Networking :: Invalid Query Packet - Destination Host Not Responding?

Jan 13, 2010

I am an 'experienced perpetual newbie' using Ubuntu 9.04. I know a little about quite a few things but nothing past intermediate knowledge so:I am trying to set up a simple LAN between 'rhino' ( and 'polly-laptop' ( My router address is

From polly-laptop:
sudo mount rhino:/home /media/rhinohome
polly-laptop can access rhino:/home fine.


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Networking :: Relay Raw ICMP Packet To Local Destination

Feb 21, 2011

On my system, I have built my own tunneling protocol, where I relay packets over a non-standardized but verified medium. What I do is capture the packets using iptables and NFQUEUE, relay them over my medium, and at the other end I reinject them using raw sockets. The packet going into the tunnel is exactly the same as the one coming out, verified. The problem is that this doesn't work for ICMP Ping (Echo Request) if the destination of the ping is the same as the tunnel endpoint. If the destination is not the same as the tunnel endpoint, the ping packet is rerouted and arrives as it should at the receiver, and the ping reply comes back to the sender. Does anyone know whats going on? Isn't it possible to send raw icmp to yourself? If not, anyone have an idea what I should do instead?

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CentOS 5 Networking :: Dell1955 - Get Destination Host Unreachable?

Jul 30, 2010

I have 5 1955 blades in an enclosure for an custom application cluster.All were running Centos 4.4 no problem.We wanted to start upgrading them cleanly to 5.5 so two of them got fresh installs of 5.5.The installs went well enough, no glaring errors.However they can only ping each other! The network settings are fine, no firewall or selinux. I'd run the info script but I can neither download it to them nor paste it in via kvm.Standard static entries, virtually identical to their 4.4 brethren. They ping each other so network drivers are fine, no built in switch configuration changes. It has to be some kind of network configuration issue that i'm just not seeing.

Edit* When i try and ping anything else, including the other blades, I get Destination Host Unreachable.

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Fedora Networking :: OpenVPN Configuration - Destination Host Unreachable

Mar 6, 2010

I have a problem with the Fedora 12 Network Manager - OpenVPN configuration. If I use the same configuration and manually start openvpn (as client) I get connected to the OpenVPN server and I can ping the network that I am accessing. With Network Manager - I get connected but when I try to ping is giving me "Destination host unreachable". The routing table looks similar except that when connecting with network manager is giving me on more route in table

Destination Gateway Genmask Flags Metric Ref Use Iface UGH 0 0 0 wlan0 U 2 0 0 wlan0 U 0 0 0 tap0 UG 0 0 0 wlan0

Where is the IP of the OpenVPN server. When connecting "manually" I this routing table

Destination Gateway Genmask Flags Metric Ref Use Iface U 2 0 0 wlan0 U 0 0 0 tap0 UG 0 0 0 wlan0

What I do wrong in Network Manager? If I try to delete the route with is disconnecting the vpn connection.

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Fedora Networking :: Unable To See Other Wireless Machines - Destination Host Unreachable

Feb 17, 2009

I've got a problem with 'seeing' other machines on my Network. I have two laptops both with F10 on them however I can't ping either of them. They can connect fine to the internet and ping the router, they are both on the same subnet with Firewalls disabled on both machines. When I try to ping it says: "Destination Host Unreachable". I've tried firing up Wireshark to see if that will give me any clue but even that doesn't show any packets whatsoever from the other machine across the Network. It's like they are completely invisible to each other.

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Ubuntu Networking :: Internet Connection In 8.04 Server Edition - Destination Host Unreachable

Jun 8, 2010

i have a problem with my internet connection in ubuntu 8.04 server edition. if i ping to: [URL]... i get: Destination Host Unreachable but when i ping to my gateway or other pc's in my network no problems occur.

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Networking :: Host Not Responding To DHCP Request?

May 18, 2009

I am running a 2 NIC system with the routing table for eth0 allows user access to the internet,etc. and eth1 routes to another private network (192.168.x.x). eth1 is configured to handle DHCP requests.When a device connected via eth1 boots, it requests an IP from the DHCP server. Using tcpdump, eth1 is receiving the request but is not offering a lease.dhcp.conf seems to be configuring the DHCP service correctly. and dhcpd is running.The host is running Red Hat Enterprise Linux (Server Edition) 5.1. Perhaps I need to modify fire-wall rules (or disable them on eth1 altogether)?

