پاسخ : معرفی و نصب میکروتیک
NAT:
NAT یا Network Address Translation یک استاندارد در اینترنت است که به کامپیوتر های داحل یک شبکه این اجازه را می دهد که از یک رنج IP برای ارتباط داخلی و از یک رنج دیکر برای ارتباط خارجی استفاده کنند. به شبکه داحلی که از NAT استفاده می کند اصطلاحا Natted Network می گویند. برای ایجاد NAT باید در شبکه داخلی یک عدد NAT gateway داشته باشیم که ترجمه آدرسها در آن صورت گیرد.
در کل 2 نوع NAT وجود دارد
· SRCNAT یا Source Nat :
از این فرم Nat وقتی استفاده میکنیم که می خواهیم IP های Invalid یک شبکه داخلی یا Natted Network را به یک Valid IP ترجمه کنیم.در این حالت هر پکتی که به gateway برسد IP آن به یک Valid IP ترجمه گشته و بر روی اینترنت ارسال می شود. عکس این عمل برای پکت هایی که به پکت های قبلی Reply می شوند صادق است و عکس این عمل صورت میگیرد.
· DSTNAT یا Destination Nat :
این فرم NAT را وقتی انجام می دهیم که بخواهیم یک شبکه private را برای شبکه public خود قابل دسترسی قرار دهیم. در این عمل Valid IP خود را به Invalid IP ترجمه میکنیم.
Redirect و Masquerade
Redirect و Masquerade یک نوع خاص dstnat و srcnat است. Redirect یک نوع از dstnat است که نیازی به تعریف to-address ندارد و تنها شناساندن اینترفیس ورودی کافی است و Masquerade یک نوع srcnat است که نیازی به تعریف to-address ندارد و تنها معرفی یک اینترفیس خروجی کافی است. در این حالات دیگر فرقی ندارد که چه IP به اینترفیس ها متصل میگردد هر IP در رنج IP های add شده به اینترفیس عمل می کند. در Redirect فیلد to-port برای فرستادن کل ترافیک به یک پورت خاص است که بیشتر برای اعمالی نظیر web-***** استفاده می شود.
Property Description
action (accept | add-dst-to-address-list | add-src-to-address-list | dst-nat | jump | log | masquerade | netmap | passthrough | redirect | return | same | src-nat; default: accept) - action to undertake if the packet matches the rule
accept - accepts the packet. No action is taken, i.e. the packet is passed through and no more rules are applied to it
add-dst-to-address-list - adds destination address of an IP packet to the address list specified by address-list parameter
add-src-to-address-list - adds source address of an IP packet to the address list specified by address-list parameter
dst-nat - replaces destination address of an IP packet to values specified by to-addresses and to-ports parameters
jump - jump to the chain specified by the value of the jump-target parameter
log - each match with this action will add a message to the system log
masquerade - replaces source address of an IP packet to an automatically determined by the routing facility IP address
netmap - 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
passthrough - ignores this rule goes on to the next one
redirect - replaces destination address of an IP packet to one of the router's local addresses
return - passes control back to the chain from where the jump took place
same - 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
src-nat - replaces source address of an IP packet to values specified by to-addresses and to-ports parameters
address-list (name) - specifies the name of the address list to collect IP addresses from rules having action=add-dst-to-address-list or action=add-src-to-address-list actions. These address lists could be later used for packet matching
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
00:00:00 - leave the address in the address list forever
chain (dstnat | srcnat | name) - specifies the chain to put a particular rule into. As the different traffic is passed through different chains, always be careful in choosing the right chain for a new rule. If the input does not match the name of an already defined chain, a new chain will be created
dstnat - a rule placed in this chain is applied before routing. The rules that replace destination addresses of IP packets should be placed there
srcnat - a rule placed in this chain is applied after routing. The rules that replace the source addresses of IP packets should be placed there
comment (text) - a descriptive comment for the rule. A comment can be used to identify rules form scripts
connection-bytes (integer-integer) - matches packets only if a given amount of bytes has been transfered through the particular connection
0 - means infinity, exempli gratia: connection-bytes=2000000-0 means that the rule matches if more than 2MB has been transfered through the relevant connection
connection-limit (integer,netmask) - restrict connection limit per address or address block
connection-mark (name) - matches packets marked via mangle facility with particular connection mark
connection-type (ftp | gre | h323 | irc | mms | pptp | quake3 | tftp) - 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 (text) - the text packets should contain in order to match the rule
dst-address (IP address/netmask | IP address-IP address) - specifies the address range an IP packet is destined to. Note that console converts entered address/netmask value to a valid network address, i.e.:1.1.1.1/24 is converted to 1.1.1.0/24
dst-address-list (name) - matches destination address of a packet against user-defined address list
dst-address-type (unicast | local | broadcast | multicast) - matches destination address type of the IP packet, one of the:
unicast - IP addresses used for one point to another point transmission. There is only one sender and one receiver in this case
local - matches addresses assigned to router's interfaces
broadcast - the IP packet is sent from one point to all other points in the IP subnetwork
multicast - this type of IP addressing is responsible for transmission from one or more points to a set of other points
dst-limit (integer/time{0,1},integer,dst-address | dst-port | src-address{+},time{0,1}) - limits the packet per second (pps) rate on a per destination IP or per destination port base. As opposed to the limit match, every destination IP address / destination port has it's own limit. The options are as follows (in order of appearance):
Count - maximum average packet rate, measured in packets per second (pps), unless followed by Time option
Time - specifies the time interval over which the packet rate is measured
Burst - number of packets to match in a burst
Mode - the classifier(-s) for packet rate limiting
Expire - specifies interval after which recorded IP addresses / ports will be deleted
dst-port (integer: 0..65535-integer: 0..65535{*}) - destination port number or range
