03-21-2012
Each end of the connection has its own port. You're connecting to port 80 on google, but your own port is going to be a random number >32768. Let's call it 40,000.
So your PC transmits a connection request to google.com on port 80, from 192.168.134.100 port 40,000. It travels through your router, which marks down "forward traffic to port 40,000 to 192.168.134.100". It will continue forwarding this connection until it's explicitly broken, or the connection lies idle a few minutes (a highly annoying fact sometimes when you don't want idle connections to break!) This process is part of Network Address Translation(NAT).
These local port numbers are randomly picked, allowing many connections to coexist alongside each other without their ports overlapping.
These 2 Users Gave Thanks to Corona688 For This Post:
9 More Discussions You Might Find Interesting
1. IP Networking
i have one private network with one ip address, and i have a seperate network on a seperate ip address.
now, each network is behind a firewall/router. now what i want to do is be able to access one server on the second network from a computer on the first., but with the private ip address, (this... (2 Replies)
Discussion started by: norsk hedensk
2 Replies
2. IP Networking
Hi all,
Currently we are in the progress of setting up a private network on all of our Sun Solaris servers. Purpose is to move all backup tasks to the private, hence reduce load on public network.
Some of our servers only consists of 1 network card but with several ports. Shall we purchase... (10 Replies)
Discussion started by: *Jess*
10 Replies
3. HP-UX
Hi there,
i have a Problem..
i have a Visualize J5600 and HP-UX installed on it..
So i want to go Online with the machine and surf in the Internet..
But i dont know what i do wrong... :(
I installed HP-UX and run SAM
I am from Germany and my provider is T-Online.. my Router has the... (3 Replies)
Discussion started by: deepimpact26
3 Replies
4. IP Networking
Hello all,
I have installed ubuntu hardy and for some testing I have configured sendmail on it.
I have a router facing the internet and I am having hard time configuring the router to allow traffic on port 25 to my server. I have a BCM96338 ADSL Router. I have set iptable rules to allow the... (0 Replies)
Discussion started by: h3llh0l3
0 Replies
5. Shell Programming and Scripting
Hi everybody. I have the next scenary:
eth0: WAN
eth1: DMZ
eth2: LAN
I need to block all incoming trafic from the internet through my network LAN using iptables. I have squid but i need to do this using ipatbles.
I have been listening about iptables -A FORDAWARD but I am stuck right... (0 Replies)
Discussion started by: edeamat
0 Replies
6. Cybersecurity
Hi all,
How can I monitor packet traffic on my wireless router?
Some info
- my wireless router is netgear wgr614
- everyone can connect it i.e. no password required
- I would like to see where they connect, how they are using the internet connection
I installed wireshark and captured... (3 Replies)
Discussion started by: SaTYR
3 Replies
7. Windows & DOS: Issues & Discussions
Hello,
I have a desktop which has two network cards installed on it and I connected these two card through a hub.
On the desktop in have installed a Windows Vista Home Edition SO and a Windowx XP SO in a virtual way. I also had intalled a Virtual BOX software and Windows XP run through it.
By... (1 Reply)
Discussion started by: zendcool
1 Replies
8. IP Networking
So I want to limit the download and upload speed of a specific ip adress in a local network. To do this I are using a bach script running in a linux OS (Ubuntu 11.04). The issue here is that the upload shaper does not work. I have tried an alternate solution aswell though that does not work as... (0 Replies)
Discussion started by: martio09
0 Replies
9. IP Networking
My son does homework on a school laptop. I was thinking about setting up a gateway on my home network, so that I can monitor web traffic and know if he is doing his homework without standing over his shoulder. Ideally I would like to use the Raspberry Pi Model b that I already have. However, I... (15 Replies)
Discussion started by: gandolf989
15 Replies
LEARN ABOUT FREEBSD
if_gre
GRE(4) BSD Kernel Interfaces Manual GRE(4)
NAME
gre -- encapsulating network device
SYNOPSIS
To compile the driver into the kernel, place the following line in the kernel configuration file:
device gre
Alternatively, to load the driver as a module at boot time, place the following line in loader.conf(5):
if_gre_load="YES"
DESCRIPTION
The gre network interface pseudo device encapsulates datagrams into IP. These encapsulated datagrams are routed to a destination host, where
they are decapsulated and further routed to their final destination. The ``tunnel'' appears to the inner datagrams as one hop.
gre interfaces are dynamically created and destroyed with the ifconfig(8) create and destroy subcommands.
This driver corresponds to RFC 2784. Encapsulated datagrams are prepended an outer datagram and a GRE header. The GRE header specifies the
type of the encapsulated datagram and thus allows for tunneling other protocols than IP. GRE mode is also the default tunnel mode on Cisco
routers. gre also supports Cisco WCCP protocol, both version 1 and version 2.
The gre interfaces support a number of additional parameters to the ifconfig(8):
grekey Set the GRE key used for outgoing packets. A value of 0 disables the key option.
enable_csum Enables checksum calculation for outgoing packets.
enable_seq Enables use of sequence number field in the GRE header for outgoing packets.
EXAMPLES
192.168.1.* --- Router A -------tunnel-------- Router B --- 192.168.2.*
/
/
+------ the Internet ------+
Assuming router A has the (external) IP address A and the internal address 192.168.1.1, while router B has external address B and internal
address 192.168.2.1, the following commands will configure the tunnel:
On router A:
ifconfig greN create
ifconfig greN inet 192.168.1.1 192.168.2.1
ifconfig greN inet tunnel A B
route add -net 192.168.2 -netmask 255.255.255.0 192.168.2.1
On router B:
ifconfig greN create
ifconfig greN inet 192.168.2.1 192.168.1.1
ifconfig greN inet tunnel B A
route add -net 192.168.1 -netmask 255.255.255.0 192.168.1.1
NOTES
The MTU of gre interfaces is set to 1476 by default, to match the value used by Cisco routers. This may not be an optimal value, depending
on the link between the two tunnel endpoints. It can be adjusted via ifconfig(8).
For correct operation, the gre device needs a route to the decapsulating host that does not run over the tunnel, as this would be a loop.
The kernel must be set to forward datagrams by setting the net.inet.ip.forwarding sysctl(8) variable to non-zero.
SEE ALSO
gif(4), inet(4), ip(4), me(4), netintro(4), protocols(5), ifconfig(8), sysctl(8)
A description of GRE encapsulation can be found in RFC 2784 and RFC 2890.
AUTHORS
Andrey V. Elsukov <ae@FreeBSD.org>
Heiko W.Rupp <hwr@pilhuhn.de>
BUGS
The current implementation uses the key only for outgoing packets. Incoming packets with a different key or without a key will be treated as
if they would belong to this interface.
The sequence number field also used only for outgoing packets.
BSD
November 7, 2014 BSD