Manual:IP/Firewall/Filter: Difference between revisions

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     <td><var><b>dst-limit</b></var> (<em></em>; Default: <b></b>)</td>
     <td><var><b>dst-limit</b></var> (<em>integer,time,integer,dst-address | dst-port | src-address, time</em>; Default: <b></b>)</td>
     <td></td>
     <td>Matches packets if given pps limit is exceeded. As opposed to the <var>limit</var> matcher, every destination IP address / destination port has it's own limit. Parameters are written in following format: <code>count,time,burst,mode,expire</code>.
<ul>
:<li><b>count</b> - maximum average packet rate measured in packets per <code>time</code> interval
:<li><b>time</b> - specifies the time interval in which the packet rate is measured
:<li><b>burst</b> - number of packets which are not counted by packet rate
:<li><b>mode</b> - the classifier for packet rate limiting
:<li><b>expire</b> - specifies interval after which recored ip address /port will be deleted
</ul>
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     <td><var><b>dst-port</b></var> (<em></em>; Default: <b></b>)</td>
     <td><var><b>dst-port</b></var> (<em>integer: 0..65535</em>; Default: <b></b>)</td>
     <td></td>
     <td>List of destination port numbers or port number ranges</td>
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     <td><var><b>fragment</b></var> (<em></em>; Default: <b></b>)</td>
     <td><var><b>fragment</b></var> (<em>yes|no</em>; Default: <b></b>)</td>
     <td></td>
     <td>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</td>
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     <td><var><b>hotspot</b></var> (<em></em>; Default: <b></b>)</td>
     <td><var><b>hotspot</b></var> (<em>auth | from-client | http | local-dst | to-client</em>; Default: <b></b>)</td>
     <td></td>
     <td></td>
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     <td><var><b>icmp-options</b></var> (<em></em>; Default: <b></b>)</td>
     <td><var><b>icmp-options</b></var> (<em>integer:integer</em>; Default: <b></b>)</td>
     <td></td>
     <td>Matches ICMP type:code fileds</td>
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     <td><var><b>in-bridge-port</b></var> (<em></em>; Default: <b></b>)</td>
     <td><var><b>in-bridge-port</b></var> (<em>name</em>; Default: <b></b>)</td>
     <td></td>
     <td>Actual interface the packet has entered the router, if incoming interface is bridge</td>
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     <td><var><b>in-interface</b></var> (<em></em>; Default: <b></b>)</td>
     <td><var><b>in-interface</b></var> (<em>name</em>; Default: <b></b>)</td>
     <td></td>
     <td>Interface the packet has entered the router</td>
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     <td><var><b>ingress-priority</b></var> (<em></em>; Default: <b></b>)</td>
     <td><var><b>ingress-priority</b></var> (<em>integer: 0..63</em>; Default: <b></b>)</td>
     <td></td>
     <td>Matches ingress priority of the packet. Priority may be derived from VLAN, WMM or MPLS EXP bit. [[WMM | Read more>]]</td>
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     <td><var><b>jump-target</b></var> (<em></em>; Default: <b></b>)</td>
     <td><var><b>jump-target</b></var> (<em>name</em>; Default: <b></b>)</td>
     <td></td>
     <td>Name of the target chain to jump to. Applicable only if <code>action=jump</code></td>
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     <td><var><b>layer7-protocol</b></var> (<em></em>; Default: <b></b>)</td>
     <td><var><b>layer7-protocol</b></var> (<em>name</em>; Default: <b></b>)</td>
     <td></td>
     <td>Layer7 filter name defined in [[layer7 protocol menu]].</td>
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     <td><var><b>limit</b></var> (<em></em>; Default: <b></b>)</td>
     <td><var><b>limit</b></var> (<em>integer,time,integer</em>; Default: <b></b>)</td>
     <td></td>
     <td>Matches packets if given pps limit is exceeded. Parameters are written in following format: <code>count,time,burst</code>.
<ul>
:<li><b>count</b> - maximum average packet rate measured in packets per <code>time</code> interval
:<li><b>time</b> - specifies the time interval in which the packet rate is measured
:<li><b>burst</b> - number of packets which are not counted by packet rate
</ul>
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     <td><var><b>log-prefix</b></var> (<em></em>; Default: <b></b>)</td>
     <td><var><b>log-prefix</b></var> (<em>string</em>; Default: <b></b>)</td>
     <td></td>
     <td>Adds specified text at the beginning of every log message. Applicable if <code>action=log</code></td>
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     <td><var><b>nth</b></var> (<em></em>; Default: <b></b>)</td>
     <td><var><b>nth</b></var> (<em>integer,integer</em>; Default: <b></b>)</td>
     <td></td>
     <td>Matches every nth packet. [[NTH_in_RouterOS_3.x | Read more]]</td>
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Revision as of 10:14, 29 September 2009

Summary

Sub-menu: /ip firewall filter


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 infrastrure deployment.


