Manual:IP/Firewall/NAT: Difference between revisions
Jump to navigation
Jump to search
No edit summary |
No edit summary |
||
| Line 8: | Line 8: | ||
<br /> | <br /> | ||
There are two types of NAT: | There are two types of NAT: | ||
<ul> | |||
<ul class="bullets"> | |||
<li> <b>source NAT or srcnat.</b> This type of NAT is performed on packets that are originated from a natted network. A NAT router replaces the private source address of an IP packet with a new public IP address as it travels through the router. A reverse operation is applied to the reply packets travelling in the other direction. | |||
<li> <b>destination NAT or dstnat.</b> This type of NAT is performed on packets that are destined to the natted network. It is most comonly used to make hosts on a private network to be acceesible from the Internet. A NAT router performing dstnat replaces the destination IP address of an IP packet as it travel through the router towards a private network. | |||
</ul> | </ul> | ||
| Line 30: | Line 31: | ||
<tr> | <tr> | ||
<td><var><b>action</b></var> (<em>action name</em>; Default: <b>accept</b>)</td> | <td><var><b>action</b></var> (<em>action name</em>; Default: <b>accept</b>)</td> | ||
<td>Action to take if packet is matched by the rule: <ul> | <td>Action to take if packet is matched by the rule: | ||
<ul class="bullets"> | |||
<li> <var>accept</var> - accept the packet. Packet is not passed to next NAT rule. | |||
<li> <var>add-dst-to-address-list</var> - add destination address to [[Address list]] specified by <code>address-list</code> parameter | |||
<li> <var>add-src-to-address-list</var> - add source address to [[Address list]] specified by <code>address-list</code> parameter | |||
<li> <var>dst-nat</var> - replaces destination address and/or port of an IP packet to values specified by <code>to-addresses</code> and <code>to-ports</code> parameters | |||
<li> <var>jump</var> - jump to the user defined chain specified by the value of <code>jump-target</code> parameter | |||
<li> <var>log</var> - 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 <code>passthrough</code> | |||
<li> <var>masquerade</var> - replace source address of an IP packet to IP determined by routing facility. | |||
<li> <var>netmap</var> - creates a static 1:1 mapping of one set of IP addresses to another one. Often used to distribute public IP addresses to hosts on private networks | |||
<li> <var>passthrough</var> - ignore this rule and go to next one (useful for statistics). | |||
<li> <var>redirect</var> - replaces destination port of an IP packet to one specified by <code>to-ports</code> parameter | |||
<li> <var>return</var> - passes control back to the chain from where the jump took place | |||
<li> <var>same</var> - gives a particular client the same source/destination IP address from supplied range for each connection. This is most frequently used for services that expect the same client address for multiple connections from the same client | |||
<li> <var>src-nat</var> - replaces source address of an IP packet to values specified by <code>to-addresses</code> and <code>to-ports</code> parameters | |||
</ul> | </ul> | ||
</td> | </td> | ||
| Line 83: | Line 85: | ||
<td><var><b>connection-state</b></var> (<em>estabilished | invalid | new | related</em>; Default: <b></b>)</td> | <td><var><b>connection-state</b></var> (<em>estabilished | invalid | new | related</em>; Default: <b></b>)</td> | ||
<td>Interprets the connection tracking analysis data for a particular packet: | <td>Interprets the connection tracking analysis data for a particular packet: | ||
<ul> | <ul class="bullets"> | ||
<li> <var>established</var> - a packet which belongs to an existing connection | |||
<li> <var>invalid</var> - a packet which could not be identified for some reason | |||
<li> <var>new</var> - a packet which begins a new connection | |||
<li> <var>related</var> - 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 | |||
</ul> | </ul> | ||
</td> | </td> | ||
| Line 114: | Line 116: | ||
<td><var><b>dst-address-type</b></var> (<em>unicast | local | broadcast | multicast</em>; Default: <b></b>)</td> | <td><var><b>dst-address-type</b></var> (<em>unicast | local | broadcast | multicast</em>; Default: <b></b>)</td> | ||
<td>Matches destination address type: | <td>Matches destination address type: | ||
<ul> | <ul class="bullets"> | ||
<li> <var>unicast</var> - IP address used for point to point transmission | |||
<li> <var>local</var> - if dst-address is assigned to one of router's interfaces | |||
<li> <var>broadcast</var> - packet is sent to all devices in subnet | |||
<li> <var>multicast</var> - packet is forwarded to defined group of devices | |||
</ul> | </ul> | ||
</td> | </td> | ||
| Line 125: | Line 127: | ||
