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Closed 7 years ago.
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In ping , is it the replay echo and request echo take the same routes ?
and why ?
in other terms do reply messages take the reverse path of the request messages ?
A Ping is in fact an ICMP packet either indicating a request or reply. I would say that the answer to your questions in general is No since there's no guaranty that the path from your host to the destination is the same as the path from the destination to your host. Normally, this depends on the current status of the Network, the routing protocol used by your ISP and many other parameters.
Any way the ping is intended to calculate the round-trip delay (RTT) between your host and the destination. Thus, if the packets are traversing the same path or not should be transparent to any application you are using.
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Closed 5 years ago.
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Is there any Linux command/Bash script for wireless clients to know the number of clients connected to each WiFi SSID ? How can I do this in bash ?
I am not sure what you want to achieve, so I will give you several answers to point in different directions.
To get all SSIDs (including all public information) you can use the following ...
$ su
# iwlist scan
I hope this is what you looking for.
If not, then you maybe want to know how many active connections one service is carring. This is by far more complicated. To check for active connections you will need a port sniffler like tcpdump and huge knowlegde.
A more common way would be to access the log files or the protocol of the server, but I think you had not asked if you have the rights to do so.
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Closed 4 years ago.
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I have a squid proxy server with 10 public IP addresses, I am using it precisely for the purpose of outgoing address. I want this multiple IP addresses to be randomly elected and changed every 2 minutes when the requests go out of the server. is that possible? how to do it in a server side, and what exactly we need to do in the client side?
Regards
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Closed 7 years ago.
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Our clients occasionally fail to connect to our web server (CentOS 6.5, Kernel 2.6.32-504.1.3.el6.x86_64, Apache 2.4.x). The captured packets show that the server set the window size to zero during the three way handshake and then reset the connection (as shown in the screenshot below). I would love to know
1) What condition(s) would cause such an issue?
2) Is there a way to proactively monitor it? If the reason is that the kernel run out of some kind of memory, is there a way to monitor its usage & upper bound?
3) Is there any tuning that can be done?
Many thanks in advance.
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Closed 8 years ago.
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My computer has only one network card. I have a program listening on one port. I intend to send one packet on the same machine, my program can receive the packet. I can't capture the packet by tcpdump on the machine which my program is running on.
If I send packet from another machine, tcpdump can capture the packet.
If i understand you correctly, you send the packet from a machine to itself.
If so, you need tcpdump on the loopback interface.
e.g.
tcpdump -i lo
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Closed 9 years ago.
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I use an Linux Server for nat device.
Currently it looks like [PC1,2,3]--[Linux]--[Internet]
There is no issue at all , but I'm curious about , when I open a service (ex: FTP WWW ) on my PC1 , did my [Linux] also opened a port service on it ?
I did trace code for the
CONFIG_NF_CONNTRACK_FTP
CONFIG_NF_NAT_FTP
but I cant find related code about port open.
Thanks for your read.
There are various techniques used the make a router/firewall automatically forward ports to its clients. For example there are some protocols like: IGD, NAT-PMP et similia.
But those protocol need to be implemented both on router and on client. So automatic port-mapping won't work out of the box in many cases.
The lines in kernel config you are referring to CONFIG_NF_CONNTRACK_FTP CONFIG_NF_NAT_FTP are used for another reason: due to the fact that FTP protocol use two different tcp streams for comunication (one of which does not have to be "listened" by the server) your firewall needs extra "effort" to track the connection and act accordingly.