iptables is the userspace command line program used to configure the Linux 2.4.x and 2.6.x IPv4 packet filtering ruleset. It is targeted towards system administrators. Please, when asking a question about iptables, add the output from the following command: iptables -L -v -n

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Get Original Destination Port From iptables

I would like to create a local server that acts as a proxy for all trafic, but how would I determan the original ports when using iptables to rederect the network traffic. I need this for when the ...
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50 views

Fail to redirect requests to specific url to localhost

I have a server that listens on http://localhost:3000 and I want to forward all requests to http://api.lingualeo.com/addword from Chrome extension (some JSON data) to http://localhost:3000. What I ...
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208 views

Linux ipv6 forwarding

Situation I know how to do ipv4 forwarding, and expected ipv6 forwarding to work pretty much the same way. So I configured a VirtualBox host with the network address configured from my ISP. Right ...
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806 views

How to configure iptables when running Docker

I have a difficult situation here, i have setup many containers on my docker host, running different applications like mailserver, databases, redis, and certain html applications using other ...
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69 views

iptables foward to multiple interfaces with NAT

I want to use iptables for provide NAT translation and forward the packets out a different interface. The network set-up is as follows: Alias: eth0:220 with IP address 10.1.1.220 / 255.255.252.0 ...
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438 views

Virtual IP Pool for NAT with StrongSwan VPN

I'm trying to wrap my head around a site-to-site VPN configuration using StrongSwan that will allow remote sites to connect to our AWS VPC. The catch is, the remote gateways will potentially be using ...
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183 views

How to block hping3 SYN ACK efficiently with iptables?

Actually I'm trying to execute a SYN TCP flood on my Debian web server with nginx and, by executing tcpdump "tcp[tcpflags] & (tcp-syn) != 0" while flooding, I see all packets coming. I already ...
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782 views

Squid intercept proxy stuck with forwarding loop

I'm trying to set up a debugging proxy using Squid, mainly to test our own client communications library for various proxy types (one possibility with our client, is to connect to an external ...
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18 views

Troubles with subnets and redirections

What I want to create is 2 subnets that communicate each other through a gateway. Here is my gateway: wlan0 Link encap:Ethernet IndirizzoHW c4:46:19:69:b7:a5 indirizzo ...
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4k views

squid transparent proxy for https / ssl trafic

I am trying to configure squid as transparent proxy , I followed below steps to configure Downloaded squid3.5 from the website, As squid3.1 will not support for ssl bump ./configure ...
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89 views

iptables keeps using old nat rules

I use iptables snat on my gateway to change local source ip addresses to external. The trouble is that after I change the rules (or even if I flush iptables nat table) gateway keeps using the old rule ...
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413 views

Docker open ports in iptables (rabbitmq)

I'm having a docker image based on rabbitmq. Nothing in my Dockerfile specifies anything about ports. I bind the usual rabbitmq ports (5671, 5672 and 15672) to my custom ports by running my instance ...
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139 views

Connect AWS and Azure via OpenVPN

I am trying to connect two networks (AWS and Azure) together via OpenVPN. I am aware of other implementations (OpenSwan+Azure GW etc.) but I need maximal portability as I will be expanding this to ...
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261 views

How to use iptables or IFB to mark incoming traffic by device?

I'm trying to use iptables to mark incoming packets based on the device where those packets arrived (rather than their originating IP address or port etc), but haven't found a way of getting this to ...
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134 views

OpenVZ : live migration fails

I can't launch live migration of OpenVZ container between two proxmox nodes... Feb 05 03:30:27 starting migration of CT 102 to node 'madrid' (xx.xx.xx.xx) Feb 05 03:30:27 container is running - using ...
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58 views

Clone and then route SNMP traps to new destination

We have 2 SNMP trap servers 10.0.0.1 and 10.0.0.2 which are the SNMP trap servers for close to 500 devices that we monitor.In all these 500 devices,10.0.0.1 and 10.0.0.2 are configured as the trap ...
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116 views

Redirect incoming WAN connection to other WAN host with iptables

I have router with Linux. I want to redirect incoming WAN connections with specified port to some other WAN host:port. I've tryed do this standard way: iptables -t nat -A PREROUTING -p tcp --dport ...
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127 views

iptables traffic after forwarding

I have 2 servers Server A and Server B ServerA = 1.1.1.1 ServerB = 2.2.2.2 I am using ip-tables to send all traffic on port 80 to Server B on Server (A) 1.1.1.1 i have done iptables -t nat -A ...
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357 views

Does netfilter reassemble IP fragments when packet is forwarded?