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Fedora Networking :: Connectivity Between Two Different Live IP Based Systems - Ping Error: "Destination Host Unreachable"

Aug 26, 2009

I have 2 live IP based Linux systems .


Both systems connected in same LAN based network . Both WAN live ips are connected through different modems. Problem is that , no system is able to ping or connect with other system with Live ip , though they are able to connect through LAN ip and both systes are accessable and also able to browse internet (google etc..) Ping error :-- Destination Host Unreachable.

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General :: How To Make BASH Script Yes / No User Input Query Terminate With 3 Invalid Inputs?

Mar 16, 2010

I have a BASH script which at one point asks the user a yes/no question. I want to make it so that if the user types in an invalid input 3 times consecutively then the BASH script will echo an error and terminate with exit status 1.

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General :: Making Packet Sniffer Using Raw Socket - Invalid Argument

Nov 16, 2010

I am actually making a packet sniffer using raw socket. Its just that when I use the command '
if((ioctl(rawsock, SIOCGIFINDEX, &ifr)) == -1)
to get the interface index...
Its gives me an error saying :invalid argument?

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General :: Cannot Access/ping Debian \ Gives Destination Host Unreachable?

Nov 27, 2010

I cannot access/ping my Debian server. I know the IP is right (ifconfig, route and ip addr) all gave me (route gave me cannot ping it from any computer in my netwerk, even when I try to ping it from my Debian itself, it gives me Destination Host Unreachable !(Wierdly, I can ping tho).I am using virtualbox when the netwerk options 'NAT' turned on. When I look at my /etc/network/interfaces/ the last line looks like:iface eth0 inet dhcpShouldn't their be some other stuff listed?

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Ubuntu Networking :: Send The Keys Or Value As The Packet Data (content Of The Packet) In Ns-2 (for Wireless Environment)

Jul 12, 2010

I am the new user to ns-2. I would like to know is it possible to send the keys or some value as the packet data (content of the packet) in ns-2 (for wireless environment).

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Programming :: Perl - UDP Server Receive / Send Packet To Host

Apr 1, 2010

I have found many examples out on the www for creating udp servers with sockets. The problem I am running into is after I receive the packet from a host I need to be able to send a custom made packet(I'm using RawIP / NetPacket to make my packet) back to this host. The only way to do this is seemingly through the send() function. This function however doesn't appear to allow me to specify which host to send my packet to.

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CentOS 5 Server :: Named Reports "NXDOMAIN" Error When Query From Local Host?

Oct 29, 2010

I set up a DNS server, and it works fine when being queried from other hosts.But if I query it from localhost (by using nslookup), it reports error:

** server can't find NXDOMAIN


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CentOS 5 Server :: Authenticate/Decrypt Packet Error: Packet HMAC Authentication Failed

Sep 17, 2009

I got a problem with my CentOS server. Somebody told me OpenVPN Requires different changes inside my firewall settings. That could be the problem why openvpn wont load..I receive this error on my CentOS panel when im trying to connect into the centos openvpn (with my winxp pc):

Thu Sep 17 20:31:36 2009 TLS Error: incoming packet authentication failed from 84.xx.62.122:2622
Thu Sep 17 20:31:38 2009 Authenticate/Decrypt packet error: packet HMAC authentication failed
Thu Sep 17 20:31:38 2009 TLS Error: incoming packet authentication failed from 84.xx.62.122:2622


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Server :: Avahi_entry_group_add_service_strlst("localhost") Failed: Invalid Host Name

Mar 2, 2010

I'm trying to set up Apache to do test dev, so I don't have a "fully qualified domain". If I enter the hostname as the ServerName in httpd.conf when I restart httpd I get the error_log message:

PHP Code:


Sometimes I can get it to work, but it won't run on boot and right now even when service says httpd is running I can't reach it from another computers browser.

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Networking :: Unable To Connect Destination IP?

May 20, 2011

When I ping the router, i get the following proper response.

[root@ ~]# ping
PING ( 56(84) bytes of data.
64 bytes from icmp_seq=1 ttl=62 time=0.860 ms


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Ubuntu Servers :: Smtp Relay - "invalid/host-not-in-DNS Return Address Not Allowed"?