hotspot (multiple choice: from-client | auth | local-dst) - matches packets received from clients against various Hot-Spot. All values can be negated
from-client - true, if a packet comes from HotSpot client
auth - true, if a packet comes from authenticted client
local-dst - true, if a packet has local destination IP address
icmp-options (integer:integer) - matches ICMP Type:Code fields
in-interface (name) - interface the packet has entered the router through
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) - match ipv4 header options
any - match packet with at least one of the ipv4 options
loose-source-routing - match packets with loose source routing option. This option is used to route the internet datagram based on information supplied by the source
no-record-route - match packets with no record route option. This option is used to route the internet datagram based on information supplied by the source
no-router-alert - match packets with no router alter option
no-source-routing - match packets with no source routing option
no-timestamp - match packets with no timestamp option
record-route - match packets with record route option
router-alert - match packets with router alter option
strict-source-routing - match packets with strict source routing option
timestamp - match packets with timestamp
jump-target (dstnat | srcnatname) - name of the target chain to jump to, if the action=jump is used
limit (integer/time{0,1},integer) - restricts packet match rate to a given limit. Usefull to reduce the amount of log messages
Count - maximum average packet rate, measured in packets per second (pps), unless followed by Time option
Time - specifies the time interval over which the packet rate is measured
Burst - number of packets to match in a burst
log-prefix (text) - all messages written to logs will contain the prefix specified herein. Used in conjunction with action=log
nth (integer,integer: 0..15,integer{0,1}) - match a particular Nth packet received by the rule. One of 16 available counters can be used to count packets
Every - match every Every+1th packet. For example, if Every=1 then the rule matches every 2nd packet
Counter - specifies which counter to use. A counter increments each time the rule containing nth match matches
Packet - match on the given packet number. The value by obvious reasons must be between 0 and Every. If this option is used for a given counter, then there must be at least Every+1 rules with this option, covering all values between 0 and Every inclusively.
out-interface (name) - interface the packet is leaving the router through
packet-mark (text) - matches packets marked via mangle facility with particular packet mark
packet-size (integer: 0..65535-integer: 0..65535{0,1}) - matches packet of the specified size or size range in bytes
Min - specifies lower boundary of the size range or a standalone value
Max - specifies upper boundary of the size range
phys-in-interface (name) - matches the bridge port physical input device added to a bridge device. It is only useful if the packet has arrived through the bridge
phys-out-interface (name) - matches the bridge port physical output device added to a bridge device. It is only useful if the packet will leave the router through the bridge
protocol (ddp | egp | encap | ggp | gre | hmp | icmp | idrp-cmtp | igmp | ipencap | ipip | ipsec-ah | ipsec-esp | iso-tp4 | ospf | pup | rdp | rspf | st | tcp | udp | vmtp | xns-idp | xtp | integer) - matches particular IP protocol specified by protocol name or number. You should specify this setting if you want to specify ports
psd (integer,time,integer,integer) - attempts to detect TCP and UDP scans. It is advised to assign lower weight to ports with high numbers to reduce the frequency of false positives, such as from passive mode FTP transfers
WeightThreshold - total weight of the latest TCP/UDP packets with different destination ports coming from the same host to be treated as port scan sequence
DelayThreshold - delay for the packets with different destination ports coming from the same host to be treated as possible port scan subsequence
LowPortWeight - weight of the packets with privileged (<=1024) destination port
HighPortWeight - weight of the packet with non-priviliged destination port
random (integer) - match packets randomly with given propability
routing-mark (name) - matches packets marked by mangle facility with particular routing mark
same-not-by-dst (yes | no) - specifies whether to account or not to account for destination IP address when selecting a new source IP address for packets matched by rules with action=same
src-address (IP address/netmask | IP address-IP address) - specifies the address range an IP packet is originated from. Note that console converts entered address/netmask value to a valid network address, i.e.:1.1.1.1/24 is converted to 1.1.1.0/24
src-address-list (name) - matches source address of a packet against user-defined address list
src-address-type (unicast | local | broadcast | multicast) - matches source address type of the IP packet, one of the:
unicast - IP addresses used for one point to another point transmission. There is only one sender and one receiver in this case
local - matches addresses assigned to router's interfaces
broadcast - the IP packet is sent from one point to all other points in the IP subnetwork
multicast - this type of IP addressing is responsible for transmission from one or more points to a set of other points
src-mac-address (MAC address) - source MAC address
src-port (integer: 0..65535-integer: 0..65535{*}) - source port number or range
tcp-mss (integer: 0..65535) - matches TCP MSS value of an IP packet
time (time-time,sat | fri | thu | wed | tue | mon | sun{+}) - 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{0,1}; default: 0.0.0.0) - address or address range to replace original address of an IP packet with
to-ports (integer: 0..65535-integer: 0..65535{0,1}) - port or port range to replace original port of an IP packet with
tos (max-reliability | max-throughput | min-cost | min-delay | normal) - specifies a match to the value of Type of Service (ToS) field of IP header
max-reliability - maximize reliability (ToS=4)
max-throughput - maximize throughput (ToS=8)
min-cost - minimize monetary cost (ToS=2)
min-delay - minimize delay (ToS=16)
normal - normal service (ToS=0)
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