Start HOST Query (HOST)
| Where allowed to run: All environments (*ALL) Threadsafe: No |
Parameters Examples Error messages |
The Start HOST Query (STRHOSTQRY) command, or its alias HOST, is a simple utility for performing Domain Name System (DNS) lookups. It is normally used to convert names to IP addresses and vice versa.
Restrictions:
- You must have execute (*X) authority to the directories in the path of the output file.
- You must have write (*W) authority to the output file if it already exists.
- You must have read, write and execute (*RWX) authority to the output file's parent directory if the output file does not already exist.
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Parameters
| Keyword | Description | Choices | Notes |
|---|---|---|---|
| HOSTNAME | Query name | Character value | Required, Positional 1 |
| TYPE | Query type | *A, *AAAA, *ANY, *AXFR, *CNAME, *MX, *NS, *PTR, *SOA, *SRV, *TXT | Optional, Positional 2 |
| CLASS | Query class | *IN, *CH, *HS, *ANY | Optional |
| DMNNAMSVR | Domain name server | Character value, *CFG | Optional |
| SOA | Display SOA records | *NO, *YES | Optional |
| AXFR | List all hosts | *NO, *YES | Optional |
| IP6INT | Use IP6.INT domain | *NO, *YES | Optional |
| SETRDFLAG | Recursion desired | *YES, *NO | Optional |
| PROTOCOL | Network protocol | *UDP, *TCP | Optional |
| DEBUG | Show debug information | *NO, *YES | Optional |
| IPVSN | IP Version | *ALL, *IPV4ONLY, *IPV6ONLY | Optional |
| NBRDOTS | Number of dots | 0-10, 1 | Optional |
| TIMEOUT | Query timeout | 1-100, 5 | Optional |
| UDPNBRRTY | UDP retry | 0-100, 2 | Optional |
| TOSTMF | Output file | Path name, *STDOUT | Optional |
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Query name (HOSTNAME)
Specifies the name that you want the Domain Name System (DNS) server to look up. It can also be a dotted-decimal IPv4 address or a colon-delimited IPv6 address, in which case HOST will by default perform a reverse lookup for that address.
This is a required parameter.
- domain-name
- Specify a valid domain name.
- internet-address
- Specify a valid IPv4 or IPv6 address.
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Query type (TYPE)
Specifies the type of the query. The default type is *A. The list of supported query types changes with time, and not all servers support all the types that exist. This list provides some common query types for convenience and is not a complete list. If you do not see a query type you want in this list, you can still type in a character string that represents that query type. If the type is unknown by this BIND version, the query will default to an *A query with any corresponding results.
- *A
- IPv4 Address record. This is the character string 'a'.
- *AAAA
- IPv6 address record. This is the character string 'aaaa'.
- *ANY
- Any resource record. This is the character string 'any'.
- *AXFR
- Zone transfer. This is the character string 'axfr'.
- *CNAME
- Canonical name record. Returns a list of aliases for the true (canonical) host name, if any exist. This is the character string 'cname'.
- *MX
- Mail exchange record. This is the character string 'mx'.
- *NS
- Name server (DNS server) information for the zone. This is the character string 'ns'.
- *PTR
- Pointer record. Returns a name for an IP address. This is the character string 'ptr'.
- *SOA
- Start of authority record. This is the character string 'soa'.
- *SRV
- Services location selection. This is the character string 'srv'.
- *TXT
- Text record. This is the character string 'txt'.
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Query class (CLASS)
Specifies the protocol group of the information.
- *IN
- The Internet class.
- *CH
- The CHAOS class. The server provides some helpful diagnostic information through a number of built-in zones under the CHAOS class.
- version
- If your BIND server named.conf has the 'version' option configured, then you can query for it using the CHAOS class. This is the version the server should report via a query of the name 'version.bind' with type TXT, class CHAOS. The default is the real version number of this server.
HOST HOSTNAME('version.bind') TYPE(*TXT) CLASS(*CH) - hostname
- If your BIND server named.conf has the 'hostname' option configured, then you can query for it using the CHAOS class. This is the hostname the server should report via a query of the name 'hostname.bind' with type TXT, class CHAOS. This defaults to the hostname of the machine hosting the name server. The primary purpose of such queries is to identify which of a group of anycast servers is actually answering your queries.
STRHOSTQRY NAME('hostname.bind') TYPE(*TXT) CLASS(*CH) - server-id
- If your BIND server named.conf has the 'server-id' option configured, then you can query for it using the CHAOS class. This is the ID of the server should report via a query of the name 'ID.SERVER' with type TXT, class CHAOS. The primary purpose of such queries is to identify which of a group of anycast servers is actually answering your queries. The default server-id is none.
HOST HOSTNAME('ID.SERVER') TYPE(*TXT) CLASS(*CH)
- *HS
- The MIT Athena Hesiod class. Hesiod, developed by MIT Project Athena, is an information service built upon BIND. Its intent is to furnish information about users, groups, network-accessible file systems, printcaps, and mail service throughout an installation. In other words, it holds arbitrary data stored as text strings. Queries that use the HS class retrieve data stored as TXT Resource Records. You cannot specify root servers for the Hesiod class (generally the ones at MIT) in your list of root name servers.
- *ANY
- Query any class. This is a wildcard query.
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Domain name server (DMNNAMSVR)
Specifies the name or the IP address of the DNS server that HOST will use as its current server for the query session. You can specify any DNS server to which your TCP/IP network has access.
HOST retrieves information from DNS servers. It needs an active DNS server to send its queries to. If you do not specify a DNS server with DMNNAMSVR when you start the tool, it will attempt to set one of the following as its default DNS server for the session:
- DNS server your system is configured to use (*CFG), or
- The DNS server that is running on your local system.
