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The show nat commands provide information on the configured and operating state of a router's NAT (Network Address Translation) variables.
show nat {config | map | sessions | statistics | address_db}
config | This command shows the current configuration of the NAT variables, including the NAT mapping translation pairs and the NAT map database. |
map | This command shows the one-to-one address translation pairs currently entered in the router, or displays a message that no one-to-one address pairs are presently entered in the NAT map database. |
sessions | This command displays the translation sessions currently active in the router's NAT software. |
statistics | This command displays the total number of sessions the router has created since it was lasted booted, how many are currently active and the status of those sessions which are no longer active. |
address_db | This command displays all of the IP addresses being used by the router for Network Address Translation. |
The following sections describe the display contents for each command.
The show nat map display is read as the internal address (10.5.3.20) which is translated to/from the external address (198.41.9.194). Packets addressed to 198.41.9.194 from the Internet will be accepted by the router, translated to the destination address 10.5.3.20 and sent to the internal NAT network by the router.
The show nat sessions display includes:
Active Map | This is the IP address:port internal-to-external address translation. If the translation is not to or from a specific port, then the port value will be 0. |
Remote | This is the location on the external Internet communicating with the workstation or router in the internal NAT network. |
Proto | This is the protocol the session is translating. Current values for this column are ICMP, UDP, and TCP, or the actual number of the other IP protocols. |
Hashes | This is the information used by the software to store and locate the translation sessions in the NAT internal database. |
Time Since:Created | This is the time, in seconds, since the session was created. |
Time Since:Last Activity | This is the time, in seconds, since the session was last used to translate an IP packet. |
The show nat statistics display includes:
Total Sessions | This is the total number of NAT sessions created to translate IP packets since the router was last booted. | ||
Filtered | Filtered currently has no values defined. | ||
Currently Active | This is the number of sessions presently being used by the router to translate packets. | ||
Properly Removed | This is the number of sessions removed from the NAT session database as a result of FIN and ACK packets being exchanged between the workstation/router on the NAT network and the workstation/router on the Internet. The IP session is terminated and the NAT session doing the address translation is likewise removed from the NAT hash database.
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Sessions Timed Out | This is the number of NAT sessions removed from the NAT hash database as a result of a time limit being exceeded. There are three types of time outs:
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Sessions Reset | This is the tally of the NAT session for which an RST packet was sent. Invalid Cache, No Resources, and Stale ACK currently have no values defined. |
The show nat address_db display includes:
Address Tree Level | This is the search depth of the IP addresses in the database. Each plus sign (+) indicates a deeper level within the address tree. |
IP Address | This is either an internal or external IP address which is being used by the router for NAT. The Flags indicate which type of address it is. |
IP Mask | This is the hexadecimal representation of the mask associated with each address. |
Flags | This shows all flags which apply to each IP address in the NAT Address Database. The flags are defined briefly in the "Flag Legend" at the end of the display. |
The following sections show an example for each command.
The following is the output from the show nat config command:
NAT functionality enabled (On/Off): On
NAT Response to external ICMPs (On/Off): On
Communicate w/ Router through IP Ports (On/Off): On
Configured Ports: Ether0
UDP timeout period (sec.): 300
TCP timeout period (sec.): 86400
TCP SYN timeout period (sec.): 180
TCP FIN timeout period (sec.): 180
Entered Internal range(s):
10.5.3.0/27
Entered External range(s):
198.41.9.219
198.41.9.195
198.41.9.194
Entered Pass Thru range(s):
198.41.9.{205-210}
[ NAT Map Database ]
Total Number of Entries in NAT Map Database: 2
--------------------------------------------------
Internal External
LineNo. <IPaddress[/Mask or :Port]> -> <IPaddress[/Mask or :Port]>
1 <10.5.3.11:80> -> <198.41.9.195:80>
2 <10.5.3.20/32> -> <198.41.9.194/32>
The following is the output from the show nat map command:
Nat_2220> show nat map
[ NAT Map Database ]
Total Number of Entries in NAT Map Database: 1
--------------------------------------------------
Internal External
LineNo. <IPaddress[/Mask or:Port]> -> <IPaddress[/Mask or:Port]>
1 <10.5.3.20/32> -> <198.41.9.194/32>
The following is the output from the show nat sessions command:
Active Map Remote Proto Hashes
------------------------------------ -------------------- ------ --------
Time Since: Created Last Activity
----------------- ----------------
10.5.3.20:0 ->198.41.9.194:0 198.41.9.200:0 ICMP 221/907
124.33 114.33
10.5.3.20:0 ->198.41.9.194:0 198.41.9.215:0 ICMP 236/922
105.00 104.00
10.5.3.10:29841 ->198.41.9.219:29841 198.41.9.30:53 UDP 255/976
33.93 33.50
10.5.3.10:1899 ->198.41.9.219:1899 198.41.9.12:80 TCP 983/680
25.67 0.16
10.5.3.10:1900 ->198.41.9.219:1900 198.41.9.12:80 TCP 984/681
30.24 15.83
The following is the output from the show nat statistics command:
Total Sessions: 38 Filtered: 0 Currently Active: 0 Properly Removed: 33 Sessions Timed Out: 5 SYN Timeouts: 0 FIN Timeouts: 0 Inactivity: 5 Sessions Reset: 2 Invalid Cache: 0 No Resources: 0 Stale ACK: 0
The following is the output from the show nat address_db command:
Network Address Translation Address Database
Address Tree Level IP Address IP Mask Flags
------------------- ------------------ ---------- ----------
+ 10.5.3.0 0xffffffe0 0x00000001
++ 10.5.3.11 0xffffffff 0x00000019
++ 10.5.3.20 0xffffffff 0x00000009
+ 198.41.9.192 0xffffffe0 0x00001000
++ 198.41.9.194 0xffffffff 0x0000000a
++ 198.41.9.195 0xffffffff 0x0000001a
++ 198.41.9.205 0xffffffff 0x00000004
++ 198.41.9.206 0xffffffff 0x00000004
++ 198.41.9.207 0xffffffff 0x00000004
++ 198.41.9.208 0xffffffff 0x00000004
++ 198.41.9.209 0xffffffff 0x00000004
++ 198.41.9.210 0xffffffff 0x00000004
++ 198.41.9.219 0xffffffff 0x00000002
Flag Legend: INTERNAL: 0x0001, MAPPED: 0x0002, PassThru: 0x0004
1 to 1: 0x0008, PORT in MAP_DB: 0x0010, PLACEHOLDER: 0x1000
| Command | Description |
|---|---|
configure NAT Global | Configures NAT parameters for the device |
edit config NAT Mapping | Creates NAT mappings |
Posted: Wed Sep 27 11:30:20 PDT 2000
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