One of our application sends messages to the MSMQ that runs on the same server.
Code reference it this way in our Production environment (Note it uses the IP).
net.msmq://123.123.123.123/private/LoggingBiz/Logging.svc
We are building a secondary system and this part of the application did not work.
When we changed it the reference (in URL) to hostname it started working:
net.msmq://hostname/private/LoggingBiz/Logging.svc
When I was talking to the developer said that it might that the MSMQ does not use IP address. But it works in Production, so I am reluctant to accept theory.
I think it is environmental.
Can someone suggest what could have been gone wrong?
Regards,
RM
The hostname will just be looked up to find the IP address using DNS so I think your developer is wrong.
The IP address is then used to lookup a MAC address so if the IP is not working then I suggest there is a problem with the ARP table on the machine.
you could try clearing the IP from the ARP cache:
arp -d <ip address>
Example
arp -d 10.1.1.2
Related
I've got a cheap openvz Ubuntu vps and i'm trying to run my own dns server on it for learning purpose.
The dns server works fine in localhost (on the vps through ssh), i can query it using dig google.com #127.0.0.1 and i get the expected result (which is not the IP of google.com but a custom one).
When i try to query the dns server from outside the vps, using the same command, I do get a reply but the IP is not what I expect (it's an actual google.com IP).
After further investigation I found out my dns server is not receiving/sending packets when the query is done from outside the vps. So the answer is sent by something else, it seems like inbound packets with destination port 53 are deviated, they do not even reach my dns server.
I tried to query my dns server, still from outside, but this time while the VPS was SHUTDOWN. Magically i got a reply from god knows who.
Changing port from 53 to 54 everything works perfectly.
The problem is i need it to use port 53.
I don't have iptables rules nor any other firewall doing something related to port 53
I also tried to query some other random vps, from different hosting providers, seems like everyone has a dns server running! Why does everyone reply?
Of course i asked technical support, that's what they said:
Hello,
Sorry but we don't do "software" technical support on VPS.
We deliver the hosting and the operating systems, customers that order VPS are their own admins, and have to know how to manage a linux server.
We don't block any port on our side.
Best regards,
Support
Mybe your dns server is bound to the loopback interface only (so it's only listening on localhost). You can check the current service ports used (udp for DNS) using netstat and filter (grep) udp port used
netstat -an | grep ":53"
Also you can test the same dns query using the nslookup command, and checking the dns server ip that answer your dns query, in the result output:
nslookup google.com [dns_server_ip]
Also test it without dns_server_ip to check if there is a default nameserver when the specified nameserver is not responding.
Problem solved, it's my ISP intercepting and replying to dns queries.
I can do dig google.com #1.2.3.4 and i get a reply :D
Who wants to know more about this:
ISP Intercepting DNS Lookups
Last several days I'm struggling with a problem.
I have two instances(ubuntu server) on gcloud and I want to assign them their external IP.
And I can ping and ssh to my instances but when I try to do telnet it is not performed.
On gcloud all instances have one internal ip and one external IP.
And they does not know their ip. I get it from gcloud console.
How could I assign it to them?
Also I've tried sudo ifconfig eth0:0 130.211.95.1 up
You can do something like this to add the external IP to a local interface:
ip addr add 130.211.95.1/32 dev eth0 label eth0:shortlabel
Replace 'add' with 'del' to remove it once you are done with it.
shortlabel can be any string up to a certain (short) length.
Update: also see this GCE support issue for related information.
A feature request for this is already filed on GCE public issue tracker, however it is not yet implemented. You can star it to get notification if any update posted on the thread.
May you also mention what's your use case? so I can probably provide you with a workaround.
i am having problems with wget on linux. After little research i found out that i cant get reply from dns server.
But its really strange because other windows machine (in same network switch) can access the dns.
Wireshark gives me info about that linux machine is sending arp requests for dns into network but cant get reply from it.
On windows machine it seems like that it doesnt send arp request for dns servers, but it just send to dns ip address with mac of default gateway which could be resolved by arp on both machines.
What could be wrong?
linux ip is 10.20.5.1 mask: 255.255.252.0
default gw: 10.20.4.1
dns addresses on: 10.230.6.12 10.230.6.13
Not really a programming question but I'm curious.
You're not on the same network as the dns servers so if you want send traffic to the dns you have to go through the gateway hence I would expect an arp request for the gateway and not for the dns
If your machine is really doing arp for the dns address then that makes me believe that your netmask is not what you say it is (maybe not configured hence /8 -- the std for a class A network)
Can you output:
ip a sh
ip route get 10.230.6.12
Rgds
MArcel
Perhaps someone has some help? I am running dnsmasq on Ubuntu 12.04 LTS. This server's address is 192.168.15.3. My gateway's DNS is 192.168.1.254, that takes me out to the Internet. I also have a special-purpose DNS at 192.168.15.2. So I wanted to give those 3 name servers to DHCP clients. This is my dnsmasq.conf server= section:
server=/localnet/192.168.15.3
server=/localnet/192.168.15.2
server=/15.168.192.in-addr.arpa/192.168.1.254
However, when I look at the DHCP allocation on a client, I see only 192.168.15.3 as the sole DNS server. Clients cannot access the Internet (the NIC on .3 is configured correctly and can access the Internet from its console login).
