Hot answers tagged internet
12
IP Network Troubleshooting
There are a few standard things you can look for when you are experiencing network connectivity issues. These are listed here from a top-down, or least fundamental to most fundamental issues.
All the example ip commands shown here use a Linux-specific tool called iproute2. Many of the tasks can likely be done with ifconfig and ...
10
check iftop and nload
iftop does for network usage what top(1) does for CPU usage. It listens to network traffic on a named interface and displays a table of current bandwidth usage by pairs of hosts. Handy for answering the question "why is our ADSL link so slow?".
nload is a console application which monitors network traffic and bandwidth usage ...
9
You have the symptoms of an MTU problem: some TCP connections freeze, more or less reproducibly for a given command or URL but with no easily discernible overall pattern. A telltale symptom is that interactive ssh sessions work well but file transfers almost always fail. Furthermore pppoe is the number one bringer of MTU problem for home users. So I ...
6
Maybe setup smokeping on the Linux side, and point it at your AP?
Smokeping will periodically (configurable) send -20 pings at the same time, and then graph how how many returned and the range of times that they returned in. If you have a lot of dropped packets, or the really wide range, then you should be concerned.
If you want to run smokeping you ...
6
Deleting the default route should do this. You can show the routing table with /sbin/route, and delete the default with:
sudo /sbin/route del default
That'll leave your system connected to the local net, but with no idea where to send packets destined for beyond. This probably simulates the "no external access" situation very accurately.
You can put it ...
6
I'd highly recommend you use RSA keys rather than passwords for remote SSH logons.
Second, you'll want to install Fail2Ban or something similar to discourage brute force breakin attempts (although again, disabling password authentication in favor of RSA public/private key authentication for SSH access would make this a mostly moot point)
Third, it's ...
6
You could use Linux containers to create an environment with no network interfaces. For example, if I create a configuration file like this:
# lxc.network.type = empty
And then start a shell like this:
# lxc-execute --name bash -f /tmp/lxc.conf /bin/bash
I will find that within this shell there are no network devices available other than lo:
# ...
4
They're in the $http_proxy, $https_proxy and $ftp_proxy environment variables. Also, $no_proxy contains a comma-separated list of host patterns for which no proxy is used. For example:
http_proxy=http://proxy.example.com:3128/
no_proxy=localhost,127.0.0.1,*.example.com
4
You wrote
So, how do I simulate "no external
access" in my development machine?
How do I "deactivate" my ethernet
interface and reactivate later with no
hassle?
Are these two questions or one question? I'm not sure what you mean by simulate "no external access". However, to deactivate the ethernet interface you could simply do
#ifdown eth0
...
4
Make sure you keep your SSH server up-to-date. OpenSSH has a good security record, but you don't want to.
Consider carefully whether you need to allow password authentication. Normally you should be logging in only from trusted computers (don't type a password on a computer that may be running a key logger), and these trusted computers are generally under ...
4
So, basically your Linux box acts as a firewall?
First, enable IP forwarding.
echo 1 > /proc/sys/net/ipv4/ip_forward
echo 1 > /proc/sys/net/ipv4/conf/all/forwarding
Then, add some forwarding rules:
iptables -A FORWARD -i eth0 -j ACCEPT
iptables -A FORWARD -m state --state ESTABLISHED,RELATED -j ACCEPT
Secure the FORWARD chain:
iptables -P ...
4
One of the easier ways would be to run the WINE program as a different user and set up netfilter to drop packets from that user.
Eg, where "wineusername" is your Wine user and em1 is your network interface:
iptables -A OUTPUT -o em1 -m owner --uid-owner wineusername -j DROP
iptables -A FORWARD -o em1 -m owner --uid-owner wineusername -j DROP
iptables -A ...
3
There are three parts in your question, in fact:
Decide on a blocking strategy at the network level: what connections are allowed?
Implement that blocking strategy.
… in a way that only affects certain users.
Blocking websites is not easy. In fact, I would say that it's impossible to completely block a website without completely blocking network access. ...
3
Is there a chance that your IP is duplicated on the network?
Given that you have done all of this testing the next step would be to use an intermediate hop in between and go to the website from your computer.
Use a free proxy online. There are several available. I have seen this issue before and it turned out that the IP was being blacklisted blackholed by ...
3
You could try flushing out your DNS. You could set your DNS to 8.8.8.8 (google public DNS server). You might also clear out your arp cache.
for arptable in `arp | grep "eth1" | cut -d " " -f1`; do arp -d $arptable; done
3
I ran into this problem as well, although not as frequently as every day.