<td><var><b>dst-limit</b></var> (<em>integer,time,integer,dst-address | dst-port | src-address, time</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>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>. | <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> | <ul class="bullets"> | ||
<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> | </ul> | ||
</td> | </td> | ||
| Line 165: | Line 167: | ||
<td><var><b>ipv4-options</b></var> (<em>any | loose-source-routing | no-record-route | no-router-alert | no-source-routing | no-timestamp | none | record-route | router-alert | strict-source-routing | timestamp</em>; Default: <b></b>)</td> | <td><var><b>ipv4-options</b></var> (<em>any | loose-source-routing | no-record-route | no-router-alert | no-source-routing | no-timestamp | none | record-route | router-alert | strict-source-routing | timestamp</em>; Default: <b></b>)</td> | ||
<td>Matches IPv4 header options. | <td>Matches IPv4 header options. | ||
<ul> | <ul class="bullets"> | ||
<li> <var>any</var> - match packet with at least one of the ipv4 options | |||
<li> <var>loose-source-routing</var> - match packets with loose source routing option. This option is used to route the internet datagram based on information supplied by the source | |||
<li> <var>no-record-route</var> - match packets with no record route option. This option is used to route the internet datagram based on information supplied by the source | |||
<li> <var>no-router-alert</var> - match packets with no router alter option | |||
<li> <var>no-source-routing</var> - match packets with no source routing option | |||
<li> <var>no-timestamp</var> - match packets with no timestamp option | |||
<li> <var>record-route</var> - match packets with record route option | |||
<li> <var>router-alert</var> - match packets with router alter option | |||
<li> <var>strict-source-routing</var> - match packets with strict source routing option | |||
<li> <var>timestamp</var> - match packets with timestamp | |||
</ul> | </ul> | ||
</td> | </td> | ||
| Line 190: | Line 192: | ||
<td><var><b>limit</b></var> (<em>integer,time,integer</em>; Default: <b></b>)</td> | <td><var><b>limit</b></var> (<em>integer,time,integer</em>; Default: <b></b>)</td> | ||
<td>Matches packets if given pps limit is exceeded. Parameters are written in following format: <code>count,time,burst</code>. | <td>Matches packets if given pps limit is exceeded. Parameters are written in following format: <code>count,time,burst</code>. | ||
<ul> | <ul class="bullets"> | ||
<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> | </ul> | ||
</td> | </td> | ||
| Line 236: | Line 238: | ||
<td><var><b>psd</b></var> (<em>integer,time,integer,integer</em>; Default: <b></b>)</td> | <td><var><b>psd</b></var> (<em>integer,time,integer,integer</em>; Default: <b></b>)</td> | ||
<td>Attempts to detect TCP and UDP scans. Parameters are in following format <code>WeightThreshold, DelayThreshold, LopPortWeight, HighPortWeight</code> | <td>Attempts to detect TCP and UDP scans. Parameters are in following format <code>WeightThreshold, DelayThreshold, LopPortWeight, HighPortWeight</code> | ||
<ul> | <ul class="bullets"> | ||
<li> <b>WeightThreshold</b> - total weight of the latest TCP/UDP packets with different destination ports coming from the same host to be treated as port scan sequence | |||
<li> <b>DelayThreshold</b> - delay for the packets with different destination ports coming from the same host to be treated as possible port scan subsequence | |||
<li> <b>LowPortWeight</b> - weight of the packets with privileged (<=1024) destination port | |||
<li> <b>HighPortWeight</b> - weight of the packet with non-priviliged destination port | |||
</ul> | </ul> | ||
</td> | </td> | ||
| Line 268: | Line 270: | ||
<td> | <td> | ||
Matches source address type: | Matches source address type: | ||
<ul> | <ul class="bullets"> | ||
<li> <var>unicast</var> - IP address used for point to point transmission | |||
<li> <var>local</var> - if address is assigned to one of router's interfaces | |||
<li> <var>broadcast</var> - packet is sent to all devices in subnet | |||
<li> <var>multicast</var> - packet is forwarded to defined group of devices | |||
</ul> | </ul> | ||
</td> | </td> | ||
| Line 287: | Line 289: | ||
<td><var><b>tcp-flags</b></var> (<em>ack | cwr | ece | fin | psh | rst | syn | urg</em>; Default: <b></b>)</td> | <td><var><b>tcp-flags</b></var> (<em>ack | cwr | ece | fin | psh | rst | syn | urg</em>; Default: <b></b>)</td> | ||
<td>Matches specified TCP flags | <td>Matches specified TCP flags | ||
<ul> | <ul class="bullets"> | ||
<li> <var>ack</var> - acknowledging data | |||
<li> <var>cwr</var> - congestion window reduced | |||
<li> <var>ece</var> - ECN-echo flag (explicit congestion notification) | |||
<li> <var>fin</var> - close connection | |||
<li> <var>psh</var> - push function | |||
