Firewall filters are used to allow or block specific packets forwarded to your local network, originated from your router, or destined to the router.
There are two methods on how to set up filtering:
Both methods have pros and cons, for example, from a security point of view first method is much more secure, but requires administrator input whenever traffic for new service needs to be accepted. This strategy provides good control over the traffic and reduces the possibility of a breach because of service misconfiguration.
On the other hand, when securing a customer network it would be an administrative nightmare to accept all possible services that users may use. Therefore careful planning of the firewall is essential in advanced setups.
A firewall filter consists of three predefined chains that cannot be deleted:
When processing a chain, rules are taken from the chain in the order they are listed there from top to bottom. If a packet matches the criteria of the rule, then the specified action is performed on it, and no more rules are processed in that chain (the exception is the passthrough action). If a packet has not matched any rule within the built-in chain, then it is accepted. More detailed packet processing in RouterOS is described in the Packet Flow in RouterOS diagram.
Property | Description |
---|---|
action (action name; Default: accept) | Action to take if a packet is matched by the rule:
|
address-list-timeout (none-dynamic | none-static | time; Default: none-dynamic) | Time interval after which the address will be removed from the address list specified by address-list parameter. Used in conjunction with add-dst-to-address-list or add-src-to-address-list actions
|
chain (name; Default: ) | Specifies to which chain rule will be added. If the input does not match the name of an already defined chain, a new chain will be created |
comment (string; Default: ) | Descriptive comment for the rule |
chain (name; Default: ) | Specifies to which chain rule will be added. If the input does not match the name of an already defined chain, a new chain will be created |
comment (string; Default: ) | Descriptive comment for the rule |
connection-bytes (integer-integer; Default: ) | Matches packets only if a given amount of bytes has been transferred through the particular connection. 0 - means infinity, for example connection-bytes=2000000-0 means that the rule matches if more than 2MB has been transferred through the relevant connection |
connection-limit (integer,netmask; Default: ) | Matches connections per address or address block after a given value is reached. Should be used together with connection-state=new and/or with tcp-flags=syn because matcher is very resource-intensive |
connection-mark (no-mark | string; Default: ) | Matches packets marked via mangle facility with particular connection mark. If no-mark is set, the rule will match any unmarked connection |
connection-nat-state (srcnat | dstnat; Default: ) | Can match connections that are srcnatted, distracted, or both. Note that connection-state=related connections connection-nat-state is determined by the direction of the first packet. and if connection tracking needs to use dst-nat to deliver this connection to the same hosts as the main connection it will be in connection-nat-state=dstnat even if there are no dst-nat rules at all |
connection-rate (Integer 0..4294967295; Default: ) | Connection Rate is a firewall matcher that allows capturing traffic based on the present speed of the connection |
connection-state (established | invalid | new | related | untracked; Default: ) | Interprets the connection tracking analytics data for a particular packet:
|
connection-type (ftp | h323 | irc | pptp | quake3 | sip | tftp; Default: ) | Matches packets from related connections based on information from their connection tracking helpers. A relevant connection helper must be enabled under the: /ip firewall service-port |
content (string; Default: ) | Match packets that contain specified text |
dscp (integer: 0..63; Default: ) | Matches DSCP IP header field. |
dst-address (IP/netmask | IP range; Default: ) | Matches packets which destination is equal to specified IP or falls into specified IP range. |
dst-address-list (name; Default: ) | Matches destination address of a packet against user-defined address-list. |
dst-address-type (unicast | local | broadcast | multicast | blackhole | prohibit | unreachable ; Default: ) | Matches destination address type:
|
dst-limit (integer[/time],integer,dst-address | dst-port | src-address[/time]; Default: ) | Matches packets until a given rate is exceeded. Rate is defined as packets per time interval. As opposed to the limit matcher, every flow has its own limit. Flow is defined by a mode parameter. Parameters are written in the following format: rate[/time],burst,mode[/expire] .
|
dst-port (integer[-integer]: 0..65535; Default: ) | List of destination port numbers or port number ranges |
fragment (yes|no; Default: ) | Matches fragmented packets. The first (starting) fragment does not count. If connection tracking is enabled there will be no fragments as the system automatically assembles every packet |
hotspot (auth | from-client | http | local-dst | to-client; Default: ) | Matches packets received from HotSpot clients against various HotSpot matchers.
|
icmp-options (integer:integer; Default: ) | Matches ICMP type: code fields |
in-bridge-port (name; Default: ) | Actual interface the packet has entered the router if the incoming interface is a bridge. Works only if use-ip-firewall is enabled in bridge settings. |
in-bridge-port-list (name; Default: ) | Set of interfaces defined in interface list. Works the same as in-bridge-port |
in-interface (name; Default: ) | Interface the packet has entered the router |
in-interface-list (name; Default: ) | Set of interfaces defined in interface list. Works the same as in-interface |
ingress-priority (integer: 0..63; Default: ) | Matches the priority of an ingress packet. Priority may be derived from VLAN, WMM, DSCP, or MPLS EXP bit. read more |
ipsec-policy (in | out, ipsec | none; Default: ) | Matches the policy used by IPsec. Value is written in the following format: direction, policy . The direction is Used to select whether to match the policy used for decapsulation or the policy that will be used for encapsulation.
