I am currently using vps in hostinger. My problem is that my ipv4 can't able to fully propagate in my PTR Record. Only the ipv6 can. What do i need to do to fix it? Since i am looking to increase the improvement of the deliverability of my email in google from my mail server
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I've been poking around the internet trying to get an answer to this one but so far I've only seen it as "normal" behavior.
I have a fedora 29 host configured to send rsyslog messages over the default 514 port. That works as intented and has been for some time now. I had a client notice that the host would "listen" on an ephemeral port that appears to change with each reboot:
ss -tulnp | grep 46852
udp UNCONN 1536 0 0.0.0.0:468520.0.0.0:* users:(("rsyslogd",pid=676,fd=15))
also:
lsof -i :46852 -P
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
rsyslogd 676 root 15u IPv4 24836 0t0 UDP *:46852
Anyone know why rsyslog is doing this? It appears to be default behavior, and I'm not worried about it as the port can't be hit externally (firewall prohibits it) but just wanted to understand it. I also couldn't find anything in the rsyslog docs that talked about it.
Thanks!
This is just observed behavior I am curious about.
This isn't something that rsyslog is doing, but rather your OS.
Clients are assigned port numbers (random and sequential) by your operating system, as part of the sequence of system calls, that create a network connection. For example TCP and UDP typically use an "ephemeral" port for the client-end of a client–server communication.
These port numbers are - as you said - called "ephemeral" because they are valid only for the life of the connection and have no special significance.
As to why ephemeral ports are used.. I don't know. Maybe someone on ServerFault or Network Engineering can answer this question.
From my understanding ephemeral ports can be used either temporary or private. So if a service (temporarily) needs a port it can use an ephemeral port. After the service has done it's requests and has timed-out for some time, the port is released and can be used by some other service. This way a service doesn't block a port even though it doesn't even use it, or just frequently uses it.
I'm tring to test my Windows Phone 8 app on an actual device, but I need the IP Address of my computer in order to do this. When I type 'ipconfig' in the command prompt, it shows two different IPv4 addresses and I can't tell which is the correct one for my computer that will allow me to test the app on a device.
Command Prompt Output:
Ethernet Adapter vEthernet <Internal Ethernet Port Windows Phone Emulator Internal Switch>:
IPv4 Address......: 169.254.xx.xx
Ethernet Adapter vEthernet <New Virtual Switch>:
IPv4 Address......: 192.168.x.xxx
I'm having a heck of a time getting this app to actually work on a device so if there is anything you see that is off, by all means let me know. My concern in this question though, is which of these is the true IP Address of my computer?
The one starting with 169.254 you can safely ignore. If a device does not receive an IP from any DHCP server within a few seconds, it creates its own, starting with 169.254.x.x, but you can't reach anything with such an IP, nor can anything reach your device.
The second one is the real one in your case. 192.168.x.x means you are part of a private network (but it could also be 10.x.x.x).
If you see multiple IPv4 addresses listed in command prompt as a result of ipconfig command, then the IPv4 address that has Default Gateway is your main or current device or computer IPv4 address.
The first one is your computer's IP address, the second one is for application or OS virtualization.
I've looked through posts with no real answer to this question: is the address 127.0.0.1 a hardware set address much like promiscuous mode is a hardware setting on devices? I've tried to set my address to 127.0.0.1 on eth0, disable the lo, and even change the lo address, to make packets go out the eth0 port with address 127.0.0.1. The packets always end up on the lo port when I use sniffing tools like wireshark. Is there a way to do this, is this hardware or hardcoded into the drivers?
The loopback address is controlled by software (e.g. in the kernel). It is never associated with any hardware.
You don't specify your operating system, but unless it's very unusual, there really isn't a way to do what you ask (have packets addressed to 127.0.0.1 appear on an external interface).
Update:
Here's the spec:
127.0.0.0/8 - This block is assigned for use as the Internet host
loopback address. A datagram sent by a higher level protocol to an
address anywhere within this block should loop back inside the host.
This is ordinarily implemented using only 127.0.0.1/32 for loopback,
but no addresses within this block should ever appear on any network
anywhere [RFC1700, page 5].
Assume that there is a web-page called whatisyourip.com and that I have a web-page called changeip.com. A user wants to enter the site whatisyourip.com through changeip.com. Normally, changeip.com would be a proxy server so the user can hide his ip address. That's how users reach forbidden web-pages in their countries. But I want to ask, is there a way to show a different ip address to whatisyourip.com while connecting it through changeip.com without using it as a proxy server?
is there a way to show a different ip address to whatisyourip.com while connecting it through changeip.com without using it as a proxy server?
Short answer: Yes. Make changeip.com a VPN server and assign different IP addresses to those VPN clients. Ensure they send all traffic through the VPN. This usually involves modification of the local routing table on the VPN client workstations for everything to work correctly.
Longer answer... There are several reliable ways to hide IP addresses of TCP sessions...
HTTP Proxy - you already described this situation
Network address Translation - this doesn't sound likely in your scenario
VPN Tunneling - Possible solution instead of HTTP proxy, even if it's something as simple as an SSL VPN. Depending on your constraints, this could also be a viable option.
You can't. TCP connections require a 3-way handshake. You can certainly send a SYN packet to the server to start the process, then change your IP address. but when the site responds with the 2nd-stage of the handshake (SYN+ACK), that packet is now going to your old IP address and your system will drop it - it has no idea that the server is responding to something that was started on the old IP.
You could try something like the Tor network, which offers end-to-end encryption of traffic and cloaking of origins, but it's not something I'd consider "reliable".
Not unless you spoof your IP, in which case the response will go to the forged IP. So no.
Is there a performance difference between TCP connections to:
localhost / 127.0.0.1
a domain which resolves to the local machine
Or more specifically, do the latter connections go through the loopback device, or over the actual network?
The reason I'm asking is I'm thinking about changing database settings in many PHP apps so they use a full domain instead of localhost. That way we could more easily move the database to a different server, if the need arises.
This is implementation and operating system dependent. On Windows, anything connecting to a local IP address, even if it is an outside-facing IP, will go over loopback. This is a documented problem for applications such as packet sniffers, because you can't sniff the loopback. (Windows doesn't treat loopback as a "device" -- it is handled at the network level.) However, in this case it would work in your favor.
Linux, in contrast, will follow whatever you have in your routing table, so packets that are destined to your local machine will go to your local machine over the network if the routing table isn't properly configured. However, in 99% of the cases the routing will be configured properly. Your packets won't go over the loopback device, but the TCP/IP stack will know that you are contacting a local IP and it will virtually go out and back in the proper ethernet device.
In a properly configured environment, the only bottleneck for using a domain name would be DNS resolution time. Contacting an outside DNS can add additional latency into your configuration. However, if you add in the domain name into your /etc/hosts file (C:\Windows\System32\drivers\etc\hosts on Windows), your system will skip the DNS resolution phase and obtain an IP directly, making this time cost moot.
That depends on how the names are resolved. The procedure is typically /etc/hosts first and then DNS if that fails. If localhost is in your /etc/hosts, putting whatever.wherever in the file as well will make it resolve with the same speed.