<li> <var>rst</var> - drop connection | |||
<li> <var>syn</var> - new connection | |||
<li> <var>urg</var> - urgent data | |||
</ul> | </ul> | ||
</td> | </td> | ||
| Line 368: | Line 370: | ||
[[Category:Manual]] | [[Category:Manual]] | ||
Revision as of 09:38, 15 October 2009
Summary
Sub-menu: /ip firewall nat
Network Address Translation is an Internet standard that allows hosts on local area networks to use one set of IP addresses for internal communications and another set of IP addresses for external communications. A LAN that uses NAT is referred as natted network. For NAT to function, there should be a NAT gateway in each natted network. The NAT gateway (NAT router) performs IP address rewriting on the way a packet travel from/to LAN.
There are two types of NAT:
- source NAT or srcnat. This type of NAT is performed on packets that are originated from a natted network. A NAT router replaces the private source address of an IP packet with a new public IP address as it travels through the router. A reverse operation is applied to the reply packets travelling in the other direction.
- destination NAT or dstnat. This type of NAT is performed on packets that are destined to the natted network. It is most comonly used to make hosts on a private network to be acceesible from the Internet. A NAT router performing dstnat replaces the destination IP address of an IP packet as it travel through the router towards a private network.
Hosts behind a NAT-enabled router do not have true end-to-end connectivity. Therefore some Internet protocols might not work in scenarios with NAT. Services that require the initiation of TCP connection from outside the private network or stateless protocols such as UDP, can be disrupted. Moreover, some protocols are inherently incompatible with NAT, a bold example is AH protocol from the IPsec suite.
To overcome these limitations RouterOS includes a number of so-called NAT helpers, that enable NAT traversal for various protocols.
Properties
| Property | Description |
|---|---|
| action (action name; Default: accept) | Action to take if packet is matched by the rule:
|
| 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 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:
|
| 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:
|
| 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.
|
| 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: ) | |
| 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 (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 if given pps limit is exceeded. Parameters are written in following format: count,time,burst.
|
| 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 (name; Default: ) | Actual interface the packet is leaving the router, if outgoing interface is bridge |
| out-interface (; Default: ) | Interface the packet is leaving the router |
| packet-mark (string; Default: ) | Matches packets marked via mangle facility with particular packet mark |
| 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 to divide traffic into equal streams with ability to keep packets with 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 |
| 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 following format WeightThreshold, DelayThreshold, LopPortWeight, HighPortWeight
|
| random (integer: 1..99; Default: ) | Matches packets randomly with given probability. |
| routing-mark (string; Default: ) | Matches packets marked by mangle facility with particular routing mark |
| same-not-by-dst (yes | no; Default: ) | Specifies whether to take into account or not destination IP address when selecting a new source IP address. Applicable if action=same |
| 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:
|
| 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
|
| tcp-mss (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 filter based on the packets' arrival time and date or, for locally generated packets, departure time and date |
| to-addresses (IP address[-IP address]; Default: 0.0.0.0) | Replace original address with specified one. Applicable if action is dst-nat, netmap, same, src-nat |
| to-ports (integer[-integer]: 0..255; Default: ) | Replace original port with specified one. Applicable if action is dst-nat, redirect, netmap, same, src-nat |
| ttl (integer: 0..255; Default: ) | Matches packets TTL value |
Stats
/ip firewall nat print stats will show additional read-only properties
| Property | Description |
|---|---|
| bytes (integer;) | Total amount of bytes matched by the rule |
| packets (integer;) | Total amount of packets matched by the rule |
Menu specific commands
| Property | Description |
|---|---|
| reset-counters (id;) | Reset statistics counters for specified firewall rules. |
| reset-counters-all (;) | Reset statistics counters for all firewall rules. |
Basic examples