IP - Internet Protocol, the most commonly-used set of rules for dispatching data across a large computer network.

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Specifing ip address for outbound connections on a multi ip host

one of my servers (Debian 5.0.6) has two public ip-address on the same interface. This used to work well for months but suddenly it is using "the wrong" ip addresses for outgoing connections. This is ...
6
votes
1answer
991 views

How to prevent/firewall calls to AWS EC2 Instance Metadata API?

The AWS EC2 Instance Metadata API provides a lot of useful functionality. Anyone on the actual EC2 instance can make a call to http://169.254.169.254/ and see metadata for the instance the call was ...
6
votes
6answers
4k views

How reliable are IP address-based firewall restrictions?

On some of my production systems that need to be accessible outside of the LAN I will sometimes add a firewall restriction at the edge to only permit traffic on, say, RDP from a specific origin IP ...
6
votes
3answers
6k views

Find IP address of a device?

Open question: How to find the IP address of a device? As I understand, there are no guaranteed methods that work always, but there's a hundred approaches that work in specific situations, and I'd ...
6
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2answers
761 views

Failed SPF for email imported to Gmail because of client IP instead of server's in message when sent through SMTP from one local box to another

We have a linux (Debian) VPS with domain (let's say example.com with MX mail.example.com) that has SPF set up. There is dovecot+exim running. There is also Direct Admin on top of that. When I send a ...
6
votes
1answer
3k views

Bind process or user to specific IP (Linux)

I have 3 non-root users on my server, and I want to give to each of them the different IP addresses (I have multiple IPs on one network inteface). For example, user1 will have 192.168.1.2, user2 - ...
6
votes
2answers
7k views

Can the same wildcard SSL certificate be used on different IP addresses and/or boxes?

Example: Wildcard SSL certificate for *.example.com installed on two different boxes. hostEU.example.com A 60.70.80.90 hostUS.example.com A 200.210.220.240 I assume this is a perfectly valid ...
6
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1answer
2k views

If I change a router's subnet mask to one that includes the old one, will the hosts with the old configuration still work?

Currently I have a router that is addressed as 10.2.1.1 on a 10.2.1.0/24 network. All of my hosts have default gateway 10.2.1.1 with mask 255.255.255.0. I want to know: if I change my router to ...
6
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1answer
10k views

Keepalived for more than 20 virtual addresses

I have set up keepalived on two Debian machines for high availability, but I've run into the maximum number of virtual IP's I can assign to my vrrp_instance. How would I go about configuring and ...
6
votes
1answer
209 views

Domain Not Resolving to Forwarded IP

I've recently registered a domain name with GoDaddy.com and forwarded it to my web server's IP address. Now when I enter the domain name in my browser, my site appears as expected. The strange part ...
6
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1answer
255 views

Someone parked a domain on my server/IP - should I worry? [duplicate]

Possible Duplicate: Is there anything I can do about someone who has pointed their domain at my ip? I'm running a dedicated server with own static IP for a while now. Some weeks ago I ...
6
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2answers
11k views

Debian/OVH: How to configure multiple Failover IP on the same Xen (Debian) Virtual Machine?

I have a problem on a Xen virtual machine (running latest Debian), when I try to configure a second failover IP address. OVH reports that my IP is misconfigured and they complaint they receive a ...
6
votes
1answer
7k views

Make sshd listen to a specific interface

On my machine I'm using OpenVPN which use the tun0 interface. I want sshd to listen only on this interface. I know, I can specify the IP address to listen to in /etc/ssh/sshd_config with a ...
6
votes
4answers
4k views

Openvpn, forward packets very slowly

I rebooted my server, and an odd issue just came out. I am running on ArchLinux, the clients are Ubuntu, Android and Mac. The problem is that accessing the internet via the clients is slow, about ...
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0answers
82 views

Why do I need to assign static ip address to the bridge and not to the physical interface? [duplicate]

I have bond0 with two physical interfaces in it. Normally I used to assign static IP address to this bond0 to set up internet connectivity on the server. Now, because of LXC virtual guests, I had to ...
5
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3answers
465 views

DHCP range starts with 194.77.30. Could that lead to problems?