Mar 8, 2010

I installed the citadel suite on ubuntu server 9.10 Email obviously works fine internally. I tried to setup a smart host to send my mail through as my isp(Verizon) obviously blocks port 25. I tried to send out the Verizon smtp server on port 587. In the Administration> Domain names and Internet mail configuration>Smarthosts.My smarthost entry on the citadel configureation page above was but after sending an outgoing email, it comes back with a "invalid/host-not-in-DNS return address not allowed"

I have also tried using gmail and a hotmail account with the respective smtp address's in but they come back with "Must issue a STARTTLS command first".I have researched both messages and come up with squat that has helped me.

I know that my mail will have to go out through a smarthost of somekind. So is am I on the right track with choosing verizon/gmail/or something else as my smtp relay, or is there a free service out there that I can send email through(haven't found one if there is)

Anyone else ever setup Citadel and got around their isp blocking port 25?I am also not sold on citadel, it was just the first/ nicest looking one that I found.

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Ubuntu Networking :: Transfer Files From Cluster To Host And Then Host To Another?

Mar 4, 2010

I am working on a cluster for a molecular dynamics class and I have to edit my FORTRAN code (only the newest and best for me!). In order to get through to the cluster I have to ssh in. The network on which the cluster resides is behind a firewall, so I have to ssh through the firewall into the network first.

this is fine, I can login and move files and folders as needed, including sftp-ing into host 1, then into the cluster so I can transfer files from cluster to host and then host to me. This gets rather tiresome, so it would be nice to edit the files in place.

The problem is that when I access my code with emacs it launches the emacs client on Host 1, with no mouse support. I know the purists will howl about how I should be using keyboard shortcuts, but I am a chemist and not a programmer, so the mouse is very nice for me. Is there any way I can perhaps mount the cluster using sshfs so that when I open my code it launches a local instance of emacs? Sorry if this is the wrong forum, but I thought it was network related.

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Networking :: How To Find Least Busy Host Given Hardcoded Host List?

Oct 12, 2010

I got a bunch of machines (~10) that I share with my co-workers. I have appropriate .ssh file(s) set up so I don't get prompt for password when I try to ssh.Currently I ssh into these hosts and then do a top to check the load before I start using the machine. Because I don't want to be on a busy host.Can someone show me how to write a script that find a least-busy host given a list of hosts to check? (hardcoded is fine)

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General :: Error "invalid Arithmetic Operator" When Telnet To Local Host ( Via A Personal Port

Feb 12, 2011

i write this script:


i make this script to become a service ( i test it from bash, and my script work good), my problem is when i telnet to my local host ( via a personal port like 5555 telnet give this error: ")syntax error: invalid arithmetic operator (error token is ", i know this error is for echo $(($A+$B)) and i know that telnet can not calculate $A+$B and the error is for this

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Networking :: Possible In Iptable \ Switching Destination IP To Source?

Sep 16, 2010

Using iptables is there a way to switch the destination IP to become the new source IP and forward that connection.iptables store the src and dst IP in a variable for a particular connection?

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Networking :: Very Low Network Performance In Host-to-host Connections

Jan 27, 2009

The internal network is behind nat done by the PC Router.The TP Link is recieving wireless signal from outdoors and it has switching and basic routing capabilities. I'm using the PC router for better routing options.PC Router (or R for short) is a triple-booting machine - Linux, FreeBSD and Windows. It has two lan cards - external (ext_if) - 100Mbps Realtek 8139 and internal (int_if) - 1Gbps integrated Realtek 8169.The problem is that all traffic from R to the network is slow - about 5-20K, while the traffic in the oppoiste direction is all right - about 10MB that is fine for 100Mbps cables, NICs and switches. The problem persist no matter the OS the pc R is running.I've tried some debugging on the situation as follows:

- put another PC at the place of R - everything is fine. That exclude the possibility of damaged cables, RJ-45s, switches and etc.
- connected both of the NICs to the Internet while the internal network is being disconnected and they both work fine (no delays)
- traffic shaping is not running
- there is nothing in firewalls except NATing the internal network (and it is working fine). Actually these firewall rules have been operational for more than months and everything was fine untill a week or two ago.
- changed the internal NIC with another
- connected the internal network directly to the TP and all of the PCs are getting good network performance. Then connected the R machine to the TP as well and there was good performance between the internal network PCs and R.
- R has good performance to the TP. In fact everything has good performance directly to the TP (when not connecting trough R).
- the problem persist only between R and machines from the internal network.