Granted, the first server= line is probably not necessary, but I added it thinking it may help, didn't.
What am I doing wrong? Thanks for your help!
OK, after MUCH experimentation, I found I had to push the option manually. In the dnsmasq.conf file, I added the following line:
dhcp-option=6,
like so:
dhcp-option=6,192.168.15.3,192.168.15.2,192.168.1.254
This served the correct list of name servers to DHCP clients.
The server lines are configuration for dnsmasq's own DNS server, about where it should forward DNS requersts that it receives in order to be able to resolve (and cache) them.
Only the dhcp-options are part of the DHCP configuration that get passed to DHCP clients - so, the accepted anser is correct, but I wanted to share why.
I've been developing locally on a little ubuntu netbook with xampp for about 7 months. Two weeks ago I got a computer I'd like to use as a server. I've installed the latest Ubuntu distribution and xampp, moved all my files over, and forwarded port 80. I've also got a domain name from dyndns.com which is being updated by a client which runs in my router (a Netgear WGR6154 v8).
Now, when I try to access my server by typing in the address I got from dyndns.com the browser loads until it timesout. I can access everything locally using localhost as the address so I believe xampp is running, just unable to connect with the internet.
In order to be able to view my files over the internet what should I do next?
Thanks to all in advance...
[I'm starting a bounty for the first person to help me get my files successfully online]
You have a combination of issues here, and that is something of a problem. Each issue is complex in an of itself. Here is what I would recommend to get you going for certain.
First verify that you can surf the web from your server. This will confirm that you have a working ethernet interface.
Step 1 make sure that XAMPP, and your files are viewable from your home network. I assume you are using something like 192.168.1.X for your network and perhaps your server is 192.168.1.10
Go to another computer in your house and type http://192.168.1.10/ and see if you can see your files. If you can then you know that the server is properly configured and XAMPP is working.
Then add an entry to your hosts file to resolve yourdnsrecord.com (or whatever your dyndns record is) to your private ip address. Then when you type yourdnsrecord.com into a browser from that computer you should still get your files. This will rule out your server being improperly configured to listen for that domain name.
Next you need to test to see if there is a firewall problem. To simplify this, first remove your home router from the equation. Instead, place your new server directly onto your internet connection. (assuming you can). This way, you do not need to have NAT or firewalls properly configured. Your dyndns name should map to a public IP and your server should then have that IP and be connected directly to the Internet. If you have your server directly connected, and the command ifconfig from the root prompt returns the same public IP address that your dynamic dns record is point to, then it should work.
It will make your life easier if you have an iphone or some other way to test how your network is seen from the Internet.
If your public IP as shown by ifconfig is different than the IP record in your dyndns account, then your dynamic dns update script is broken. manually set the IP, and see if things work.
It is very possible that this will not work. Some ISPs firewall port 80 preventing their subscribers from hosting servers. Once you have your server directly connected to the internet you can test this (even if your dns is not working) by using the public IP address. As root, type ifconfig from the command prompt to get your public ip address. Then type the command tcpdump -i eth? port 80 from the root prompt. eth? needs to be the same interface that you saw had a public IP address from the ifconfig command. usually this is eth0 but it might be wire0 or something like that.
This command will show you all traffic coming on port 80 to your server.
From an iphone (or whatever second Internet connection you have) browse to the IP address that you got from your ifconfig command. If you see something on your server (and it is directly connected to your ISP) then your ISP is not firewalling you.
If you can get to your server, when it is directly connected to the Internet, either by IP address or by DynDNS address, then your ISP is OK and it is time to debug your firewall.
Two things need to work for your firewall to be configured NAT, where the public address that your router gets from your ISP is converted into your private network and a firewall rule which permits that traffic. If you get this far, then you know your firewall is the problem and then it is just a matter of getting its configuration correct. There are far to many home routers to document here, but you usually can find how-to instructions for your router for this task from the manufacturers website (usually it is part of the manual)
If you follow these instructions exactly you will get your system working. Make comments on the process and I will be happy to modify this to make it clearer.
HTH,
-FT
You should make sure your xampp is not listening to only the localhost.
to do so edit your apache configuration file and check and search for Listen directive
you should be able to know also by analysing the output of netstat -a.
After that make sure your router is forwarding properly, using tcpdump would help.
drop me a comment if you need more help.
Cheers