Below is the setup I have,
MC#1 (eth0) <-> MC #2 (eth1)
With this setup, I have created a TAP interface in MC#1 and tried to ping the IP assigned to TAP interface from MC#2. When I checked the tcpdump the destination mac address is shown as the eth0 interface of MC#1 and not the MAC of the TAP interface. Also when I checked the ARP entries in the MC#2, I am able to see the MAC address of eth0 (MC#1) against the TAP interface IP.
Please explain why this happens and can we make some changes in the kernel so that the MAC address of the TAP interface to be used.
Thanks
I learned (using openvpn server) that when you ping from server (network that you want to connect to) side from host to local computer's ip, in short ARP entry is updated on local machine and it is reachable (after several tries). pinging from local computer to others not always help and might take some time. It is probably some bug with updating windows APR tables in TAP interface.
Related
My internet is only working for heavily cached sites. Reddit, Gmail, Facebook, etc. The odd thing is, sites like Reddit make queries to non-reddit sites to import the images and they pop up fine when viewing from there, but when I get sent to out.reddit.com and then if I go elsewhere to other non-heavily cached sites, I get timed out connection error.
I can't even visit SpeedTest.net because it times out. I also can't even post a question on StackExchange because of it. What could possibly be going on and how to I debug?
EDIT: I had an inclination that it had to do with Docker. I removed all traces using a powershell script and through remove programs and still didn't work.
user3654055 are friends IRL and we debugged this in person.
It's always best to start from layer 1 and work our way up.
user3654055's computer could connect to wireless networks. This tells us layers 1 and 2 are working
.
user3654055's computer received a DHCP lease. Further testing of layer 3 showed inconsistent results with pinging local IP addresses.
I ran route print to print all routes. This produced a huge amount of output.
Normal output for a Windows computer connected to a flat LAN should produce perhaps 3 routes.
user3654055 had recently installed Docker and attempted to set up a private
internal network for the containers on their PC.
user3654055 had created two virtual networks (one internal vEthernet switch, one external vEthernet switch), a NAT interface, and bridged the wireless adapter to one of those interfaces and had not set up routing correctly for any traffic.
This produced the above scenario where certain traffic was routed correctly or hit the cache and the page would load, but most traffic was routed incorrectly and resulted in a timeout.
Disabling all the vEthernet switches and the NAT interface and removing the wireless adapter from the bridge let the user use their wireless card again.
The above configuration could work if the user set up routing correctly by hand, but we can save that for a later date.
Sounds like a DNS issue...do you know what you are using as a DNS address? You could try using Google's which is 8.8.8.8 for primary and 8.8.4.4 for secondary. Failing that does it get better following a router reboot?
To debug your internet connection, I would at first check what happens with tracert.
Traceroute command shows you the path taken by your packets and its latency from hop to hop.
From console (linux) or from cmd (windows)
tracert stackoverflow.com
this shows you where you are lagging, the first entry may be your router IP. If the first entry appears with high latency try to reboot your router.
Checking for DNS Issues
Try to use nslookup. This is what you should get:
nslookup stackoverflow.com
Server: UnKnown
Address: 192.168.1.1
Risposta da un server non autorevole: //italian comment
Nome: stackoverflow.com.home
Address: 54.72.52.58
if this fails or replies with high latency try to change your DNS to Google DNS.
Primary DNS: 8.8.8.8
Secondary DNS: 8.8.4.4
There is a lot of other answers related to this issue, however I believe this is specific.
I am using Delphi XE2 and Indy 10.5.8 and TIdUDPServer
In my local development network I have everything on the same network ip subrange and all connected to the very same Access Point (LinkSys)
I have Androids sendind UDP Broadcast to 255.255.255.255 to request the server ip address that is written in Delphi listening using TIdUDPServer on the port 44444.
The requests get there fine and I can answer back no problem. Works exactly as expected.
However I have noted that in some networks it does not work! It is always simple networks based on an access point, I am not sure but seems that where the problem happens the server PC is connect to the LAN port while the devices are using the wifi, all in the same access point.
Could be the case that the access points do not broadcast the UDP packet by the both LAN and wifi? I know that this kind of broadcast is very limited, but I have not found any information that tell me that in the same access point there is limitations like that.
Is there are ways to test, or workaround?
This solution needs to be strong enough to deal with the many AP out there.
EDIT: For those that want to get the source code for retrieving more information from the network including the broadcast ip as mentioned on the answer below follow this solution, it is all there.
http://www.code10.info/index.php?option=com_content&view=article&id=54:articleretrieve-network-adapter-information&catid=47:cat_coding_algorithms_network&Itemid=78
255.255.255.255 is not the best option for sending UDP broadcasts, and some routers/firewalls do block it unless configured otherwise. The better option is to use the NIC's actual subnet broadcast IP instead. For example, if a UDP socket is bound to local IP 192.168.0.1 with a subnet mask of 255.255.255.0, then the broadcast IP for that subnet is 192.168.0.255.
