...
To combat IPv4 address exhaustion, a new RFC 6598 was deployed. The idea is to use shared 100.64.0.0/10 address space inside the carrier's network and performing perform NAT on the carrier's edge router to a single public IP or public IP range.
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Service providers may be required to do logging log of MAPed addresses, in a large CGN deployed network that may be a problem. Fortunately, RFC 7422 suggests a way to manage CGN translations in such a way as to significantly reduce the amount of logging required while providing traceability for abuse response.
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- the client sends a packet with a source IP address of 192.168.88.1 to a destination IP address of 172.16.16.1 on port 443 to request some web resourceresources;
- the router destination NAT`s the packet to 10.0.0.3 and replaces the destination IP address in the packet accordingly. The source IP address stays the same: 192.168.88.1;
- the server replies to the client's request and the reply packet have a source IP address of 10.0.0.3 and a destination IP address of 192.168.88.1.
- the router determines that the packet is part of a previous connection and undoes the destination NAT, and puts the original destination IP address into the source IP address field. The destination IP address is 192.168.88.1, and the source IP address is 172.16.16.1;
- The client receives the reply packet it expects, and the connection is established;
...
The issue occurs, when a client on the same internal network as the webserver requests a connection to the web server's public IP address, and the connection breaks:
- the client sends a packet with a source IP address of 10.0.0.2 to a destination IP address of address of 172.16.16.1 on port 443 to request some web resourceresources;
- the router destination NATs the packet to 10.0.0.3 and replaces the destination IP address in the packet accordingly. The source IP address stays the same: 10.0.0.2;
- the server replies to the client's request. However, the source IP address of the request is on the same subnet as the webserver. The web server does not send the reply back to the router but sends it back directly to 10.0.0.2 with a source IP address in the reply of 10.0.0.3;
- The client receives the reply packet, but it discards it because it expects a packet back from 172.16.16.1, and not from 10.0.0.3;
...
| Code Block | ||
|---|---|---|
| ||
/ip firewall nat add action=masquerade chain=srcnat dst-address=10.0.0.3 out-interface=LAN protocol=tcp src-address=10.0.0.0/24 |
After configured configuring the rule above:
- the client sends a packet with a source IP address of 10.0.0.2 to a destination IP address of address of 172.16.16.1 on port 443 to request some web resourceresources;
- the router destination NATs the packet to 10.0.0.3 and replaces the destination IP address in the packet accordingly. It also source NATs the packet and replaces the source IP address in the packet with the IP address on its LAN interface. The destination IP address is 10.0.0.3, and the source IP address is 10.0.0.1;
- the webserver web server replies to the request and sends the reply with a source IP address of 10.0.0.3 back to the router's LAN interface IP address of 10.0.0.1;
- the router determines that the packet is part of a previous connection and undoes both the source and destination NAT, and puts the original destination IP address of 1.1.1.1 into the source IP address field, and the original source IP address of 172.16.16.1 into the destination IP address field
IPv4
Properties
| Property | Description |
|---|---|
| action (action name; Default: accept) | Action to take if a 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 (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 |
| 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 |
| 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-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 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 pps PPS limit is exceeded. As opposed to the limit matcher, every destination IP address/destination port has its own limit. Parameters are written in the following format: count[/time],burst,mode[/expire].
|
| dst-port (integer[-integer]: 0..65535; Default: ) | List of destination port numbers or port number ranges in format Range[,Port], for example, dst-port=123-345,456-678 |
| 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 |
| in-interface (name; Default: ) | Interface the packet has entered the router |
| ingress-priority (integer: 0..63; Default: ) | Matches ingress the priority of the packet. Priority may be derived from VLAN, WMM or MPLS EXP bit. |
| ipsec-policy (in | out, ipsec | none; Default: ) | Matches the policy used by IpSecIPSec. 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 until a given PPS limit is exceeded. Parameters are written in the following format: count[/time],burst.
|
| 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. |
| out-bridge-port (name; Default: ) | Actual interface the packet is leaving the router if the outgoing interface is a bridge |
| out-interface (; Default: ) | Interface the packet is leaving the router |
| 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 |
| 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 |
| 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 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: ) | Matches 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-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 |
| to-addresses (IP address[-IP address]; Default: 0.0.0.0) | Replace the original address with the specified one. Applicable if action is dst-nat, netmap, same, src-nat |
| to-ports (integer[-integer]: 0..65535; Default: ) | Replace the original port with the specified one. Applicable if action is dst-nat, redirect, masquerade, netmap, same, src-nat |
| ttl (integer: 0..255; Default: ) | Matches packets TTL value |
...
| Code Block | ||
|---|---|---|
| ||
[admin@MikroTik] > ip firewall nat print stats all Flags: X - disabled, I - invalid, D - dynamic # CHAIN ACTION BYTES PACKETS 0 srcnat masquerade 265 659 987 |
IPv6
NAT66 is supported since RouterOS v7.1.
| Code Block | ||
|---|---|---|
| ||
ipv6/firewall/nat/ |
Properties
| Property | Description |
|---|---|
| action (action name; Default: accept) | Action to take if a 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 (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 |
| 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 |
| 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 /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 PPS limit is exceeded. As opposed to the limit matcher, every destination IP address/destination port has its own limit. Parameters are written in the following format: count[/time],burst,mode[/expire].
|
| dst-port (integer[-integer]: 0..65535; Default: ) | List of destination port numbers or port number ranges in format Range[,Port], for example, dst-port=123-345,456-678 |
| 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 |
| 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 ingress the priority of the packet. Priority may be derived from VLAN, WMM 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 |
| layer7-protocol (name; Default: ) | Layer7 filter name defined in layer7 protocol menu. |
| limit (integer,time,integer; Default: ) | Matches packets until a given PPS limit is exceeded. Parameters are written in the following format: count[/time],burst.
|
| 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. |
| out-bridge-port (name; Default: ) | Actual interface the packet is leaving the router if the outgoing interface is a bridge |
| 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 |
| protocol (name or protocol ID; Default: tcp) | Matches particular IP protocol specified by protocol name or number |
| 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. |
| random (integer: 1..99; Default: ) | Matches packets randomly with a given probability |
| routing-mark (string; Default: ) | Matches packets marked by mangle facility with particular routing mark |
| src-address (Ip/Netmaks, 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: ) | Matches 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. |
| tcp-flags (ack | cwr | ece | fin | psh | rst | syn | urg; Default: ) | Matches specified TCP flags
|
| src-mac-address (MAC address; Default: ) | Matches source MAC address of the packet |
| 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 |
| to-addresses (IP address[-IP address]; Default: 0.0.0.0) | Replace the original address with the specified one. Applicable if action is dst-nat, netmap, same, src-nat |
| to-ports (integer[-integer]: 0..65535; Default: ) | Replace the original port with the specified one. Applicable if action is dst-nat, redirect, masquerade, netmap, same, src-nat |
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 |
To show additional read-only properties:
| Code Block | ||
|---|---|---|
| ||
ipv6/firewall/nat/print stats |