For example, if a router receives an IPsec encapsulated Gre packet, then rule |
ipv4-options (any | loose-source-routing | no-record-route | no-router-alert | no-source-routing | no-timestamp | none | record-route | router-alert | strict-source-routing | timestamp; Default: ) | Matches IPv4 header options.
|
jump-target (name; Default: ) | Name of the target chain to jump to. Applicable only if action=jump |
layer7-protocol (name; Default: ) | Layer7 filter name defined in layer7 protocol menu. |
limit (integer,time,integer; Default: ) | Matches packets up to a limited rate (packet rate or bit rate). A rule using this matcher will match until this limit is reached. Parameters are written in the following format: rate[/time],burst:mode .
|
log (yes | no; Default: no) | Add a message to the system log containing the following data: in-interface, out-interface, src-mac, protocol, src-ip:port->dst-ip:port, and length of the packet. |
log-prefix (string; Default: ) | Adds specified text at the beginning of every log message. Applicable if action=log or log=yes configured. |
nth (integer,integer; Default: ) | Matches every nth packet: nth=2,1 rule will match every first packet of 2, hence, 50% of all the traffic that is matched by the rule |
out-bridge-port (name; Default: ) | Actual interface the packet is leaving the router if the outgoing interface is a bridge. Works only if use-ip-firewall is enabled in bridge settings. |
out-bridge-port-list (name; Default: ) | Set of interfaces defined in interface list. Works the same as out-bridge-port |
out-interface (; Default: ) | Interface the packet is leaving the router |
out-interface-list (name; Default: ) | Set of interfaces defined in interface list. Works the same as out-interface |
packet-mark (no-mark | string; Default: ) | Matches packets marked via mangle facility with particular packet mark. If no-mark is set, the rule will match any unmarked packet. |
packet-size (integer[-integer]:0..65535; Default: ) | Matches packets of specified size or size range in bytes. |
per-connection-classifier (ValuesToHash:Denominator/Remainder; Default: ) | PCC matcher allows dividing traffic into equal streams with the ability to keep packets with a specific set of options in one particular stream. Read more >> |
port (integer[-integer]: 0..65535; Default: ) | Matches if any (source or destination) port matches the specified list of ports or port ranges. Applicable only if protocol is TCP or UDP |
priority (integer: 0..63; Default:) | Matches the packet's priority after a new priority has been set. Priority may be derived from VLAN, WMM, DSCP, MPLS EXP bit, or from the priority that has been set using the set-priority action. Read more |
protocol (name or protocol ID; Default: tcp) | Matches particular IP protocol specified by protocol name or number |
psd (integer,time,integer,integer; Default: ) | Attempts to detect TCP and UDP scans. Parameters are in the following format WeightThreshold, DelayThreshold, LowPortWeight, HighPortWeight
|
random (integer: 1..99; Default: ) | Matches packets randomly with a given probability |
reject-with (icmp-admin-prohibited | icmp-net-prohibited | icmp-protocol-unreachable | icmp-host-prohibited | icmp-network-unreachable | tcp-reset | icmp-host-unreachable | icmp-port-unreachable; Default: icmp-network-unreachable) | Specifies ICMP error to be sent back if the packet is rejected. Applicable if action=reject |
routing-table (string; Default: ) | Matches packets which destination address is resolved in specific a routing table. |
routing-mark (string; Default: ) | Matches packets marked by mangle facility with particular routing mark |
src-address (Ip/Netmask, Ip range; Default: ) | Matches packets which source is equal to specified IP or falls into a specified IP range |
src-address-list (name; Default: ) | Matches source address of a packet against user-defined address list |
src-address-type (unicast | local | broadcast | multicast | blackhole | prohibit | unreachable ; Default: ) | mote{ta{tableMatches source address type:
|
src-port (integer[-integer]: 0..65535; Default: ) | List of source ports and ranges of source ports. Applicable only if a protocol is TCP or UDP |
src-mac-address (MAC address; Default: ) | Matches source MAC address of the packet |
tcp-flags (ack | cwr | ece | fin | psh | rst | syn | urg; Default: ) | Matches specified TCP flags
|
tcp-mss (integer[-integer]: 0..65535; Default: ) | Matches TCP MSS value of an IP packet |
time (time-time,sat | fri | thu | wed | tue | mon | sun; Default: ) | Allows to create a filter based on the packets' arrival time and date or, for locally generated packets, departure time and date |
tls-host (string; Default: ) | Allows matching HTTPS traffic based on TLS SNI hostname. Accepts GLOB syntax for wildcard matching. Note that the matcher will not be able to match hostname if the TLS handshake frame is fragmented into multiple TCP segments (packets). Watch our video about this value. |
ttl (integer: 0..255; Default: ) | Matches packets TTL value |
To show additional read-only properties:
/ip firewall filter print stats
Property | Description |
---|---|
bytes (integer) | The total amount of bytes matched by the rule |
