Description and usage of SRV records

SRV record: It is generally an application set for Microsoft's Active Directory. DNS can be independent from the Active Directory, but the Active Directory must have DNS help to work. In order for the Active Directory to work normally, the DNS server must support the service locating (SRV) resource record, and the resource record maps the service name to the name of the server that provides the service. Active Directory customers and domain controllers use SRV resource records to determine the IP addresses of domain controllers. S> xabt: m
SRV record functions include (based on their groups on the DNS console)
'_ Msdcs. In this group, SRV records are collected based on their statuses. Various statuses include DC, domain call, GC, and PDC. DC and GC are divided by site, so that the ad client can quickly find the local service. "Domain call" is used to support replication. Each DC obtains a guid, which is used when replication is called. The PDC entry contains the SRV record of the DC set as the PDC simulator.
'_ Sites. The site represents a high-speed connection area. After a DC index is created based on the DC's site subordination, the client can check _ sites to find the local service, instead of sending LDAP query requests over the WAN. The standard LDAP query port is 389, and the Global Catalog query uses 3268.
'_ TCP. This group collects all the DC in the DNS region. If the client cannot find their specific site, or any DC with a local SRV record does not respond, you need to find the DC in other parts of the network, you should put these clients in this group.
'_ UDP. Keberos V5 allows the client to use the "No connection" service to obtain the ticket and change the password. This is done through the UDP port corresponding to the TCP port of the same service. Specifically, the ticket exchange uses port 88 of UDP, while the Password Change uses port 464.

 

Next, let's take a look at whether the SRV records in the Active Directory, such as DC and GC, are complete!

Y: \> NSLookup

Default Server: Tom. ***. com

Address: 192.168.1.2

 

> Set type = srv

The following command is used to view the SRV record of the DC. The blue font indicates the command input result!

> _ LDAP. _ TCP. DC. _ msdcs. ***. com

Server: Tom. ***. com

Address: 192.168.1.2

 

_ LDAP. _ TCP. DC. _ msdcs. ***. com SRV service location:

Priority = 0

Weight = 100

Port = 389

SVR hostname = Mary. ***. com

_ LDAP. _ TCP. DC. _ msdcs. ***. com SRV service location:

Priority = 0

Weight = 100

Port = 389

SVR hostname = Tom. ***. com

Mary. ***. COM Internet address = 192.168.1.3

Tom. ***. COM Internet address = 192.168.1.2

The following command is used to view the SRV records of GC. The blue font indicates the command input result!

> _ LDAP. _ TCP. gc. _ msdcs. ***. com

Server: Tom. ***. com

Address: 192.168.1.2

 

_ LDAP. _ TCP. gc. _ msdcs. ***. com SRV service location:

Priority = 0

Weight = 100

Port = 3268

SVR hostname = Tom. ***. com

_ LDAP. _ TCP. gc. _ msdcs. ***. com SRV service location:

Priority = 0

Weight = 100

Port = 3268

SVR hostname = Mary. ***. com

Tom. ***. COM Internet address = 192.168.1.2

Mary. ***. COM Internet address = 192.168.1.3

The following command is used to view the SRV record of the PDC. The blue font indicates the command input result!

> _ LDAP. _ TCP. PDC. _ msdcs. ***. com

Server: Tom. ***. com

Address: 192.168.1.2

 

_ LDAP. _ TCP. PDC. _ msdcs. ***. com SRV service location:

Priority = 0

Weight = 100

Port = 389

SVR hostname = Tom. ***. com

Tom. ***. COM Internet address = 192.168.1.2

 

The Automatic Discovery Function of the OCS client also uses the SRV record to find the front-end server information for logon.

For the SRV record configuration of OCS, the deployment documentation is described as follows:

To enable automatic IC configuration for your clients, you must create an internal dns srv record that maps one of the following records to the FQDN of the Enterprise Edition pool (or Standard Edition server) that distribute sign-in requests from office COMMUNICATOR:

_ Sipinternaltls. _ TCP. <Domain>-For internal TLS connections

_ Sipinternal. _ TCP. <Domain>-For internal TCP connections (timed med only if TCP is allowed)

Based on the previous knowledge, we can use the following command to find the FQDN, IP, and port information of the OCS front-end server.

 

> _ Sipinternaltls. _ TCP. <domain>
Server: ***. <domain>
Address: 10.10.10.1

_ Sipinternaltls. _ TCP. <domain> SRV service location:
Priority = 0
Weight = 100
Port =5061
SVR hostname =Ocspool01. <domain>
Ocspool01. <domain> Internet address =10.10.10.4