I'm working on 2.6.15 kernel running on a cisco IPTV. When the box is coming up, the DHCP client hangs up. The reason for this is that the DHCP client does not get fetch the broadcasted DHCP offer message.
When I read /proc/net/dev file, it shows that ethernet device (eth0) has not received any packet. I then ran tcpdump on the box and it also shows that no packet is been received on the ethernet interface.
Then I ran wireshark on the test PC (on which DHCP server is running), it shows that a DHCP offer message is broadcasted by the DHCP server.
This DHCP client and server are working fine with other boxes so there are less chances that these programs have any issues. There must be an issue in the ethernet drivers.
I'm really confused. How should I proceed to this problem. Please help me.
Maybe you can start by checking whether the DHCP client is sending out a discovery.
The DHCP handshake goes like this:
client discovery,
server offer,
client request,
server ack
(Wikipedia has the steps of DHCP)
The next thing you can check any DHCP related settings on the router.
Is the DHCP client on the same subnet/vlan as the server? If not, would the router need a certain configuration to relay to/from the DHCP server subnet/vlan?
Related
I have the following connection in Ubuntu
Linux PC -> Switch (PoE) -> DUT
with the following ip configurations:
Ethernet adaptor Statically assigned
BASE IP (ipv4): 10.0.0.1
subnet : 255.255.255.0
gateway : 10.0.0.0
eth0 network address : 10.0.0.3
This setup enables me to send and receive UDP packets.Works perfectly fine in Ubuntu.
Now in Windows, I have made relevant changes to the python code of the codebase, but the code gets stuck waiting for UDP packets from the Hardware. I have statically assigned the same values as in Ubuntu. I am very new to networking..
(1) I have ensured Firewall is allowing UDP packets
(2) I have made the same IP address,subnet,gateway settings configurations.
Where am I going wrong?
It's impossible to say exactly what goes wrong based on this information.
I'd suggest trying Wireshark from https://www.wireshark.org/.
With that running on your windows PC, you can see if your packets are being sent out or not, and you can also see if the device responds or not. That way you can determine if the problem is in sending or receiving the packets.
Good afternoon need help. There is a router Mikrotik. The Internet and wi-fi started to disappear, but the connection is periodically resumed. The Mac address is specified by my router in an error.
Error in logs : bridge port received packet with own address as source address (ee:ee:8c:0c:ee:fd), probably loop.
You need share a better environment description.
However, assuming you're using wireless interface, you can try proxy ARP on Wireless interface for avoid loops under WiFi bridge.
/interface wireless set arp=proxy-arp
More info here.
Golang application with a client and server.
Server uses net.ListenUDP -- client also uses net.ListenUDP, connects to server and sends a packet with conn.WriteToUDP with the server address.
Server receives the packet with ReadFromUDP and grabs the return address. Using this return address, it then sends a large number of packets back to the client.
When running both client and server on local machine, this works perfectly. Using Wireshark I can inspect the UDP packets and see that they contain the source and destination ports - and in the application I can see that they arrive and my various checksum tests show the data is accurate.
I then moved the server off site to a remote machine. The application stops working. I can successfully send the first message from the client to server - this is received just fine. The server sends the response back 'toward' the client - but the client never receives them.
Using Wireshark, I can see that the packets do arrive back on the local machine with the correct IP address. It appears that my network router has performed NAT on the outgoing packets - and has correctly re-addressed response packets to the internal IP.. BUT there is no port.
So I have UDP packets arriving on the correct machine, but no port - so the client application does not receive them. Application times out on ReadFromUDP.
I don't know if it is relevant, but on local machine, Wireshark labels the packets as BT-uTP Utorrent packets. When they come in from remote server, this is what I see in Wireshark - note the lack of Port.
Any thoughts how I can solve this. I didn't think this was a UDP hole punching problem because although I am establishing a connection across a NAT it is with a server not a peer.
This packet is fragmented, You can see this under Internet Protocol Version 4 > Flags.
If you look at the frame as shown on the bottom of the picture you provided you should see the ports.
net.ListenUDP doesn't appear to support fragmentation at the socket level.
Do you have a PPPoe connection? You may need to reduce your packet size being sent by 8 bytes or change the MTU on the routers external interface of the remote side. You may also need to change the local routers MTU if it's on a PPPoe interface.
I got a bounce message today from a client. In the bounce notice it shows:
The error that the other server returned was:
554-Service unavailable; Client host [mail-io0-f178.google.com] blocked using
554-Barracuda Reputation;
554 http://www.barracudanetworks.com/reputation/?r=1&ip=38.116.199.194
And further down where it shows the original message it says
Received: from Macbook-Pro-Retina.local ([38.116.199.194])
The above is a blocked Russian IP Address. Normally the source of my messages shows:
Received: from Macbook-Pro-Retina.local
(CPE0016cbc430da-CMf0f249004a80.cpe.net.cable.rogers.com. [174.119.**.**])
The 174.119 is my normal external IP address and shows in the source of any message I send. Also I use Google apps for all my mail so its going through their server.
So the question is, is the bounce message a result of an issue on my local machine or does it have to do with the client's server?
38.116.199.194 IP address is part of a 38.0.0.0 - 38.255.255.255 range allocated to Cogent (ARIN WHOIS). A part of this range, 38.116.198.0/23 subnet is operated by MaRS Discovery District.
It appears that your computer was connected to the MaRS Discovery District's network when you sent the email. Maybe you were using their Wifi at the time or maybe some (malicious) software on your machine was routing traffic via that network unbeknownst to you.
I have chosen QuteCom SIP client for windows to chat.I have installed and configured the account with my public server. My SIP server is kamailio.The connection to the server is not established. The application is connecting to the server for a long time.
Any help is appreciated.
If looks like keep connecting, then I guess the SIP messages don't get to the server.
You can install Wireshark to monitor traffic on windows host on port 5060 (the SIP port) in order to see if SIP messages are sent to the server.
On server, you can install ngrep for the purpose of seeing if traffic from the phone comes there. The command would be like:
ngrep -d any -qt -W byline port 5060
If you don't see traffic coming to the SIP server, then might be a firewall or an ALG between the client and the server, or, a firewall even on client host or server itself.
If it is something in between (not on client host or server), then you should try to use TCP or better TLS.
Note that if you have the firewall on the server, you will see the SIP packets coming on the network, but they will be dropped by the kernel before getting to application layer. Typically on Linux you can see the firewall rules with:
iptables -L
If the SIP packets come to the server, then set debug=3 in kamailio.cfg, restart kamailio and watch the syslog file (e.g., /var/log/syslog or /var/log/messgaes) for kamailio-specific debug messages -- you should get hints of what happens during processing.