packets (integer) | The total amount of packets matched by the rule |
[admin@MikroTik] > ip firewall filter print stats Flags: X - disabled, I - invalid, D - dynamic # CHAIN ACTION BYTES PACKETS 0 D ;;; special dummy rule to show fasttrack counters forward passthrough 50 507 925 242 50 048 246 1 ;;; defconf: drop invalid forward drop 432 270 9 719 2 ;;; defconf: drop invalid input drop 125 943 2 434 3 input accept 20 090 211 549 20 009 864 4 ;;; defconf: accept ICMP input accept 634 926 7 648 5 ;;; defconf: drop all not coming from LAN input drop 4 288 079 83 428 6 ;;; defconf: accept in ipsec policy forward accept 0 0 7 ;;; defconf: accept out ipsec policy forward accept 0 0 8 ;;; defconf: fasttrack forward fasttrack-connection 28 505 528 775 31 504 682 9 ;;; defconf: accept established,related, untracked forward accept 28 505 528 775 31 504 682 10 ;;; defconf: drop all from WAN not DSTNATed forward drop 0 0
/ipv6/firewall/filter
Property | Description |
---|---|
action (accept | add-dst-to-address-list | ...; Default: accept) | Action to take if a packet is matched by the rule:
|
address-list-timeout (none-dynamic | none-static | time; Default: none-dynamic) | Time interval after which the address will be removed from the address list specified by address-list parameter. Used in conjunction with add-dst-to-address-list or add-src-to-address-list actions
|
chain (name; Default: ) | Specifies to which chain rule will be added. If the input does not match the name of an already defined chain, a new chain will be created |
comment (string; Default: ) | Descriptive comment for the rule |
chain (name; Default: ) | Specifies to which chain rule will be added. If the input does not match the name of an already defined chain, a new chain will be created |
comment (string; Default: ) | Descriptive comment for the rule |
connection-bytes (integer-integer; Default: ) | Matches packets only if a given amount of bytes has been transferred through the particular connection. 0 - means infinity, for example connection-bytes=2000000-0 means that the rule matches if more than 2MB has been transferred through the relevant connection |
connection-limit (integer,netmask; Default: ) | Matches connections per address or address block after a given value is reached. Should be used together with connection-state=new and/or with tcp-flags=syn because matcher is very resource-intensive |
connection-mark (no-mark | string; Default: ) | Matches packets marked via mangle facility with particular connection mark. If no-mark is set, the rule will match any unmarked connection |
connection-rate (Integer 0..4294967295; Default: ) | Connection Rate is a firewall matcher that allows capturing traffic based on the present speed of the connection |
connection-state (established | invalid | new | related | untracked; Default: ) | Interprets the connection tracking analytics data for a particular packet:
|
connection-type (ftp | h323 | irc | pptp | quake3 | sip | tftp; Default: ) | Matches packets from related connections based on information from their connection tracking helpers. A relevant connection helper must be enabled under the: /ip firewall service-port |
content (string; Default: ) | Match packets that contain specified text |
dscp (integer: 0..63; Default: ) | Matches DSCP IP header field. |
dst-address (IP/netmask | IP range; Default: ) | Matches packets whose destination is equal to specified IP or falls into a specified IP range. |
dst-address-list (name; Default: ) | Matches destination address of a packet against user-defined address list. |
dst-address-type (unicast | local | broadcast | multicast; Default: ) | Matches destination address type:
|
dst-limit (integer[/time],integer,dst-address | dst-port | src-address[/time]; Default: ) | Matches packets until a given rate is exceeded. Rate is defined as packets per time interval. As opposed to the limit matcher, every flow has its own limit. Flow is defined by a mode parameter. Parameters are written in the following format: rate[/time],burst,mode[/expire] .
|
dst-port (integer[-integer]: 0..65535; Default: ) | List of destination port numbers or port number ranges |
icmp-options (integer:integer; Default: ) | Matches ICMP type: code fields |
in-bridge-port (name; Default: ) | Actual interface the packet has entered the router if the incoming interface is a bridge. Works only if use-ip-firewall is enabled in bridge settings. |
in-bridge-port-list (name; Default: ) | Set of interfaces defined in interface list. Works the same as in-bridge-port |
in-interface (name; Default: ) | Interface the packet has entered the router |
in-interface-list (name; Default: ) | Set of interfaces defined in interface list. Works the same as in-interface |
ingress-priority (integer: 0..63; Default: ) | Matches the priority of an ingress packet. Priority may be derived from VLAN, WMM, DSCP, or MPLS EXP bit. |
ipsec-policy (in | out, ipsec | none; Default: ) | Matches the policy used by IPsec. Value is written in the following format: direction, policy . The direction is Used to select whether to match the policy used for decapsulation or the policy that will be used for encapsulation.
