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4

OK, i believe i understand the question now. host1 Let us assume that you have host1 to which you connect with ssh via putty, on this host you shall install screen or tmux (from the package manager, they shall be there). I suggest screen since it is a little easier for a beginner. Also, you need to be able to login to host2 from host1 therefore you need ...


1

for i in `cat servers.txt` ; do ping -c1 $i 2>&1 | tee >> ping-output.txt; done This executes a ping for each line in the file (using i as the variable that stores the value and referencing the variable with $i) and redirects all output into the [output] file. The 2>&1 part captures the stdout (ping results) and the stderr (no ping because ...


3

@Julie Pelletier's answer is 100% correct, but probably not very understandable to you. First, as mentioned several times in the comments, the mark is not put into the ethernet packet on the wire. So if you ping server B from server A, server B will not ever be able to detect the mark. If you want to do anything, you'll have to use server A alone. So, ...


6

That mark is internal and not included anywhere in the packet or any of its headers. That means it gets lost when doing the actual outbound connection, and wouldn't be visible in the INPUT table of the target server, but you would see it in the OUTPUT table of the initiating machine. The point of supporting a mark in ping is to allow outbound routing ...


2

You're missing pass proto icmp. It's usually a reasonable measure to have as your first pass rule: pass quick proto icmp Otherwise you're implicitly blocking that traffic. ICMP is its own protocol, remember, and not covered by TCP or UDP. See the OpenBSD page on PF.


0

Use ssh -v on originating system, check /var/log/* on target. Try timing access by IP address as well as by hostname.


0

Why the preload limit is limited to 3 for normal users ? So that normal users can't take down the network with ping. Nowadays it's harder to take the network down with pings but before with slower networks you had to limit users on how they could use pings.


1

Using -l makes the ping utility "shotgun" all the tested packets out at once, rather than at one second intervals. This can be useful if you're testing things more sensitive to bursts of data than basic connectivity.


3

Basically, the raw socket will capture all ICMP packets. The internal number you quote is exactly to identify packets from the current process. There's no port number in ICMP to allow per-socket demultiplexing by the protocol stack. To answer your comment, if the packet has been received, it hasn't been lost, has it? All sockets set up like ping does get ...


1

Finally I have figured out what the problem is! It is most likely because of an IP Conflict ._. Sorry to bother you guys. After I have switched from fix IP to DHCP, no packets loss in ping anymore. Thanks guys. Lesson learned.


15

Short answer: You can't do with a normal user. Long answer: To be able to mark packets, you need to be a root user, or at least a user with the SO_MARK capability(needs to be set as root): SO_MARK at socket(7): SO_MARK (since Linux 2.6.25) Set the mark for each packet sent through this socket (similar to the netfilter MARK target ...


1

The only possible difference would be DNS related or if your computer is awfully slow. This gives an imprecise reading which is why it is not the default behavior anymore.


1

These details are implementation specific. The packet size is exactly as you would expect. Using a smaller buffer size could in theory cause fragmentation of the packets but that doesn't happen on any system I've tried it on. The result you obtain showing only 72 bytes received is because your VPS has severe restrictions which limit the packet size to 64 ...


5

The -T option asks nodes (each hop) to insert a timestamp in the IP packets upon receiving a ping. It works by using the TS option of IP packets, specified by RFC791. ping -T requires one argument of tsonly, tsandaddr or tsprespec. tsonly returns only the timestamp. tsandaddr returns the timstamp and the address the packet was sent from. From the man ...


1

From the ping man -T timestamp option Set special IP timestamp options. timestamp option may be either tsonly (only timestamps), tsandaddr (timestamps and addresses) or tsprespec host1 [host2 [host3 [host4]]] (timestamp prespecified hops) The IP timestamp option is an IP packet option field used to record timestamps (in Universal Time) of every device ...



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