Manual:IP/DNS
Applies to RouterOS: v4.6
DNS cache is used to minimize DNS requests to an external DNS server as well as to minimize DNS resolution time. This is a simple DNS cache with local items.
Specifications
- Packages required: system
- License required: Level1
- Submenu level: /ip dns
- Standards and Technologies: DNS
- Hardware usage: Not significant
Description
A MikroTik router with DNS feature enabled can be set as a DNS server for any DNS-compliant client. Moreover, MikroTik router can be specified as a primary DNS server under its dhcp-server settings. When the remote requests are enabled, the MikroTik router responds to TCP and UDP DNS requests on port 53.
DNS Cache Setup
Sub-menu: /ip dns
DNS facility is used to provide domain name resolution for router itself as well as for the clients connected to it.
Properties
| Property | Description |
|---|---|
| allow-remote-requests (yes | no; Default: no) | Specifies whether to allow network requests |
| cache-max-ttl (time; Default: 1w) | Maximum time-to-live for cache records. In other words, cache records will expire unconditionally after cache-max-ttl time. Shorter TTL received from DNS servers are respected. |
| cache-size (integer[64..4294967295]; Default: 2048) | Specifies the size of DNS cache in KiB |
| max-concurrent-queries (integer; Default: 100) | Specifies how much concurrent queries are allowed |
| max-concurrent-tcp-sessions (integer; Default: 20) | Specifies how much concurrent TCP sessions are allowed |
| max-udp-packet-size (integer [50..65507]; Default: 4096) | Maximum size of allowed UDP packet. |
| query-server-timeout (time; Default: 2s) | Specifies how long to wait for query response from one server |
| query-total-timeout (time; Default: 10s) | Specifies how long to wait for query response in total. Note that this setting must be configured taking into account query-server-timeout and number of used DNS server. |
| servers (list of IPv4/IPv6 addresses; Default: ) | List of DNS server IPv4/IPv6 addresses |
Read-only Properties
| Property | Description |
|---|---|
| cache-used (integer) | Shows the currently used cache size in KiB |
| dynamic-server (IPv4/IPv6 list) | List of dynamically added DNS server from different services, for exammple, DHCP. |
Note: If allow-remote-requests is used make sure that you limit access to your server over TCP and UDP protocol.
Example
To set 159.148.60.2 as the primary DNS server and allow the router to be used as a DNS server, do the following:
[admin@MikroTik] ip dns> set servers=159.148.60.2 \
\... allow-remote-requests=yes
[admin@MikroTik] ip dns> print
servers: 159.148.60.2
allow-remote-requests: yes
cache-size: 2048KiB
cache-max-ttl: 1w
cache-used: 7KiB
[admin@MikroTik] ip dns>
Cache Monitoring
- Submenu level: /ip dns cache
Description
This menu provides a list with all address (DNS type "A") records stored on the server
Property Description
| Property | Desciption |
|---|---|
| address (read-only: IP address) | IP address of the host |
| name (read-only: name) | DNS name of the host |
| ttl (read-only: time) | remaining time-to-live for the record |
All DNS Entries
- Submenu level: /ip dns cache all
Description
This menu provides a complete list with all DNS records stored on the server
Property Description
| Property | Desciption |
|---|---|
| data (read-only: text) | DNS data field. IP address for type "A" records. Other record types may have different contents of the data field (like hostname or arbitrary text) |
| name (read-only: name) | DNS name of the host |
| ttl (read-only: time) | remaining time-to-live for the record |
| type (read-only: text) | DNS record type |
Static DNS Entries
- Submenu level: /ip dns static
Description
The MikroTik RouterOS has an embedded DNS server feature in DNS cache. It allows you to link the particular domain names with the respective IP addresses and advertize these links to the DNS clients using the router as their DNS server. This feature can also be used to provide fake DNS information to your network clients. For example, resolving any DNS request for a certain set of domains (or for the whole Internet) to your own page.
The server is capable of resolving DNS requests based on POSIX basic regular expressions, so that multiple requets can be matched with the same entry. In case an entry does not conform with DNS naming standards, it is considered a regular expression and marked with ‘R’ flag. The list is ordered and is checked from top to bottom. Regular expressions are checked first, then the plain records.
Property Description
| Property | Desciption |
|---|---|
| address (IP address) | IP address to resolve domain name with |
| name (text) | DNS name to be resolved to a given IP address. |
| regex (text) | DNS regex |
| ttl (time) | time-to-live of the DNS record |
Notes
Reverse DNS lookup (Address to Name) of the regular expression entries is not possible. You can, however, add an additional plain record with the same IP address and specify some name for it.
Remember that the meaning of a dot (.) in regular expressions is any character, so the expression should be escaped properly. For example, if you need to match anything within example.com domain but not all the domains that just end with example.com, like www.another-example.com, use name=".*\\.example\\.com"
Regular expression matching is significantly slower than of the plain entries, so it is advised to minimize the number of regular expression rules and optimize the expressions themselves. Example
To add a static DNS entry for www.example.com to be resolved to 10.0.0.1 IP address:
[admin@MikroTik] ip dns static> add name=www.example.com address=10.0.0.1 [admin@MikroTik] ip dns static> print Flags: D - dynamic, X - disabled, R - regexp # NAME ADDRESS TTL 0 www.example.com 10.0.0.1 1d [admin@MikroTik] ip dns static>
Or use regex to match DNS requests:
[admin@MikroTik] ip dns static> add regexp="[*example*]" address=10.0.0.2
For more information how to use regex, read wiki page below.
Flushing DNS cache
- Command name: /ip dns cache flush
Command Description
| Command | Desciption |
|---|---|
| flush | clears internal DNS cache |
Example
[admin@MikroTik] ip dns> cache flush
[admin@MikroTik] ip dns> print
servers: 159.148.60.2
allow-remote-requests: yes
cache-size: 2048 KiB
cache-max-ttl: 1w
cache-used: 10 KiB
[admin@MikroTik] ip dns>