IP datagram should be reassemble in the termination of the path because the fragments may arrive from different paths. I think Netfilter need to reassemble a IP datagram to inspect the whole payload ...
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37 views

How can I proxy requests to a specific IP to a different IP on OS X?

On OS X how can I setup a route so that when I make a request to 10.0.0.1 it is redirected to localhost? Right now I can do curl localhost:3000 and get back a blob of HTML from my running node web ...
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78 views

Strange entries in Squid3 access.log

My WiFi network for guests is transparently proxied by Squid3. There's now a girl from Indonesia with her Samsung GT-B5330 running Android 4.0.4, who gets blocked by "The requested URL could not be ...
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165 views

linux not replying to an arp request

I am running linux 3.14 on a system with 2 interfaces. on the first interface, i can access our local network. on the second interface, arp packets come in but linux doesn't send out reply. is it ...
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228 views

amazon ec2 instance going to a remote ip using openswan tunnel is up but no traffic being established on the remote ip

I having establishing a vpn tunnel to a remote peer/public ip using amazon ec2 openswan. The tunnel is up but no traffic has been seen on our side or the remote side? Is there I been missing? Please ...
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116 views

Dovecot/Postfix mail server replies to [SYN] with [RST, ACK] when user attempts to connect (POP3). Likely iptables?

Currently I am trying to trouble shoot an e-mail server that will allow users to send e-mail, but not log in to the server (POP3) or receive e-mail using their Outlook clients. Previously this was ...
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281 views

Forward single port between subnets on dd-wrt router

I have a DD-WRT router with two subnets, 192.168.0.0/24 and 192.168.8.0/24. The latter is used for a 'guest' WiFi network. Traffic between subnets is filtered using iptables. What I would like to ...
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171 views

What does Nginx Proxy Filter in Fail2ban really do?

What does Nginx Proxy Filter in Fail2ban really do? I am currently setting up Fail2Ban for Nginx. Almost everywhere I've read, they all have included a setting for [nginx-proxy] proxy filter. From ...
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60 views

NAT for IPSEC access?

Please help to understand if the following configuration can be created. I have IPSEC connection with my customer. It is site2site vpn between customer network and my network 10.102.103.0/28. This ...
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277 views

shorewall can'T start: UNTRACKED state requires Raw Table in your kernel and iptables

I'm trying setting up my firewall and installed and configured shorewall. Unfortunately I tried to directly configure iptables first, but this didn't work. When I start shorewall, I get this messages ...
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384 views

Shorewall: DNAT to IPSEC tunnel zone not routing correctly

I have a ipsec tunnel working that gives access to a 192.168.4.0/24 lan. It is working fine and I can access hosts on the other side without problem: # from fw and lan hosts: # ping 192.168.4.44 PING ...
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56 views

Why do some outgoing IP traffic not contain UID information?

I am doing egress logging on my server using IPTABLES with the following line which is supposed to provide UID information on all traffic that is logged: -A OUTPUT -j LOG --log-prefix "IPTABLES(O): " ...
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77 views

Automatically add rules to iptables when an user logs in or logs out with ssh?

I'm looking for a solution to automatically add couple of rules to iptables when an user logs in and remove those rules when it logs out. I'd like to get somehow get the ip address of the user from ...
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589 views

Client successfully connects to OpenVPN server but with no internet access over the VPN

I'm trying to setup OpenVPN with static key authentication(instead of TLS) on TCP port 443; but the client cannot access the internet over the VPN after connecting to the server. Here's my current ...
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4k views

Transparent Proxy squid TCP_MISS/503 Error in all pages

I m trying to make a squid proxy server with to work as a transparent proxy server, and i m facing some issues that i m unable to figure out the reasons. The setup i m using is several VLAN's with ...
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2k views

