Overview
/ip firewall
The firewall implements packet filtering and thereby provides security functions that are used to manage data flow to, from and through the router. Along with the Network Address Translation, it serves as a tool for preventing unauthorized access to directly attached networks and the router itself as well as a filter for outgoing traffic. Network firewalls keep outside threats away from sensitive data available inside the network. Whenever different networks are joined together, there is always a threat that someone from outside of your network will break into your LAN. Such break-ins may result in private data being stolen and distributed, valuable data being altered or destroyed, or entire hard drives being erased. Firewalls are used as a means of preventing or minimizing the security risks inherent in connecting to other networks. Properly configured firewall plays a key role in efficient and secure network infrastructure deployment.
Firewall filter
Chains
The firewall operates by means of firewall rules. Each rule consists of two parts - the matcher which matches traffic flow against given conditions and the action which defines what to do with the matched packet.
There are three predefined chains, which cannot be deleted:
- input - used to process packets entering the router through one of the interfaces with the destination IP address which is one of the router's addresses. Packets passing through the router are not processed against the rules of the input chain
- forward - used to process packets passing through the router
- output - used to process packets originated from the router and leaving it through one of the interfaces. Packets passing through the router are not processed against the rules of the output chain
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.
Custom chain
A packet should be matched against the IP address:port pair. Of course, it could be achieved by adding as many rules with IP address:port match as required to the forward chain, but a better way could be to add one rule that matches traffic from a particular IP address, e.g.: /ip firewall filter add src-address=1.1.1.2/32 jump-target="mychain" and in case of successful match passes control over the IP packet to some other chain, id est mychain in this example. Then rules that perform matching against separate ports can be added to mychain chain without specifying the IP addresses.
Properties
Property | Description |
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action (action name; Default: accept) | Action to take if packet is matched by the rule:
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address-list (string; Default: ) | Name of the address list to be used. Applicable if action is add-dst-to-address-list or add-src-to-address-list |
address-list-timeout (time; Default: 00:00:00) | 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 actionsValue of 00:00:00 will leave the address in the address list forever |
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 a 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 src-nat`ted, dst-nat`ted 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. Read more >> |
connection-state (established | invalid | new | related | untracked; Default: ) | Interprets the connection tracking analytics data for a particular packet:
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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 /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; Default: ) | Matches destination address type:
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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: count[/time],burst,mode[/expire] .
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dst-port (integer[-integer]: 0..65535; Default: ) | List of destination port numbers or port number ranges |
fragment (yes|no; Default: ) | Matches fragmented packets. First (starting) fragment does not count. If connection tracking is enabled there will be no fragments as 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.
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icmp-options (integer:integer; Default: ) | Matches ICMP type:code fields |
in-bridge-port (name; Default: ) | Actual interface the packet has entered the router if incoming interface is bridge. Works only if use-ip-firewall is enabled in bridge settings. |
in-bridge-port-list (name; Default: ) | Set of interfaces defined in the 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 the 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 . 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.
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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 the layer7 protocol menu. |
limit (integer,time,integer; Default: ) | Matches packets up to a limited rate (packet rate or bit rate). Rule using this matcher will match until this limit is reached. Parameters are written in the following format: count[/time],burst:mode .
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log-prefix (string; Default: ) | Adds specified text at the beginning of every log message. Applicable if action=log |
nth (integer,integer; Default: ) | Matches every nth packet. |
out-bridge-port (name; Default: ) | Actual interface the packet is leaving the router if the outgoing interface is bridge. Works only if use-ip-firewall is enabled in bridge settings. |
out-bridge-port-list (name; Default: ) | Set of interfaces defined in the 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 the 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 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 |
psd (integer,time,integer,integer; Default: ) | Attempts to detect TCP and UDP scans. Parameters are in the following format WeightThreshold, DelayThreshold, LowPortWeight, HighPortWeight
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random (integer: 1..99; Default: ) | Matches packets randomly with 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 the ICMP error to be sent back if a packet is rejected. Applicable if action=reject |
routing-table (string; Default: ) | Matches packets which destination address is resolved in specific a routing table. More details can be found in the Routing Table Matcher page |
routing-mark (string; Default: ) | Matches packets marked by mangle facility with particular routing mark |
src-address (Ip/Netmaks, Ip range; Default: ) | Matches packets which source is equal to specified IP or falls into 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: ) | Matches source address type:
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src-port (integer[-integer]: 0..65535; Default: ) | List of source ports and ranges of source ports. Applicable only if 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
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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 TLS handshake frame is fragmented into multiple TCP segments (packets). |
ttl (integer: 0..255; Default: ) | Matches packets TTL value |
Stats
/ip firewall filter print stats
Will show additional read-only properties
Property | Description |
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bytes (integer) | Total amount of bytes matched by the rule |
packets (integer) | Total amount of packets matched by the rule |
By default, print is equivalent to print static and shows only static rules.
[admin@mikrotik] /ip firewall mangle> print stats Flags: X - disabled, I - invalid, D - dynamic # CHAIN ACTION BYTES PACKETS 0 prerouting mark-routing 17478158 127631 1 prerouting mark-routing 782505 4506
To print also dynamic rules use print all.
[admin@mikrotik] /ip firewall mangle> print all stats Flags: X - disabled, I - invalid, D - dynamic # CHAIN ACTION BYTES PACKETS 0 prerouting mark-routing 17478158 127631 1 prerouting mark-routing 782505 4506 2 D forward change-mss 0 0 3 D forward change-mss 0 0 4 D forward change-mss 0 0 5 D forward change-mss 129372 2031
Or to print only dynamic rules use print dynamic
[admin@mikrotik] /ip firewall mangle> print stats dynamic Flags: X - disabled, I - invalid, D - dynamic # CHAIN ACTION BYTES PACKETS 0 D forward change-mss 0 0 1 D forward change-mss 0 0 2 D forward change-mss 0 0 3 D forward change-mss 132444 2079