MikroTik RouterOS has very powerful firewall implementation with features including:

  • stateful packet inspection
  • Layer-7 protocol detection
  • peer-to-peer protocols filtering
  • traffic classification by:
  • source MAC address
  • IP addresses (network or list) and address types (broadcast, local, multicast, unicast)
  • port or port range
  • IP protocols
  • protocol options (ICMP type and code fields, TCP flags, IP options and MSS)
  • interface the packet arrived from or left through
  • internal flow and connection marks
  • DSCP byte
  • packet content
  • rate at which packets arrive and sequence numbers
  • packet size
  • packet arrival time
  • and much more!

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.

Firewall filtering rules are grouped together in chains. It allows a packet to be matched against one common criterion in one chain, and then passed over for processing against some other common criteria to another chain. For example 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 successfull 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.

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

Packet flow diagrams illustrate how packets are processed in RouterOS.

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 chain, then it is accepted.


Properties

Property Description
action (action name; Default: accept) Action to take if packet is matched by the rule:
  • accept - accept the packet. Packet is not passed to next firewall rule.
  • add-dst-to-address-list - add destination address to Address list specified by address-list parameter
  • add-src-to-address-list - add source address to Address list specified by address-list parameter
  • drop - silently drop the packet
  • jump - jump to the user defined chain specified by the value of jump-target parameter
  • log - add a message to the system log containing following data: in-interface, out-interface, src-mac, protocol, src-ip:port->dst-ip:port and length of the packet. After packet is matched it is passed to next rule in the list, similar as passthrough
  • passthrough - ignore this rule and go to next one (useful for statistics).
  • reject - drop the packet and send an ICMP reject message
  • tarpit - captures and holds TCP connections (replies with SYN/ACK to the inbound TCP SYN packet)
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 actions
Value 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 transfered through the particular connection. 0 - means infinity, for example connection-bytes=2000000-0 means that the rule matches if more than 2MB has been transfered through the relevant connection
connection-limit (integer,netmaks; Default: ) Restrict connection limit per address or address block/td>
connection-mark (string; Default: ) Matches packets marked via mangle facility with particular connection mark
connection-rate (Integer 0..4294967295; Default: ) Connection Rate is a firewall matcher that allow to capture traffic based on present speed of the connection. more>
connection-state (estabilished | invalid | new | related; Default: ) Interprets the connection tracking analysis data for a particular packet:
  • established - a packet which belongs to an existing connection
  • invalid - a packet which could not be identified for some reason
  • new - a packet which begins a new connection
  • related - a packet which is related to, but not part of an existing connection, such as ICMP errors or a packet which begins FTP data connection
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:
  • unicast - IP address used for point to point transmission
  • local - if dst-address is assigned to one of router's interfaces
  • broadcast - packet is sent to all devices in subnet
  • multicast - packet is forwarded to defined group of devices
dst-limit (integer,time,integer,dst-address | dst-port | src-address, time; Default: ) Matches packets if given pps limit is exceeded. As opposed to the limit matcher, every destination IP address / destination port has it's own limit. Parameters are written in following format: count,time,burst,mode,expire.
  • count - maximum average packet rate measured in packets per time interval
  • time - specifies the time interval in which the packet rate is measured
  • burst - number of packets which are not counted by packet rate
  • mode - the classifier for packet rate limiting
  • expire - specifies interval after which recored ip address /port will be deleted
dst-port (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: )
icmp-options (integer:integer; Default: ) Matches ICMP type:code fileds
in-bridge-port (name; Default: ) Actual interface the packet has entered the router, if incoming interface is bridge
in-interface (name; Default: ) Interface the packet has entered the router
ingress-priority (integer: 0..63; Default: ) Matches ingress priority of the packet. Priority may be derived from VLAN, WMM or MPLS EXP bit. Read more>
ipv4-options (; Default: )
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 if given pps limit is exceeded. Parameters are written in following format: count,time,burst.
  • count - maximum average packet rate measured in packets per time interval
  • time - specifies the time interval in which the packet rate is measured
  • burst - number of packets which are not counted by packet rate
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. Read more
out-bridge-port (; Default: )
out-interface (; Default: )
p2p (; Default: )
packet-mark (; Default: )
packet-size (; Default: )
per-connection-classifier (; Default: )
port (; Default: )
protocol (; Default: )
psd (; Default: )
random (; Default: )
reject-with (; Default: )
routing-mark (; Default: )
src-address (; Default: )
src-address-list (; Default: )
src-address-type (; Default: )
src-port (; Default: )
tcp-flags (; Default: )
tcp-mss (; Default: )
time (; Default: )
ttl (; Default: )

Stats

Basic examples