Just noticed that our Lancom router has a DHCP range of 194.77.30.50 - 150. Could that lead to problems? Because sometimes some devices can’t be reached (with static IPS above that range like ...
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5answers
4k views

How does a router get its IP address assigned?

I understand how a device connecting to a router (e.g. 72.73.74.75) gets assigned a local IP address (e.g. 192.168.1.5) using DHCP. BUT, how does the router itself get the IP address assigned from ...
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4answers
1k views

Server answers only on one IP. Why?

ifconfig -a eth0 Link encap:Ethernet HWaddr 00:25:90:60:1B:FC inet addr:10.0.47.42 Bcast:10.255.255.255 Mask:255.255.255.248 inet6 addr: fe80::225:90ff:fe60:1bfc/64 ...
5
votes
2answers
520 views

Embedded device configured with bad IP address, can I still connect?

We have an embedded device running Linux (2.6.?) that can no longer be accessed over Ethernet. Someone in the field gave this device the following bad settings to its ethernet interface: IP: ...
5
votes
5answers
5k views

Another domain name pointing to my server IP?

I was checking out my reverse-DNS entry of my domain the other day which is run from a dedicated server. I noticed that another person/company had their domain pointing to my server? I have no idea ...
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5answers
3k views

hosting IP change, how much downtime to expect?

i'm moving my hosted site (same host) to a static IP, I understand there will be some downtime due to DNS caching - does anybody have any tips how to minimize this time and to avoid my users seeing ...
5
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3answers
9k views

how can I find the default gateway of an ubuntu box

how can I find the default gateway of an ubuntu box
5
votes
1answer
545 views

Some visitors cannot access my website

I am receiving some reports from different clients in Spain, US and France that they cannot access my website, https://www.ultreyatours.com. They get a ERR_NAME_NOT_RESOLVED error saying the server ...
5
votes
6answers
12k views

Finding ALL currently used IP addresses of Website [closed]

What steps would you take to discover all (or close to all) IP addresses that are currently used by a website? How would you be as exhaustive as possible without calling a website admin and asking ...
5
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2answers
199 views

Can you use IP V6 for name server records

This might sound like a stupid question as I have a very basic grasp of DNS management, but I'm looking for a new VPS and most providers only offer one IPV4 address, which doesn't validate on ...
5
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3answers
15k views

Routing WIFI and LAN for specific traffic

I have two network devices aboard my macbook pro: WIFI (en1): Used for general traffic. Connects to an ip of 192.168.19.* via DHCP LAN (en0): Used for specific traffic. Connects to an ip of ...
5
votes
1answer
9k views

What does ifconfig promisc mode do, or promiscuous mode in general?

This is what man ifconfig has to say about it. [-]promisc Enable or disable the promiscuous mode of the interface. If selected, all packets on the network will be received by the ...
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3answers
3k views

How to scan local network for SSH-able computers?

I am often on one computer in my house and I would like to SSH to another one, but often don't know the IP address of the one I want to connect to. Is there a way, from the command line, to scan the ...
5
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4answers
414 views

How secure is limiting site access by IP? [closed]

I'm currently developing software which requires various remote sites to securely connect to our servers to access a basic webapp. Up until now, I've been working on a client/server VPN setup - it's ...
5
votes
1answer
39k views

What does 192.168/16 mean? [closed]

OK, this isn't really a server question in practice, but I'm pretty sure it has something to do with server management. What is this joke supposed to mean?: http://xkcd.com/742
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2answers
1k views

One IP address, two different countries [closed]

I was using multiple websites to determine the geolocation of an IP address, and ended up getting two different countries (on the same continent). What is the reason behind this?
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2answers
4k views

/etc/interfaces file for multiple gateways, same network? (linux)

I've got my ip routing table setup as I'd like it: # ip r s 10.1.248.0/24 dev eth0 proto kernel scope link src 10.1.248.11 default via 10.1.248.1 dev eth0 metric 100 default via 10.1.248.3 dev ...
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votes
4answers
6k views

Apache 2: SetEnvIf “IP Range”

In my Apache config I want to set an environment variable if I see that the visitor comes from an specific IP range. Currently I do it this way: SetEnvIfNoCase Remote_Addr "^194\.8\.7[45]\." ...
5
votes
2answers
3k views

What is the difference between “route” and “ip route”?