Most platforms have OS-specific APIs for retrieving a NIC's actual broadcast IP, such as getifaddrs() on POSIX systems, or at least for retrieving the NIC's subnet mask, such as GetAdaptersInfo() and GetAdaptersAddresses() on Windows, so you can calculate the broadcast IP manually.
Retrieving the local broadcast IP(s) may be added to Indy in a future version.
I would like to do a scan in a LAN network to find devices linked.
I'm developping an app in IOS for IPAD
How do I do???
Because those are mobile devices I will assume you want to find devices on a wireless network. Theoretically, since wifi uses shared medium for communication, you can passively listen for traffic flowing through the network and collect data about client without sending any packets. This is something that is commonly referred to as a promiscuous mode. In practice there is 99% chance that the network adapter driver will allow you only to get traffic destined for your MAC address. In that case you will need to resort to actively scanning the network subnet which is not 100% accurate and depending on how the network is implemented can be considered as a possible attack.
The simple way of scanning is sending ICMP requests (ping) to every IP address in the subnet and collecting data from those who send back the echo reply. This is not reliable because some hosts won't respond to ICMP echo request even if they are active. First thing you need is to find out your own IP address and the subnet mask, and calculate the range of possible addresses in your subnet. The range is obtained by using logical AND operator where operands are binary values of your IP address and subnet mask. This is an example from the program that calculates this for typical 192.168.1.1 subnet with 255.255.255.0 subnet mask (192.168.1.1/24 in CIDR notation):
Address: 192.168.1.1 11000000.10101000.00000001 .00000001
Netmask: 255.255.255.0 = 24 11111111.11111111.11111111 .00000000
Wildcard: 0.0.0.255 00000000.00000000.00000000 .11111111
Network: 192.168.1.0/24 11000000.10101000.00000001 .00000000
Broadcast: 192.168.1.255 11000000.10101000.00000001 .11111111
HostMin: 192.168.1.1 11000000.10101000.00000001 .00000001
HostMax: 192.168.1.254 11000000.10101000.00000001 .11111110
Then you would iterate through the range and ping every address. Another thing you can consider is listening for broadcast traffic such as ARP and collecting some of the information that way. I don't know what are you trying to make but you can't get many useful information this way, except for vendor of a host's network adapter.
Check my LAN Scan on Github. It does exactly what you want.
I recently used MMLANScan that was pretty good. It discovers IP, Hostname and MAC Address.
Bonjour have been around since 2002, have a look at it!
I mean, just look at their current tagline:
Bonjour, also known as zero-configuration networking, enables automatic discovery of devices and services on a local network using industry standard IP protocols. Bonjour makes it easy to discover, publish, and resolve network services with a sophisticated, yet easy-to-use, programming interface that is accessible from Cocoa, Ruby, Python, and other languages.
Writing WinXPe NDIS 5.1 device driver. Started with Intel E100 driver source from DDK and adapting to Altera triple-speed ethernet core. Receive packet through scatter gather DMA working well, can see good data. Transmit packet through separate scatter gather DMA claims to be working well. Problem is that ipconfig shows IPv6 only IP address for the NIC. Control Panel, Network Configuration, Internet Protocol, has set static IPv4 IP address and no DHCP. But ipconfig doesn't see it. Can't find any OIDs which appear to tell WinXPe anything about IPv6 versus IPv4. Control Panel, Network Configuration correctly updates itself for ethernet connect and disconnect, but nothing seems to please ipconfig. Where is ipconfig getting its IPv6 information, and how can the driver affect it? Thanks.
The problem was an incomplete implementation of OID_GEN_CURRENT_PACKET_FILTER which inhibited the higher level driver from passing IPv4 packets to/from the driver. Although none of the flag bits in OID_GEN_CURRENT_PACKET_FILTER appears relevant to IPv4 [or IPv6], it mattered. Took a call to Microsoft on my MSDN account to resolve this.
I have a local network at my home and have a system addressed at 192.168.2.2 in the local network. I want to access this local system from outside(of course I am aware of the Global IP) using both ssh and using URL. How can I do it? (Apache is installed in my system.)
There are few posiblities.
First if you are targeting specific computer outside your home network and this computer has known IP you can initiate connection from your home PC to this computer using some program like Putty.
If you want to access your computer from anywhere at any time, than some kind of service should be used, google for "dynamic DNS free". Depending on your Internet connection you will make changes on your PC on your Router.
To acces SSH from outside you need to portforward that port.
See http://en.wikipedia.org/wiki/Port_forwarding for more information