Someone else who had a similar problem was told to disable IPv6 and it apparently worked: http://ubuntuforums.org/showthread.php?t=1528202
I'm trying to do that as well using more updated instructions from: http://www.noobslab.com/2012/05/disable-ipv6-if-your-internet-is.html
Let me ...
3
From your output, you are not able to reach the destination. The * denotes a timeout.
traceroute command shows the path to your destination. packets send to will pass through the routers and you receive a response obeying the time to live (TTL) value for each packets. the * denotes a timeout as a response from the intermediate routers that says the packet ...
3
The thing to remember is that getting used to something new, like a new operating system, is stressful.
Unfortunately, I haven't got freeBSD in front of me at the moment, but assuming that there is a driver for your ethernet card (which there is in all likelihood), the first thing you should try at a command prompt is,
ifconfig -a
This will show you what ...
3
Yes, simply run the following command :
iftop
iftop does for network usage what top(1) does for CPU usage
See http://www.ex-parrot.com/~pdw/iftop/
3
The wifi being "connected" only gives you the physical layer.
Are your IP settings plausable? Did you set static IP because DHCP didn't work at home?
ifconfig wlan0 (or name of wifi interface)
Check routing
route -n
Do you have a default gateway? If not, set the correct one
route add default gw <ip of gateway>
Can you ping an internal address ...
2
echo 1 > /proc/sys/net/ipv4/ip_forward
or edit /etc/sysctl.conf and set 1 to the net.ipv4.ip_forward (It should be net.ipv4.ip_forward=1). This will make that change persistant after a reboot.
iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
(or you can save it in rc.local file)
eth0 - replace with your Dell Wifi port
connect the two ...
2
Use tcpdump to capture packets that are leaving your local LAN subnet. Then use tools like Wireshark or tshark to do some analysis on how much loss you're experiencing, as well as what the variance in round trip time is, and how TCP is behaving. (Windowing, retransmits, etc).
The reason I suggest this rather than running some sort of ping/traceroute based ...
2
It appears that the core problem is something to do with SSL. All of your problem URLs are https://.... ones.
I don't see why a change to PPPoE affects this, but perhaps your ISP changed more than one thing at once, and you're blaming the wrong change.
I would try adding a hardware router, one specifically recommended by model number by your ISP. Not ...
2
You could run your code in a virtual machine (User Mode Linux, VServer, OpenVZ, VirtualBox, VMWare, KVM, …) that you provide with only a host-only network interface (i.e. no routing from the VM to anywhere but the host machine).
If you run the application as a dedicated user appuser, you can restrict that user's network access. Make sure you have iptables ...
2
Ethernet bonding requires that both ends on the link support bonded interfaces and must be part of the same network space. Usually bonding is only done as far as a computer to the nearest switch. You cannot bond two different routes to the internet. Your 3G card is going to have an address from your cellular provider, and your wifi from some other ISP. You ...
2
The short answer is - no you will need to try the FTP connection via libcurl and see if the authentication succeeds.
The username/password only exist on the remote server, and you don't know if they are being changed or altered at any stage (for legitimate reasons). Hence, your code will have to take credentials from the user, and basically try an FTP ...
2
Some ideas:
You could use the ping plug-in for collectd to monitor ping time from your ubuntu gateway to some selected internet hosts.
If your router supports SNMP, You could use mrtg to monitor traffic on the router interfaces.
You could install smtpd on your ubuntu gateway and use mrtg to monitor the gateway interfaces.
Last, but not least, you could ...
2
This is definitely feasible. Many of us were running mixed, load-balanced broadband configs for corporate years ago and they worked really well. Many probably still do!
You can do it in a number of ways, including using iptables rules and/or iproute2 (ip(8) command) to setup policy routing.
The load balancing is not done at the packet level, but at the ...
2
If you install one of the parental controls apps e.g. Nanny you can restrict the amount of time a user has access to the Internet to zero/never.
There are other parental controls apps, don't have one in particular to recommend but this should give you the level of control you want, with the simplicity of a GUI app.
2
You can share the internet by configuring the Cent OS server as a NAT machine and giving private ip addresses to the LAN machines. As in your case, the USB wireless interface is ppp0 and the LAN interface is eth0 on the Cent OS server.
Step-1: Providing private ip addresses to LAN interface on Cent OS and to the other machines in the LAN.
You can give any ...
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