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Questions tagged [firewall]

A firewall is a program that controls the incoming and outgoing network traffic on a system. Use this tag for all questions related to firewall configuration and operation.

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Why am I getting connection refused with IP address even though it works with localhost and firewall is open?

When I run sudo ufw status on a Ubuntu box, I get the following output sudo ufw status Status: active To Action From -- ------ ---- 22/tcp ...
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How to tell which application UFW is blocking

I have a Debian system running ufw. I have "default deny" on all outgoing connections and I open specific communications (ports and/or IP addresses) as needed. I use the dmesg log to see if ...
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How to update, instead of flush and re-write, iptables rules

Currently I'm updating my iptables rules using a bash script, where I call the command: iptables -F then I apply the rules. The problem being that I need to update the rules to gain access to port 80,...
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Server timeout if 2 devices are used in the same network

I have 2 devices: a computer and a Android smartphone on the same network, if a do like 10 requests on my server with my Android phone, I have a timeout when I try to do the request with my computer ...
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UFW is Manually Disabled via Shell - Can the system re-enable it on boot?

Take note i am already aware how to have start the ufw service on boot. This is not what i am asking. So, right now, if i check ufw status it shows as "Active". And when i reboot and check ...
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Why does traffic continue to flow through my gateway despite a firewall rule blocking all outbound traffic addressed to it?

While messing around in a qemu guest I discovered something very peculiar. If I set the system firewall to reject all traffic to my gateway (10.0.2.2), the firewall only rejects traffic destined to ...
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How to connect a CUPS printer to a Fedora box through a firewall?

I have bought a new printer and connected it to my LAN/wifi with an Ethernet cable and I can access the printer from my phone. But when I try to add the printer to CUPS on a Fedora box that is also ...
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Ping, SSH failed in VM and host machine

In VMware from Centos to other VM and windows host ->ping and ssh not working(prompt does not say anything,it goes to timeout) from Centos -> google ping is ok, from other VM to Centos -> ...
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How to limit web usage with nftables?

Between certain times, I would like to limit the amount of internet browsing I can do to force myself to focus (something like visiting ~3 sites per minute). This is what I came up with: table inet ...
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how to get around the firewall when connecting to the remote server

I want to connect to a remote computer and start Jupyter notebook on the remote computer. Every time I try to connect to jupyter notebook there is an error. When I turn off my firewall the jupyter ...
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How do i convert iptables rules to nftables rules?

I was trying to figure out how to convert my iptables rules to nftables rules on an Ubuntu system. I tried to convert iptables to nftables using the automated converter, but it didn't appear to work. ...
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How to reset the firewall configuration in a persistent manner?

Internet works, ping 192.168.1.4 which is for sure of an Android device does not. I believe it is an issue of the firewall programs. $ ping 192.168.1.4 PING 192.168.1.4 (192.168.1.4) 56(84) bytes of ...
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ufw not logging all connections as expected

I am trying to setup logging on ubuntu server 20.04.4 using ufw, but I'll take non-ufw advice as well. I am running a test https server on port 20000 and want to log all connections to it. Here's what ...
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Is there something I can execute via the CLI, to show the presence or absence of an ERR_CONNECTION_RESET when attempting connection to a domain/URI?

Is there anything I could I execute from a linux command line from 2 different linux clients, in 2 different locations, that may show the presence of absence of an ERR_CONNECTION_RESET message (or ...
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Vnc not working on fedora (tigervnc)

Vncviewer is always stuck on "detecting 4 decoder threads", I tried 3 servers (the official one using systemd, x11vnc, and krfb). Also using the official guide I adjusted the firewall.
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How can I block a port being used by docker?

I am running wikijs on port 8080 running reverse proxy with apache. With cloudflare argo tunnel so only specific people can login to wikijs. So if user try to browse http://publicip:80 (port being ...
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nftables rate limit whitelist

Following this article on nftables Blocking IP addresses that attempt more than ten new incoming TCP connections within one minute how would one add a whitelist like ip saddr != { ip1, ip2,... }? ...
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Kubuntu 21.10: All ports (open or closed) return ICMP admin-prohibited, even with no firewall enabled. How to fix?