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Ubuntu Networking :: Shaping Banwidth According To Destination Mac Address?

Jan 20, 2010

I'm trying to shape bandwidth using HTB method and filtering classes with destination mac address. for this I've found two codes but none of them seem to filter bandwidth as i want (test with iperf) can some one explain me the problem with theses codes

tc qdisc add dev eth0 root handle 1: htb
tc class add dev eth0 parent 1: classid 1:1 htb rate 1000kbit ceil 1000kbit
tc filter add dev eth0 parent 1: protocol ip prio 3 u32 match u16 0x0800 0xFFFF at -2 match u16 0xM4M5 0xFFFF at -4 match u32 0xM0M1M2M3 0xFFFFFFFF at -8


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Ubuntu Networking :: Using Iptables To Change A Destination Port But Keep The Ip The Same?

Mar 23, 2010

I am playing around with transparent proxies, The current way I am doing things is the program makes a request to a computer on port 80, I use

iptables -t nat -A OUTPUT -p tcp --destination-port 80 -j REDIRECT --to-port 1234 to redirect to my proxy that I am playing with. the proxy will send out a request to port 81 (as all outbound port 80 are being fed back in to the proxy) so I want to do something like

iptables -t nat -A OUTPUT -p tcp --destination-port 81 -j DNAT --to-destination xxxx:80 The problem lies with the xxxx part. How do I change the destination port without changing changing the destination ip? Or am I doing this setup completely wrong,

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Networking :: Sending Messages Through Alternate Routes To Same Destination?

Jan 11, 2010

I am doing a university course and am struggling to find a method of sending 1 message down route A and then the next message to the same destination via route B, alternating between the two with each new message sent.I am going to use a Linux computer with two Ethernet cards connected to two different networks via a routers and then to the destination host via a switch.

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Networking :: Query Regarding Libnetfilter_queue Usage?

Jan 7, 2010

I am writing an application using libnetfilter_queue that should perform the following function- Receives packets from NFQUEUE- Apply a decryption algorithm to packets- Issue an ACCEPT verdict for decrypted packetsThese packets are destined to another box behind the firewall running the above mentioned application.Based on Fig 14-1 from the link belowI intend on siphoning out network packets at the PREROUTING chain of the Mangle table by usingiptables -t mangle -A PREROUTING -i eth0 -p 1234 -j NFQUEUE1) I would like to know if the PREROUTING chain in the mangle table is an appropriate place to pick off the encrypted packets ?2) Once the ACCEPT verdict is issued will the modified packets resume processing along the PREROUTING chain of the mangle table ?3) Is there a well documented reference for API's that i will need to use while developing this application ?

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CentOS 5 Networking :: Uber Frustration With Network (Destination Not Reachable)?

May 31, 2010

i don't understand what I am doing wrong. I started a CentOS Vm through Vmware server 1.05 When I run the machine I preform Dhclient and my machine gets an IP internet works fine.

When I change my IP to static everything stops working I cant ping anything anymore I cant ping my server I cant ping my gateway I cant ping google My config is done through Webmin but I know it can also be done through /etc/sysconfig/network-scripts/ifcfg-eth0 My hosts file has this localhost srvspam
my /etc/sysconfig/network-scripts/ifcfg-eth0 file has this


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Ubuntu Networking :: Host Able To Ssh To FreeBSD Host?

May 19, 2010

So here's the setup:

Ubuntu 10.04 host inbound port 22 open
FreeBSD 8.0 host no inbound ports open

Both hosts are running sshd currently. What would you do for the Ubuntu host to be able to ssh to the FreeBSD host? A tunnel?

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Ubuntu Networking :: 9.10 Updates Yesterday/Today Cause Packet Loss On Networking

Apr 9, 2010

I have 3 Dell Precision M4400 machines. After getting updates yesterday or today, I get random network dropouts like crazy, on wired or wireless. On one machine I was able to turn off ipv6 in grub and reboot, and it works now. However on the other 2 machines, still have the same problems. All 3 are running 9.10 64 bit. Is there a way I can back out the updates so the network works again? Anyone else see this behavior after updates today?

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