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Free DNS Monitoring

DNS Definition

DNS stands for Domain Name System. It translates domain names into IP addresses. The internet is based on IP addresses. However, IP addresses are a long series of arbitrary numbers. They are difficult to remember and relate to. Since domain names are alphabetic, they are much easier to remember. Whenever someone types a domain name in a browser, a DNS server translates the name into the corresponding IP address.

DNS Applications

DNS service is required by following common applications-

  • World wide web (www)
  • Email
  • Instant messaging
  • Multi-player games
  • Peer to peer applications
  • Web-services, etc

DNS Importance

If a DNS server is down or too slow, a website or web-service will appear as not available. This may happen even if the website or web-service itself may be up and running. Hence, it's important to monitor your DNS server for the following reasons -

  • If the DNS server is down, visitors will not be able to visit your website.
  • If the DNS server is slow, your website will appear to be slow even if your website is fast.
  • A hacker may point your domain name to their server.

DNS Monitoring

DNS monitoring is essential to ensure that an DNS server is available to users 24x7 and downtime is minimized. The free service provided by MonTools can monitor your DNS server and send you free alerts in case of following common issues -

  • DNS server down
  • DNS server slow
  • Domain IP Mismatch

DNS Monitor Settings

The DNS monitor supports following settings -

  • Monitoring Interval - This field lets you select the DNS check interval or DNS monitoring interval. For example, if you select "1 Hour", then the DNS server is checked once every 1 hour. Monitoring intervals are supported from 1 minute to 1 day.
  • Domain Name - Domain name or website name to be monitored. The monitor will check the DNS server if a record for the specified domain/website exists.
  • Domain IP - IP address of the domain or the website. The monitor will verify that the specified IP address matches the DNS server response. You can click on the "Auto Detect" button, and our system will automatically detect the IP address for the given domain (above) and enter it in this field.
  • DNS Port - Applications talk to DNS servers on port 53. However, for custom applications, it can be some port other than 53.
  • DNS Host - Host name of the DNS server to be monitored. The monitor will verify that the DNS server is available. You can click on the "Auto Detect" button, and our system will automatically detect the DNS servers for the given domain (above) and let you select one.

DNS Response

The monitor can be set to trigger on following conditions-

  1. DNS Down - This condition is triggered if one or more of the following conditions are true-
    • DNS server is down
    • Response from DNS server takes longer than specified timeout
    • DNS record for the specified domain/website doesn't exist
    • IP address returned by the DNS server doesn't match the expected Domain IP
  2. Connection Error - This condition is triggered only if DNS server is down.
  3. Response Time - This condition can be configured to trigger whenever the response time exceeds a certain time limit.

Additionally, you can set the monitor to trigger on mismatch/match on following DNS records-

