This key must be handled with extreme caution, since if it is exposed or can be read either on the DNS server or the DHCP server or any other location where it is stored for "safe-keeping" it is compromised and must be discarded and a new key generated. Clearly the last thing any attacker will do is to boast that they have discovered the key, rather they will elect to happily and silently cause as much damage as possible.
The following configurations attempt to minimise the possibility of key compromise. The -a hmac-md5 argument defines the type of TSIG shared secret we are using. DHCP only supports hmac-md5 dnssec-keygen supports many other types. The -b argument indicates the number of bits to be used in the HMAC range 1 - , -n host is mandatory when generating TSIG keys the -C ddns-a-rrs argument should be used with modern versions of BIND it omits timing and state meta data.
If your version of dnssec-keygen chokes on -C it can be omitted and your version of BIND should be immediately updated. Feel free to let your imagination run wild with key names. The output message Kddns-a-rrs. Inspection of the file Kddns-a-rrs. This is an artifact of the keygen process and is not used in our configuration. Its presence is a security risk - delete this file. Edit this file to look like the following a key clause and save it to the same file name:. Essentially, the material which appears after Key: is the base secret key and must be unchanged on the secret line in the edited file structure though terminated with a ; , some folks enclose this material in quotes "" to make it easier to work with, though this is not a requirement.
Note: Much confusion reigns over when to use a quoted string and when it does not matter. In general, the rule says that if the item contains a space character it must be enclosed in quotes otherwise it's optional. Since the key material is encoded in base64 it can never contain a space so quotes are not essential. Note for the Perennially Curious: In the example above the key material consists of 24 characters. This is the base64 representation of bits the -b dnssec-keygen argument.
Base64 uses a 6-bit character set ASCII is a 7-bit code that explicitly excludes the space character. RFC contains all the gruesome details. The resulting key clause file contains the shared secret and thus presents a security risk.
The file is saved to the same name to ensure that we do not have multiple copies lying around - always a poor policy. You can subsequently rename the file if required it does have a horrible name format , the objective being to keep a single copy of this file. Assuming you generated this file on the DNS server, secure the file with read only permission for the user BIND runs as, normally named Linux or bind BSD better yet, secure it for read only access by root if you have root access.
If you copy the file from a third party machine make sure to delete it or a the very least secure it with minimal read-only permissions.
This file will be included as shown in both the dhcpd. The use of include is a further security precaution, in the event your.
Depending on your local policy another key called, say, ddns-ptr-rrs can be generated and the same process followed. Alternatively, you may choose to use a single key for both in which case a more appropriate key-name may be something like anyone-anytime.
Just kidding. As a general matter of policy a single key should be used for a single function from a single source. Not always possible or practical but always the best policy where it is. The key ddns-a-rrs and key ddns-ptr-rrs statements in the respective zone clauses bind the use of the key-name to any transaction. This means it is possible to have key-per-zone configuration granularity. It is assumed both the forward and reverse zone are supported by the same name server for simplicity.
When both DHCP and BIND are loaded they initially run as root to allocate priority port numbers among other functions before issuing a suid call to change to their normal -u account.
The include statements are processed during the root user period which means that key files set read-only under root can be read. Both are shown in the same zone clause a load-time error for illustrative purposes only. Many variation are both relevant and applicable depending on the requirements. The policy shown in the examples is one of many possibilities. When the mobile node is at home, it connects to the home link and uses its home address.
When the mobile node is away from home, a home agent, which is usually a router, relays messages between the mobile node and nodes with which it is communicating. Skip to main content. This browser is no longer supported. Download Microsoft Edge More info. Contents Exit focus mode. Is this page helpful? Please rate your experience Yes No. Any additional feedback? Additionally, the primary full computer name is the primary DNS suffix of the computer that is appended to the computer name.
This includes connections that are not configured to use DHCP. By default, Windows registers A and PTR resource records every 24 hours regardless of the computer's role. Dynamic updates are typically requested when either a DNS name or an IP address changes on the computer. For example, a client named "oldhost" is first configured in system properties to have the following names: Computer name: oldhost DNS domain name of computer: example. In this example, no connection-specific DNS domain names are configured for the computer.
If you rename the computer from "oldhost" to "newhost", the following name changes occur: Computer name: newhost DNS domain name of computer: example. After the name change is applied in System Properties , Windows prompts you to restart the computer. The client computer uses the currently configured FQDN of the computer, such as " newhost.
For standard primary zones, the primary server, or owner, that is returned in the SOA query response is fixed and static. The primary server name always matches the exact DNS name as that name is displayed in the SOA resource record that is stored with the zone.
However, if the zone that is being updated is directory-integrated, any DNS server that is loading the zone can respond and dynamically insert its own name as the primary server of the zone in the SOA query response.
The client processes the SOA query response for its name to determine the IP address of the DNS server that is authorized as the primary server for accepting its name.
If it is required, the client performs the following steps to contact and dynamically update its primary server:. The client sends a dynamic update request to the primary server that is determined in the SOA query response.
If this update fails, the client next sends an NS-type query for the zone name that is specified in the SOA record. When the client receives a response to this query, the client sends an SOA query to the first DNS server that is listed in the response.
After the SOA query is resolved, the client sends a dynamic update to the server that is specified in the returned SOA record. If this update fails, the client repeats the SOA query process by sending to the next DNS server that is listed in the response. After the primary server that can perform the update is contacted, the client sends the update request, and the server processes it. The contents of the update request include instructions to add A, and possibly PTR, resource records for " newhost.
The server also checks to make sure that updates are permitted for the client request. For standard primary zones, dynamic updates are not secured. Any client attempt to update succeeds. For Active Directory-integrated zones, updates are secured and performed using directory-based security settings. Dynamic updates are sent or refreshed periodically. By default, computers send an update every twenty-four hours. If the update causes no changes to zone data, the zone remains at its current version, and no changes are written.
Updates that cause actual zone changes or increased zone transfers occur only if names or addresses actually change. Names are not removed from DNS zones if they become inactive or if they are not updated within the update interval of twenty-four hours. DNS does not use a mechanism to release or to tombstone names, although DNS clients do try to delete or to update old name records when a new name or address change is applied. This value determines how long other DNS servers and clients cache a computer's records when they are included in a query response.
Scope clients can use the DNS dynamic update protocol to update their host name-to-address mapping information whenever changes occur to their DHCP-assigned address. This mapping information is stored in zones on the DNS server. This enables the client to notify the DHCP server as to the service level it requires. In this case, the option is processed and interpreted by Windows Server-based DHCP servers to determine how the server initiates updates on behalf of the client.
This is the default configuration for Windows. To configure the DHCP server to register client information according to the client's request, follow these steps:. By default, updates are always performed for newly installed Windows Server-based DHCP servers and any new scopes that you create for them. The following examples show how this process varies in different cases. For these DHCP clients, updates are typically handled in the following manner:. After you integrate a zone, you can use the access control list ACL editing features that are available in the DNS snap-in to add or to remove users or groups from the ACL for a specific zone or for a resource record.
For more information, search for the "To modify security for a resource record" topic or the "To modify security for a directory integrated zone" topic in Windows Server Help.
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