- *CFG
- Use the DNS server that is currently designated for use by this system. These server internet addresses can be seen by prompting the Change TCP/IP Domain (CHGTCPDMN) command and looking at the values shown for the INTNETADR parameter.
- server-domain-name
- Specify the name of a DNS server.
- server-internet-address
- Specify the IP address of a DNS server.
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Display SOA records (SOA)
Specifies whether or not to print the SOA records for zone name from all the listed authoritative name servers for that zone. The list of name servers is defined by the NS records that are found for the zone.
- *NO
- Do not print SOA records.
- *YES
- Attempt to print SOA records.
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List all hosts (AXFR)
Specifies whether or not to make HOST perform a zone transfer for zone specified in the HOSTNAME parameter. A zone transfer is when all domain information in the zone is returned. HOST will display the NS, PTR and address records (A/AAAA).
- *NO
- Do not perform a zone tranfer.
- *YES
- Perform a zone transfer.
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Use IP6.INT domain (IP6INT)
Specifies whether or not to qualify the reverse lookup to be in the ip6.int zone and not the ip6.arpa zone.
- *NO
- The normal ip6.arpa zone reverse lookup will be performed.
- *YES
- An IPv6 address reverse lookup in the ip6.int zone will be performed. This zone is deprecated, but may still be required to query IPv6 backbone prefixes.
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Recursion desired (SETRDFLAG)
Specifies whether or not to set the Recursion Desired (RD) flag in the query. This should mean that the name server receiving the query will not attempt to resolve name. This enables HOST to mimic the behaviour of a name server by making non-recursive queries and expecting to receive answers to those queries that are usually referrals to other name servers.
- *YES
- Set the RD flag.
- *NO
- Do not set the RD flag.
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Network protocol (PROTOCOL)
Specified whether to use TCP or UDP when sending requests to the server.
- *UDP
- Use UDP to send the query. However, TCP will be automatically selected for queries that require it, such as zone transfer (AXFR) requests.
- *TCP
- Use TCP to send the query.
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Show debug information (DEBUG)
Specifies whether or not to turn debugging mode on. More information is displayed about the packet sent to the server and the resulting answer when debugging mode is on.
- *NO
- Turn off debugging messages.
- *YES
- Turn on debugging messages.
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IP Version (IPVSN)
Specifies whether to limit the query to IPv4 or IPv6 networks.
- *ALL
- Do not limit queries to IPv4 or IPv6.
- *IPV4ONLY
- Only send queries out IPv4 network interfaces.
- *IPV6ONLY
- Only send queries out IPv6 network interfaces.
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Number of dots (NBRDOTS)
Specifies the number of dots (period characters) that have to appear in a domain name for it to be considered absolute. Names with fewer dots are interpreted as relative names and will be searched for in the domains listed in the DMNSCHLIST parameter.
- 1
- If the domain name contains one dot it is considered an absolute name.
- 0-10
- Specify the number of dots that must be in a domain name for the domain name to be considered to be an absolute name.
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Query timeout (TIMEOUT)
Specifies the timeout interval, in seconds, to wait for a response.
- 5
- A timeout value of 5 seconds is used.
- 1-100
- Specify a valid timeout value in seconds.
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UDP retry (UDPNBRRTY)
Specifies the number of times to retry UDP queries to the current DNS server before attempting TCP queries.
- 2
- Two UDP retries will be used. This is in addition to the initial query.
- 0-100
- Specify the number of UDP retries. You normally only need to retry a query 3 to 5 times.
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Output file (TOSTMF)
Specifies the name of a stream file where all command output is written.
- *STDOUT
- All command output goes to the standard output device (normally the display).
- path-name
- Specify the path name for a stream file where output should be written.
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Examples
Example 1: Looking Up Internet Address for Domain Name
STRHOSTQRY HOSTNAME(ibm.com)
This command attempts to find information about the domain 'aol.com'. This includes A and MX records, althought the output is formatted in a different style than other query tools (e.g. DIG). Sample output from this query might look like this:
Using domain server: Name: 9.5.176.200 Address: 9.5.176.200#53 Aliases: aol.com has address 64.12.50.151 aol.com has address 205.188.142.182 aol.com mail is handled by 15 mailin-01.mx.aol.com. aol.com mail is handled by 15 mailin-02.mx.aol.com. aol.com mail is handled by 15 mailin-03.mx.aol.com. aol.com mail is handled by 15 mailin-04.mx.aol.com.
Example 2: Lookup with a Zone Transfer
HOST HOSTNAME(i5os.ibm.com) AXFR(*YES)
This command attempts to do a zone transfer. Sample output from this query might look like this:
Using domain server: Name: 10.0.1.100 Address: 10.0.1.100#53 Aliases: i5os.ibm.com name server MYDNS1.IBM.COM. i5os.ibm.com name server MYDNS2.IBM.COM. i5os.ibm.com has address 10.0.1.100 i5os.ibm.com has address 10.0.2.200 box1.i5os.ibm.com has address 10.0.2.201 box2.i5os.ibm.com has address 10.0.2.202
This command attempts to do the same zone transfer, but fails because the user is not authorized to do transfers. Sample output from this query might look like this:
Using domain server: Name: 10.0.1.100 Address: 10.0.1.100#53 Aliases: Host i5os.ibm.com not found: 9(NOTAUTH) ; Transfer failed.
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Error messages
*ESCAPE Messages
- DNS0013
- Error processing command parameters.
- DNS0065
- Option 33 of i5/OS is required, but is not installed.
- TCP7124
- Program &1 in library &2 type *PGM ended abnormally.
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