  1. A - address record
    Returns a 32-bit IPv4 address, most commonly used to map hostnames to an IP address of the host, but also used for DNSBLs, storing subnet masks in RFC 1101, etc.
  2. AAAA - IPv6 address record
    Returns a 128-bit IPv6 address, most commonly used to map hostnames to an IP address of the host.
  3. AFSDB - AFS database record
    Location of database servers of an AFS cell. This record is commonly used by AFS clients to contact AFS cells outside their local domain. A subtype of this record is used by the obsolete DCE/DFS file system.
  4. ATMA - ATMA resource record
    Used to map DNS domain names to Asynchronous Transfer Mode addresses
  5. AXFR - AXFR record
    DNS zone transfer
  6. CNAME - Canonical name record
    Alias of one name to another: the DNS lookup will continue by retrying the lookup with the new name.
  7. EID - EID record
    Endpoint Identifier
  8. GID - GID record
    IANA-Reserved
  9. GPOS - GPOS record
    Geographical Position
  10. HINFO - HINFO record
    Host information
  11. ISDN - ISDN record
    ISDN address
  12. IXFR - IXFR record
    Incremental transfer
  13. KEY - key record
    Used only for SIG(0) (RFC 2931) and TKEY (RFC 2930). RFC 3445 eliminated their use for application keys and limited their use to DNSSEC. RFC 3755 designates DNSKEY as the replacement within DNSSEC.
  14. LOC - Location record
    Specifies a geographical location associated with a domain name
  15. MAILA - MAILA record
    Mail agent RRs (Obsolete - see MX)
  16. MAILB - MAILB record
    Mailbox-related RRs (MB, MG or MR)
  17. MB - MB record
    Mailbox domain name (EXPERIMENTAL)
  18. MD - MD record
    Mail destination (Obsolete - use MX)
  19. MF - MF record
    Mail forwarder (Obsolete - use MX)
  20. MG - MG record
    Mail group member (EXPERIMENTAL)
  21. MINFO - MINFO record
    Mailbox or mail list information
  22. MR - MR record
    Mail rename domain name (EXPERIMENTAL)
  23. MX - mail exchange record
    Maps a domain name to a list of message transfer agents for that domain
  24. NAPTR - Naming Authority Pointer
    Allows regular expression based rewriting of domain names which can then be used as URIs, further domain names to lookups, etc.
  25. NIMLOC - NIMLOC record
    Nimrod Locator
  26. NS - name server record
    Delegates a DNS zone to use the given authoritative name servers
  27. NSAP_PTR - NSAP_PTR record
    For domain name pointer, NSAP style
  28. NSAP - NSAP record
    For NSAP address, NSAP style A record
  29. NULL - NULL record
    Null RR
  30. NXT - NXT record
    Next Domain - OBSOLETE
  31. PTR - pointer record
    Pointer to a canonical name. Unlike a CNAME, DNS processing does NOT proceed, just the name is returned. The most common use is for implementing reverse DNS lookups, but other uses include such things as DNS-SD.
  32. PX - PX record
    X.400 mail mapping information
  33. RP - Responsible person
    Information about the responsible person(s) for the domain. Usually a email address with the @ replaced by a .
  34. RT - RT record
    For Route Through
  35. SIG - Signature
    Signature record used in SIG(0) (RFC 2931) and TKEY (RFC 2930). RFC 3755 designated RRSIG as the replacement for SIG for use within DNSSEC.
  36. SOA - start of authority record
    Specifies authoritative information about a DNS zone, including the primary name server, the email of the domain administrator, the domain serial number, and several timers relating to refreshing the zone.
  37. SPF - Sender Policy Framework
    Specified as part of the SPF protocol in preference to the earlier provisional practice of storing SPF data in TXT records. Uses the same format as the earlier TXT record.
  38. SRV - Service locator
    Generalized service location record, used for newer protocols instead of creating protocol-specific records such as MX.
  39. TSIG - Transaction Signature
    Can be used to authenticate dynamic updates as coming from an approved client, or to authenticate responses as coming from an approved recursive name server similar to DNSSEC.
  40. TXT - Text record
    Originally for arbitrary human-readable text in a DNS record. Since the early 1990s, however, this record more often carries machine-readable data, such as specified by RFC 1464, opportunistic encryption, Sender Policy Framework (although this provisional use of TXT records is deprecated in favor of SPF records), DomainKeys, DNS-SD, etc.
  41. UID - UID record
    IANA-Reserved
  42. UINFO - UINFO record
    IANA-Reserved
  43. UNSPEC - UNSPEC record
    IANA-Reserved
  44. WKS - WKS record
    A well known service description
  45. X25 - X25 record
    For X.25 PSDN address

DNS Alerts

Whenever the monitor detects the DNS server down or any other issues, or any other configured conditions are triggered, it can send you and/or your colleagues a free alert with one or more of the following methods-

  1. Email alert
  2. SMS alert
  3. Twitter alert (private message)
  4. Callback URL

DNS Logs, Stats & Graphs

Logs, stats and graphs are available for uptime, monitor status and DNS response time.


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