TPROXY Not working with HAProxy, Ubuntu 14.04

I'm trying to use HAProxy as a fully transparent proxy using TPROXY in Ubuntu 14.04. HAProxy will be setup on the first server with eth0 111.111.250.250 and eth1 10.111.128.134. The single balanced ...
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122 views

Policy routing local user's traffic down a tunnel

I've got a Linux based Firewall/Router running iptables and SNAT for traffic passing through it to the Internet via a single uplink - This is working fine. There is also a small number of applications ...
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127 views

`ufw insert 1 deny to any` not working

ufw insert 1 deny to any ufw enable ufw status Status output: Status: active Logging: on (high) Default: deny (incoming), allow (outgoing), disabled (routed) New profiles: skip To ...
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49 views

EC2 instance won't allow pinging

Ive got an EC2 instance with an iptables config as follows: *filter :INPUT ACCEPT [121:8012] :FORWARD ACCEPT [0:0] :OUTPUT ACCEPT [64:6240] -A INPUT -p icmp --icmp-type echo-request -j ACCEPT -A ...
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203 views

Iptables multiport and source ip

I have a rule which does not seem to allow traffic as expected -A INPUT -p tcp -m state --state NEW -m multiport -s x.x.x.x -d y.y.y.y --dports 38000:38100 -j ACCEPT If I remove the -s argument ...
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0answers
57 views

How to test if packet has been tagged with classid

I'm trying to troubleshoot an issue I'm having related to IFB Mirroring which I'm attempting to deploy based on this question: Tc: ingress policing and ifb mirroring My theory is that since the ...
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0answers
327 views

Firewall rejecting UDP “connections”?

I have a server that is aggregating logs from various other servers. It mostly works great, however from time-to-time (right after a reboot, but not all reboots) it will decide that various UDP ...
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122 views

Is it possible to incorporate ndpi with iptables nfqueue?

I would like to know if it is possible to mark traffic with ndpi (ntop.org) classification engine with iptables nfqueue? Is there any example code out there? Thanks for helping.
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129 views

Can I use iptables to rate limit an ipset?

Is it possible to use iptable tables to rate limit an ipset ? I know you can use ipset to create a block list named blacklist i.e. ipset create blacklist hash:ip iptables -I INPUT -m set ...
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51 views

ospf hello not forwarded

I am trying to change the destination ip of ospf hello packet (224.0.0.5) to link local address using iptables rule (DNAT) . It does not seem to work. A similar rule for unicast packet (BGP control) ...
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129 views

Openstack instances, routing, packets not delivered for SPECIFIC services

I am taking over management of an existing openstack system at work and I have only a little prior experience with openstack. I have about 8 instances running and all of them appear to function ...
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242 views

Firewall and NAT settings in GSM modem for one server

I have a GSM Modem (PSI-MODEM-GSM/ETH) in field with one device behind, acting as a server. The situation is as follows: "PC" | \_________Dynamic IP: 10.103.153.122 | ...
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317 views

Routing LDAP traffic from Application server to Proxy to internet

I've included a drawing so you get an idea how it would work. (Red = LDAP connections , Blue = HTTP / AJP in the backend) Problem: We want to connect our customer application server to an LDAP of ...
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497 views

How to configure nDPI for iptables

I am new to nDPI, I have installed nDPI but when I add rules like; iptables -I OUTPUT -m ndpi --http -j REJECT it shows error iptables v1.4.7: Couldn't load match ...
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462 views

Confirm IPTables firewall settings for NFS v4 server?

This question has been asked here before but has conflicting and possibly outdated answers. It seems to depend on OS, version of OS, and version of NFS. On a CentOS 6.5 server, the default rules are ...
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151 views

LXC and proxying port 22 (ssh)

I have installed LXC on my Ubuntu 12.04 server and have created a couple of containers. I have only 1 external IP address, thus I am using nginx on my host machine to proxy HTTP requests from certain ...
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390 views

iptables - hashlimits, why it calculate all to seconds

I've tried to set 'synflood' limits with hashlimits, those are my snippet of rules: iptables -A SYNFLOOD_CHECK -p tcp --syn -m hashlimit --hashlimit-above 10/s --hashlimit-burst 6 \ ...