For example, if a router receives an IPsec encapsulated Gre packet, then rule |
jump-target (name; Default: ) | Name of the target chain to jump to. Applicable only if action=jump |
limit (integer,time,integer; Default: ) | Matches packets up to a limited rate (packet rate or bit rate). A rule using this matcher will match until this limit is reached. Parameters are written in the following format: rate[/time],burst:mode .
|
log (yes | no; Default: no) | Add a message to the system log containing the following data: in-interface, out-interface, src-mac, protocol, src-ip:port->dst-ip:port, and length of the packet. |
log-prefix (string; Default: ) | Adds specified text at the beginning of every log message. Applicable if action=log or log=yes configured. |
nth (integer,integer; Default: ) | Matches every nth packet: nth=2,1 rule will match every first packet of 2, hence, 50% of all the traffic that is matched by the rule |
out-bridge-port (name; Default: ) | Actual interface the packet is leaving the router if the outgoing interface is a bridge. Works only if use-ip-firewall is enabled in bridge settings. |
out-bridge-port-list (name; Default: ) | Set of interfaces defined in interface list. Works the same as out-bridge-port |
out-interface (; Default: ) | Interface the packet is leaving the router |
out-interface-list (name; Default: ) | Set of interfaces defined in interface list. Works the same as out-interface |
packet-mark (no-mark | string; Default: ) | Matches packets marked via mangle facility with particular packet mark. If no-mark is set, the rule will match any unmarked packet. |
packet-size (integer[-integer]:0..65535; Default: ) | Matches packets of specified size or size range in bytes. |
per-connection-classifier (ValuesToHash:Denominator/Remainder; Default: ) | PCC matcher allows dividing traffic into equal streams with the ability to keep packets with a specific set of options in one particular stream. |
port (integer[-integer]: 0..65535; Default: ) | Matches if any (source or destination) port matches the specified list of ports or port ranges. Applicable only if protocol is TCP or UDP |
priority (integer: 0..63; Default:) | Matches the packet's priority after a new priority has been set. Priority may be derived from VLAN, WMM, DSCP, MPLS EXP bit, or from the priority that has been set using the set-priority action. |
protocol (name or protocol ID; Default: tcp) | Matches particular IP protocol specified by protocol name or number |
random (integer: 1..99; Default: ) | Matches packets randomly with a given probability |
reject-with (icmp-admin-prohibited | icmp-net-prohibited | icmp-protocol-unreachable | icmp-host-prohibited | icmp-network-unreachable | tcp-reset | icmp-host-unreachable | icmp-port-unreachable; Default: icmp-network-unreachable) | Specifies ICMP error to be sent back if the packet is rejected. Applicable if action=reject |
routing-mark (string; Default: ) | Matches packets marked by mangle facility with particular routing mark |
src-address (Ip/Netmask, Ip range; Default: ) | Matches packets whose source is equal to specified IP or falls into a specified IP range |
src-address-list (name; Default: ) | Matches source address of a packet against user-defined address list |
src-address-type (unicast | local | broadcast | multicast; Default: ) | {ta{tableMatches source address type:
|
src-port (integer[-integer]: 0..65535; Default: ) | List of source ports and ranges of source ports. Applicable only if a protocol is TCP or UDP |
src-mac-address (MAC address; Default: ) | Matches source MAC address of the packet |
tcp-flags (ack | cwr | ece | fin | psh | rst | syn | urg; Default: ) | Matches specified TCP flags
|
tcp-mss (integer[-integer]: 0..65535; Default: ) | Matches TCP MSS value of an IP packet |
time (time-time,sat | fri | thu | wed | tue | mon | sun; Default: ) | Allows to create a filter based on the packets' arrival time and date or, for locally generated packets, departure time and date |
tls-host (string; Default: ) | Allows matching HTTPS traffic based on TLS SNI hostname. Accepts GLOB syntax for wildcard matching. Note that the matcher will not be able to match the hostname if the TLS handshake frame is fragmented into multiple TCP segments (packets). |
/ipv6/firewall/filter/print/stats
To show additional read-only properties:
Property | Description |
---|---|
bytes (integer) | The total amount of bytes matched by the rule |
packets (integer) | The total amount of packets matched by the rule |
An example on how to properly secure your device you can find in our Building Your First Firewall article!