Running an up-to-date installation of Kubuntu 21.10. If I run any network service on the machine, I'm unable to reach it from anywhere else on my network. The error is always "Host unreachable&...
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What is the relationship or difference among iptables, xtables, iptables-nft, xtables-nft, nf_tables, nftables

I have been reading for a while now. What I understood is: nftables is the modern Linux kernel packet classification framework. nftables is the successor to iptables. It replaces the existing ...
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ufw won't allow connections to postgres port 5432

With ufw disable on remote postgres system i'm able to connect from my local system However, the connection does not work when I ufw enable as shown below: C:\Users\HOME>telnet 80.240.24.195 5432 ...
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iptables blocks loopback traffic to docker

I am running a docker container with -p 4880:80. When accessing this service via curl against 127.0.0.1 or my public ip from the host, I get a timeout and with tcpdump I see no traffic on the docker0 ...
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Problem with server - client connection

I run PyCharm on a Debian 11.1 machine and I want to use the Remote debugging with the Python remote debug server configuration. In this debugging procedure PyCharm emulates a server which connects to ...
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INVALID_PORT Error from firewall-cmd

When I try to add a port via firewall-cmd --permanent --add-port=XXXXX/tcp I get the error Error: INVALID_PORT: XXXXX Why?
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How to block all incoming connections except one country using firewalld or iptables [duplicate]

I found country IP list: https://www.ip2location.com/free/visitor-blocker I tried to drop all then add the iptables from that list but it didn't work, can I get some help? Thanks.
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nftables refuses to add chain

I am trying to run the following nft commands: nft add table netdev filter nft -- add chain netdev filter input { type filter hook ingress device vlan100 priority -500 \; policy accept \; } nft add ...
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Firewall is active, added port to iptables but still cannot connect

We have RedHat 8 server. Firewalld is active. I need to connect to port 5050 from my lap top and from the second server, so I added it to the rules iptables -I INPUT -p tcp -m tcp --dport 5050 -j ...
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iptables/firewall-cmd DROP rules set last block ip rule set before

As follow is the list of the iptables rules that I have : # firewall-cmd --direct --get-all-rules ipv4 filter INPUT 0 -p tcp -m state --state NEW -m tcp --dport 22 -j ACCEPT ... ... ipv4 filter INPUT ...
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How to allow packets for WS-Discovery (onvif)?

I have a Linux machine with ufw firewall, a program runs WS-Discovery that works as intended when ufw is disabled but fails to return anything when it is enabled, what I tried without success: ...
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How to prevent external IPv6 adresses from pinging my Adress IP address

How to prevent Extern ipv6 adresses from pinging my Adress? I am able to ping the others but i want to prevent the others from pinging me. i have written the Following Script but it does not do the ...
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how to use firewalld in stateful mode

I have to setup an stateful firewall on centos8 using firewalld. I'm new to firewalld but have experience with old style iptables for this purpose. since it is recommended by Redhat here, I prefer to ...
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Connection refused between 2 linux containers

On my host Ubuntu 18.04 I am running two lxc containers using default setups. Containers use Ubuntu 18.04 as well. I have an app running on container1 that offers an https based service on https://...
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Ufw allow app: ERROR: Need 'from' or 'to' with 'app'

I am using Ubuntu 20.04.3 LTS, although this question is probably not specific to Ubuntu but to any system using ufw. I am setting up a rule for VNC vino connections. I meant to do that via a ...
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Does UFW reset iptables on reboot?

