IP NAT

mahesh_kv3 · ‎08-12-2007

Cud u please explain me wen a packet from public came ...how it will work acccording to the NAT translations given below in ma router

Pro Inside global Inside local Outside local Outside global

tcp 218.248.255.100:61764 172.30.7.3:61764 192.6.165.75:21 192.6.165.75:21

--- 218.248.255.96 172.30.7.154 --- ---

--- 218.248.255.97 172.30.7.15 --- ---

--- 218.248.255.98 172.30.7.184 --- ---

--- 218.248.255.99 172.30.7.11 --- ---

--- 218.248.255.100 172.30.7.3 --- ---

--- 218.248.255.101 172.30.7.183 --- ---

--- 218.248.255.102 172.30.7.1 --- ---

--- 218.248.255.105 172.30.7.77 --- ---

--- 218.248.255.106 172.30.7.50 --- ---

--- 218.248.255.107 172.30.7.111 --- ---

--- 218.248.255.108 172.30.7.200 --- ---

--- 218.248.255.109 172.30.7.185 --- ---

--- 218.248.255.111 172.30.7.78 --- ---

--- 218.248.255.131 172.30.7.206 --- ---

--- 218.248.255.132 172.30.7.187 --- ---

--- 218.248.255.134 172.30.7.55 --- ---

tcp 218.248.255.100:522 172.30.7.3:522 172.30.80.21:514 172.30.80.21:514

tcp 218.248.255.100:521 172.30.7.3:521 172.30.80.24:514 172.30.80.24:514

tcp 218.248.255.100:570 172.30.7.3:570 172.30.80.27:514 172.30.80.27:514

tcp 218.248.255.100:581 172.30.7.3:581 172.30.80.27:514 172.30.80.27:514

mohammedmahmoud · ‎08-12-2007

Hi,

The entries having the "---" are static entries, the first ip is the Inside local and the second is the Inside global, please check the following document:

Local and Global Definitions:

http://www.cisco.com/warp/public/556/8.html

For the above entries any packets received on the inside interface are NATed to the inside global ip address and sent out the outside interface and vice versa, and this type of NATing is permanent and the traffic can be initiated either from inside or from outside..

The other entries are dynamic entries, 514 is syslog and 21 is FTP traffic, this type of NATing can only be initiated from inside to outside and the NATing is afterwards used in both directions (same flow only).

Always remember:

In static NAT, a translation is statically configured and is placed in the translation table without the need for any traffic, and they remain in the translation table until you delete the static NAT command(s). While with dynamic NAT, the translation table in the router is initially empty and gets populated once traffic that needs to be translated passes through the router, also dynamic translations have a timeout period after which they are purged from the translation table.

HTH,

Mohammed Mahmoud.