I tried to understand the networking tools on linux. I am confused now about what should I use to manipulate the static routing: "route" or "ip route"?: route - show / manipulate the IP routing table ...
5
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4answers
310 views

Remove IP with ip command in linux

If I add two IPs like this: ip addr add 1.1.1.1/24 dev eth2 ip addr add 1.1.1.2/24 dev eth2 and then I try to delete one of like this: ip addr del 1.1.1.2/24 dev eth2 BOTH IPs will be deleted ...
5
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4answers
5k views

Small Linux distro for use as server

I'm doing a development that requires multiple machines, in-order to check. Currently, I'm running Python code on a full-fledged Linux VM. This makes it hard for me to run more than 2 machines inside ...
5
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4answers
1k views

Resolving IP address conflicts on a LAN

We have our LAN set up with DHCPD providing fixed IP addresses to the systems. However we are facing IP address conflicts if some one connects a laptop and assigns an IP address belonging to another ...
5
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3answers
19k views

Redirect request to an external IP to localhost (emulate a server)

I got an application (no source code) calling a server (hard coded IP) and expecting an answer before starting (a kind of login). Cause the server is down half of the time, I want to create a dummy ...
5
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2answers
4k views

“cat /proc/net/dev” and “ip -s link” show different statistics. Which one is lying?

I notice that /proc/net/dev says eth3 has 1753 drops. ip -s link shows 0 dropped. Why is there a difference? Where is the different data coming from? Which one is correct? I've stripped the out extra ...
5
votes
2answers
3k views

Can I buy an IP address range without buying from or becoming a member of my regional NIC?

My company has been investigating the possibility of buying our own IP ranges as we're growing at a very fast rate. However, the cost of doing business directly with our local NIC is proving to be ...
5
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3answers
3k views

A tool to change the default bind interface for a given command?

This is somehow related to Change interface for doing a whois The differece is that I'd like to know if it's possible to specify the default interface only for a specific program - not system-wide. ...
5
votes
2answers
397 views

Ubuntu 12 crashed and took down network

We recently set up a new Ubuntu 12.04LTS server on our network. It's not fully configured so it's not doing much beyond sshd and a default apache2 install. But this evening it appears to have ...
5
votes
3answers
784 views

Redirection by IP causing infinite loop

I am working to transfer a server from one box to another and do a massive code update tonight. To do this I'd like to set up a redirection so that normal site visitors go to a holding page. But ...
5
votes
1answer
183 views

POST of MTU + ~798 bytes gets lost

I have a very weird issue with certain packets not arriving on the destination host. It happens when we transmit a POST that is somewhat larger than the MTU. We can reproduce it with this script: ...
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3answers
829 views

In Active Directory, what is the relation between IP, MAC, and OS?

I have one machine on which I want to run 2 different OSs, dual boot between Windows Server 2008R2 and 2012R2 (or others). I want to keep the same computer name, the same IP address, and the same MAC ...
4
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2answers
581 views

Is it possible to find the actual source IP of a packet with a spoofed IP header?

I recently came under a DDoS attack. It was a SYN flood using spoofed IPs. Is it at all possible to trace the attack back to the actual sending server?
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8answers
3k views

How do you keep track of which IP addresses are used on your network?

What tools are available for allocating and tracking which addresses are being used? Specifically, our issue is that sometimes an IP is taken for a VM and when we go to build new ones they're not ...
4
votes
5answers
4k views

Best way to use large IP blacklist to deny access to a web server?

Is there efficient and easy way to use IP blacklist (like this one, but perhaps 2-3 times larger, which can't be simplified to CIDRs much) to deny access to a web server (either lighttpd or Apache) ...
4
votes
4answers
700 views

What is the proper netmask for an alias IP address?

I did a lot of searching, but there seems to be conflicting info on what the proper netmask for an aliased IP address should be. Some of the conflicting info seems to be FreeBSD-specific. I'm looking ...
4
votes
3answers
20k views

Adding a second IP to Debian Server

I was given a second IP by my server provider. I am running Debian 5.0. I thought I knew how to add the IP to the system and configure with apache, but I have not yet been able to. The primary IP ...