I connected to my remote Linux server to adjust my network settings, but I accidentally changed some rules using iptables instead of my preferred method, ufw. I added the rules in ufw and then ran ...
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What is missing from these Oracle Solaris 11.4 firewall rules to allow traffic

I am trying to reach a separate, in-house application server from our Solaris server. The only firewalls that exist between these two are the native firewalls. We have set the following rules on the ...
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iptables Forwarding and port blocking

I have created the following Network in Virtual Box: Linux Internal PC with 1 Static IP: 10.10.10.2 Linux Gateway/Firewall with 2 Static IP's and 1 NAT: 10.10.10.3 | 11.11.11.2 | NAT Network Card ...
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Unable to connect telnet to mysql listen ip port from remote host

I m able to telnet locally to mysql process like below: I have also made sure MySQL process is listening on all IPs by setting bind-address = 0.0.0.0 as evident below: root@localhost:~# netstat -plutn ...
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IPTables - 2 Nics - Private - Public - Private route

I have a CentOS 7 with 2 NICs (enp1s0 - private LAN 192.168.0.0/24 and enp0s29u1u1 - public) that I use as a gateway / router via iptables. All PCs on the private LAN connect to the internet via the ...
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EHOSTUNREACH error creating a TCP connection between instances on the same EC2 subnet

I have a client EC2 instance and a server EC2 instance, both residing in the same EC2 subnet. The subnet routing table is configured so that this is a “local” route. When I run EC2 networking ...
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Why do boottimes differ daily?

My boottimes differ on a daily basis ( in Kubuntu, which I use as a daily driver ). Sometimes the BPFilter ( UFW ) will start displaying errors for about 10 seconds. Sometimes it doesn't. Sometimes my ...
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Configuring the firewall with iptables

I have an instance of SSH running port 2233 and a Cowrie honeypot on port 2222. SSH needs to stay that way but Cowrie needs to be forwarded to port 22. Port 2222 (running Cowrie) shouldn't be visible ...
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Consequence of blocking outgoing UDP 68->67 (DHCP client)?

I have a server that receives its IP address by DHCP. This seems to work and the connectivity is working (at the moment). However, I have not rebooted since installing a new /etc/sysconfig/iptables ...
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Ubuntu 20.04, Firewalld: Am able to SSH from outside of Source Address

So I'm going through the setting up local firewalls on linux servers for work. Today I created two new zones: zoneA and zoneB. Zonea has snmp and ssh services added, also has 4 subnets and 1 ip ...
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What's the idiomatic way to allow incoming connections on a TCP port, as of 2021?

It's been years since I last fiddled with firewall rules; and I remember the iptables chains for input, forward and output, and their various rules. But the times, they have a-changed, and today ...
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Is my firewall configured OK?

$ systemctl status ufw ● ufw.service - Uncomplicated firewall Loaded: loaded (/lib/systemd/system/ufw.service; enabled; vendor preset: enabled) Active: active (exited) since Sun 2021-10-03 15:43:...
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Is it possible to block website through system Linux firewall for browser that used DNS over HTTPS?

OS: Fedora 34 Browser: Mozilla Firefox with DoH enabled I'm trying to block website through core Linux settings (not web browser extension etc). Problem is inside DoH that I'm using. If I disable DoH, ...
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If I remove `ssh` from public zone and retain only rich rules in trusted one, will I be able to reach my server?

I have the following (multiple empty entries are omitted): $ sudo firewall-cmd --list-all-zones block target: %%REJECT%% icmp-block-inversion: no masquerade: no dmz target: default icmp-...
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nftables table and chain priority

I have a problem with my nftables setup. I have two tables, each one has a chain with the same hook but a different name and priority. The tables are in different files which are loaded by an include ...
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nftables: how to use 1 common map (or set) for different but related rules? (dnat + forward)

I am setting up a firewall + NAT using nftables (v0.9.6). The tool provides sets & maps to avoid a lot of rule duplication. I want to use one common data structure (set or map) to configure both ...
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Firewalld forwarded ports are reffusing connection

I have a problem with Firewalld port forwarding. The issue is that forwarded ports are refusing connections or are not responding (TCP flag RSET? on hypervisor where port forwarding is set up) OS: ...
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Set up an IP whitelist programatically on a Linux server

I am fairly new to Linux I have a situation where only registered website members should be allowed to access the server when attempting to login. What I need to do is whitelist an IP automatically ...
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