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This chapter explains how to configure some of the more advanced DNS zone and server parameters by using the Cisco Prime IP Express web UI and CLI. Before you proceed with the concepts in this chapter, read Managing Zones which explains how to set up the basic properties of a primary and secondary DNS server and its zones.
Resource records (RRs) comprise the data within a DNS zone. Although there is no fixed limit to the number of RRs a zone may own, in general, a zone may own one or more RRs of a given type (the zone always has a Start of Authority, or SOA, record). There are some exceptions depending on the types involved. All RRs have the entries described in the following table.
RR Entry |
Description |
---|---|
Name |
Owner of the record, such as a zone or hostname. |
Class (not required for all formats) |
Cisco Prime IP Express supports only the IN (Internet) class. |
TTL (time to live) |
Amount of time to store the record in a cache, in seconds. If you do not include a TTL, Cisco Prime IP Express uses the zone default TTL, defined as a zone attribute. |
Type |
Type of the record, such as A (AAAA for IPv6), NS, SOA, and MX. There are many types that various RFCs define, although fewer than ten are in common use. |
Record data |
Data types whose format and meaning varies with record type. |
Adding Resource Record to Zone
Protecting Resource Record Sets
Removing Resource Records from Zone
Searching Server-Wide for Records and Addresses
Advertising Services to Network Using Service Location (SRV) Records
Before adding or modifying RRs, keep in mind the two distinct dns edit modes that you can set and work in: staged and synchronous (see the "Staged and Synchronous Modes" section in Cisco Prime IP Express 9.0 DHCP User Guide).
Administrator roles required for RR management are the dns-admin role at the local cluster and the central-dns-admin role at the regional cluster. The host-admin role at the local cluster and the central-host-admin role at the regional cluster can view host records only.
Step 1 | Choose Forward Zones from Design > Auth DNS to open the List/Add Forward Zones page. | ||
Step 2 | In the
Forward Zone pane, click the zone name to open the Edit Zone page. Note that
resource record edits is managed jointly by CCM and DNS and a system lock is
used to prevent DNS and CCM from accessing the resource record database at the
same time.
| ||
Step 3 | Click the Resource Records tab. | ||
Step 4 | Add the RR name, TTL (if not using the default TTL), type, and data as appropriate. | ||
Step 5 | By default, RRs are protected, which means that DNS Updates cannot overwrite them (see Protecting Resource Record Sets). To unprotect the RRs, click the Locked icon to the left of the record name to change it to the Unlocked icon. Likewise, to protect the record, click the Unlocked icon to change it to the Locked icon. | ||
Step 6 | Click Add Resource Record. |
Use zone name addRR to add a protected RR of a certain type. You can specify the name as a relative name, if the owner is in the same domain, an absolute name (by supplying the FQDN), or the same name as the zone name (by using the at [@] symbol).
For example:
nrcmd> zone example.com addRR -sync host101 A 192.168.50.101
Use zone name addDNSRR type data to add an unprotected RR.
You can edit RRs as an individual record or as an RR set:
For a description of the fields to enter data, see Adding Resource Record to Zone.
You can remove RRs from a zone.
On the local or regional the Resource Records tab for the Zone page:
The CLI includes two removal commands, depending on the type of RR to remove:
You can manage the RRs for a host by configuring the host record rather than the individual RRs. When you define a host, the DNS server automatically creates an Address (A) RR for IPv4, or an AAAA RR for IPv6, for it. If the reverse zone for the host exists, the server can also create the associated Pointer (PTR) RR for it.
See Managing Hosts for details.
When an RR is protected, DNS Updates cannot modify the record. Most administratively created RRs are protected. However, RRs created by DNS Updates must be unprotected to allow the server to modify them. You can set this protection status for each RR set on the List/Add DNS Server RRs for Zone page.
Note that only the primary DNS server can recognize this protection status; secondary servers do not recognize the protection status of their RRs.
Caution | Zone scavenging can remove RRs that are unprotected. See the "Scavenging Dynamic Records" section in Cisco Prime IP Express 9.0 DHCP User Guide for details. |
To protect an existing RR, do the following:
You can also unprotect an RR. To unprotect an RR while adding, click the Locked icon next to the Resource Record name field. The icon changes to the Unlocked icon.
To unprotect an existing RR, do the following:
To protect the RR sets, use zone name protect-name rrset-name ; to unprotect the zone, use the unprotect-name rrset-name action instead. For example:
nrcmd> zone example.com protect-name boston 100 Ok protected boston nrcmd> zone example.com unprotect-name boston 100 Ok unprotected boston
With Cisco Prime IP Express, you can search for RRs and IP addresses server-wide. The search is a filter mechanism whereby you can specify a combination of RR and address attributes to target one or more RRs or addresses configured for the network. The search function is available at the local cluster only.
You can search RRs by:
To search resource records by IP address, do the following:
Step 1 | From the Operate menu, choose DNS > RR By IP Address from the Reports submenu to open the IP Address Search page. | ||
Step 2 | To search by
IP address, enter an IP address, then click
Search.
|
To search resource records, do the following:
Step 1 | From the Operate menu, choose DNS > Resource Records from Reports submenu to open the DNS Resource Record Search page. | ||
Step 2 | Choose a filter attribute from the drop-down list. | ||
Step 3 | Choose a filter type from the drop-down list depending on the filter attribute you chose: | ||
Step 4 | Enter or select a Value, based on the Type selected. To clear the filter, click Clear Filter. | ||
Step 5 | Click Add Element to add the search element to the filter elements list. The Filter Elements heading changes to identify the filter attribute and value used for the filter. If you add more than one element, the heading identifies the ANDed values of the elements. For example, if you add an element for a name prefix search for user, then add another element for an RR type search for A records, the filter element heading will identify the search as **RR Name Prefix = user AND RR Type = A. | ||
Step 6 | You can add as many elements as you like (remembering that the search results are an intersection of the filter elements). View the filter elements list by clicking the plus sign (+). | ||
Step 7 | Click Search. | ||
Step 8 | Check the
table of resulting RRs from the search, which shows for each RR its zone,
hostname, TTL, type, and associated data. If necessary, change the page size to
see more entries at one time (you might still need to page forward and back).
