( DNRNPCWF )HOSTTABLE ( DNRHSTWF )NETWORK ( DNRNETWF )PROTOCOL ( DNRPRT00 )RPCNAMES ( DNRRPC00 )SERVICES ( DNRSVC00 )CYCLEMAX ( 04 )QUERYWAIT ( 03 )MAXSENDS ( 03 )MAXTIME ( 90 )RECURSIVETRACEINTERNALTRACEDNRHSTWF
MVS.XYZ.COM. 136.42.50.30MVS. 136.42.50.30ACSS. 136.42.50.30MAINUNIX.XYZ.COM. 136.42.50.20MAINUNIX. 136.42.50.20LOCALHOST. 127.0.0.1LOOPBACK. 127.0.0.1DNRNETWF
ETHERNET2 136.42.50 LOCAL HOST NETWORKDNRNPCWF
136.42.50 PUT OUR LOCAL NETWORK FIRSTDNRNSCWF
IN-ADDR.ARPA. MAINUNIX.XYZ.COM. 136.42.50.20XYZ.COM. MAINUNIX.XYZ.COM. 136.42.50.20. MAINUNIX.XYZ.COM. 136.42.50.20DNRSLCWF
XYZ.COM.COM.. ROOT
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