The RRs are sorted in DNSSEC order.
|
Use dns findRR to find RRs across the zones. The command syntax is of two kinds:
nrcmd> dns findRR -name{fqdn | domainaddr} nrcmd> dns findRR [-namePrefix nameprefix] [-rrTypes RRtypelist] [-protected| -unprotected] [-zoneType {forward| reverse| primary|secondary| ALL}]
You can search by domain or its address, or enter the beginning characters of the RR name (the name prefix). If you search by RR name prefix, you can narrow the search by a list of RR types, protection status, or zone type. The output clearly indicates the zone for each found entry. For example:
nrcmd> dns findRR -namePrefix user -rrTypes A userhost101.example.com IN A 192.168.50.101 userhost102.example.com IN A 192.169.50.102 userhost103.boston.example.com IN A 192.168.50.103
You might want to filter records to display only one type of record, such as an A (or IPv6 AAAA) or PTR record. (See also Searching Server-Wide for Records and Addresses.)
You can filter RRs right from the Edit Zone page. Look for the Name and Type fields just below the Add Resource Record button.
By default, RRs are sorted alphabetically by name, starting with the top-of-zone records (marked with the @ symbol), and secondarily sorted by type, then data. You can also sort them by:
When the selection is complete, click Filter List. This returns just the filtered entries in the table below the fields. To return to the full, unfiltered list, click Clear Filter.
Use zone zonename findRR to search on RR name prefixes, RR types, or protection status:
nrcmd> zone zonename findRR [-namePrefix nameprefix] [-rrTypes RRtypelist] [-protected| -unprotected]
The service location (SRV) RR is used to advertise services to the network. This RR is defined in the RFC 2782, “A DNS RR for specifying the location of services (DNS SRV).” The SRV can have an associated A or AAAA record. Windows domain controller is one service that uses the SRV records.
The RFC defines the format of the SRV record (DNS type code 33) as:
_service._protocol.name ttl class SRV priority weight port target
There should always be an A record associated with the SRV record target so that the client can resolve the service back to a host. In the Microsoft Windows implementation of SRV records, the records might look like this:
myserver.example.com A 201.165.201.1 _ldap._tcp.example.com SRV 0 0 389 myserver.example.com _kdc._tcp.example.com SRV 0 0 88 myserver.example.com _ldap._tcp.dc._msdcs.example.com SRV 0 0 88 myserver.example.com
An underscore (_) always precedes the service and protocol names. In the example, _kdc is the Key Distribution Center. The priority and weight help a client choose between target servers providing the same service (the weight differentiating those with equal priorities). If the priority and weight are all set to zero, the client orders the servers randomly.
Note | For a description of how Windows clients interoperate with DNS and DHCP servers, including scavenging dynamic RRs, see the "Configuring DNS Update for Windows Clients" section in Cisco Prime IP Express 9.0 DHCP User Guide. |
Cisco Prime IP Express supports Naming Authority Pointer (NAPTR) RRs. These records help with name resolution in a particular namespace and are processed to get to a resolution service. Because NAPTR records are a proposed standard, RFC 3403, Cisco Prime IP Express only validates their numeric record fields. However, the proposed standard requires a value for each field, even if it is null (“”), and there are no preset values.
When using a NAPTR record to locate a Session Initiation Protocol (SIP) proxy, see the proposed standard, RFC 2916 or RFC 3263. In RFC 2916, the ENUM working group of the Internet Engineering Task Force specifies NAPTR records to map E.164 addresses to Universal Resource Identifiers (URIs). Using the NAPTR record resolves a name in the E.164 international public telecommunication namespace to a URI, instead of providing the name of a service to use as a resolver. The U flag was added to the NAPTR record for this purpose.
For example, to specify a SIP proxy for the phone number +4689761234, add a NAPTR record at the name 4.3.2.1.6.7.9.8.6.4.e164.arpa. with this content:
100 10 "u" "sip+E2U" "/^.*$/sip:info@example.com/" .
This sets these fields of the NAPTR record:
order = 100 preference = 10 flags = "u" service = "sip+E2U" regexp = "/^.*$/sip:info@example.com/" replacement = .
After you configure these fields, the DNS client dealing with phone number +4689761234 can now find an SIP service URI by replacing the number with sip:info@tele2.se. The E.164 zone mostly uses the NAPTR record for wholesale replacement of the input telephone number. Section 3.2.3 of RFC 2916 includes an example of one transformation to a Lightweight Directory Access Protocol (LDAP) query that preserves some of the digits. The E.164 zone does not map to service location (SRV) records because it wants to obtain a SIP URL that is more humanly readable to the left of the at (@) symbol.
Step 1 | On the Edit Zone page, click the Resource Records tab. |
Step 2 | Enter the owner of the record in the Name field. |
Step 3 | Enter the TTL (if necessary). |
Step 4 | Click NAPTR in the Type drop-down list. |
Step 5 | Enter the
data as a string embedded in quotes and separated by spaces:
|
Step 6 | Click Add Resource Record. |
Use zone name addRR to add a protected resource record to a zone.