Networking :: Iptables Routing Packets On Same Sub-network
Feb 17, 2010
I am running into trouble while trying to set-up a iptables routing policy. I have two machines on the same sub-network (xxx.xxx.153.0). One of the machines is used as a default gw for the other (xxx.xxx.153.250 is a gateway for xxx.xxx.153.142 and xxx.xxx.153.254 is a gw for xxx.xxx.153.250). There is no explanation for why the xxx.xxx.153.250 is in the middle -- xxx.xxx.153.142 can go straight to xxx.xxx.153.254, but is is like that for now.I am trying to find an iptable rule to be executed on the xxx.xxx.153.250 machine to route the packets.
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Sep 6, 2010
My setup is...I have a wireless access point using laptop as a gateway. The AP is also connected to a switch as is the laptop. So the laptop has two interfaces one wireless and one wired. A third device is using the AP to connect to a server on the internet. The AP sends the packets to my laptop where they are dropped. I've been looking for a solution to this problem without success. Basically is there a way for my laptop to forward all packets it sees from a certain IP address to whatever destination address they have?To clarify, my laptop is just the gateway of the AP and none of the packets are addressed to it at all, it just picks them up using a sniffer or similar tool.
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Aug 9, 2010
My requirement was to direct certain traffic from various ports down different Internet connections. Basically, for locally generated packets, the OUTPUT chain in the mangle tables is used. You can MARK packets in this chain for ip rule processing.Now the "clear as mud" part. There must be a valid routing decision made without the fwmark, selecting the right source address, even if the gateway ip is invalid.
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May 10, 2011
I have a router/modem linux box, connection to DSL through PPP.I also use an OpenVPN service, to which this box connects.My problem is that the speed cap of the VPN is just half that of the DSL connection. I don't need it for internet browsing. Is there a way I can route all the http traffic coming from the client computers (or all of the traffic will do too) through the normal connection?As of now I can only route all traffic either on VPN or normal PPP
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Feb 24, 2011
I am establishing a VPN connection with a Cisco VPN server, but only want outgoing connections to a certain set of IP addresses to actually go through the VPN. I tried something like this:
Code:
sudo iptables -A OUTPUT -t mangle -p tcp -d 111.222.0.0/16 -j ROUTE --oif tun0
but keep getting
[code]...
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Dec 6, 2010
I've been trying to redirect all outgoing packets (destined for a specified ip address) from my slack box back to itself. I thought this could be done with iptables, but if I fire up wireshark I can clearly see that the packets are getting out to the real server and I'm getting responses from it.
So here's what I tried:
All looks good and fine, and then I even try to visit 194.28.157.42 with firefox (by the way I am running a webserver, that is set to show a page when you visit 127.0.0.1) and I get an error page that reads: 502 Bad Gateway.
I ignored this message to see what the program I'm trying to interrupt does, and when I start wireshark and then start the program that is using that website, I can clearly see that the packets make it to the real 194.28.157.42 and get back responses.
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Aug 20, 2010
I have an Untangle Box - which for those that don't know is a modified Debian Lenny used as a router, proxy, filter and much more - It has three physical interfaces on it eht0 (incoming traffic), eth1 (Outgoing to LAN after traffic filtered), and eth2 (Called a DMZ NIC, as Untangle can be used as a router). There is also a tun0 interface setup by Untangle for VPN (Not using the Openvpn in Untangle because I need bridged a bridged VPN and this is not an option in Untangles offering), a br0.eth setup by untangle to bridge eth0 and eth1 for traffic flow through as it is inline from router to switch and not acting as the router itself, and a br0 interface that I have setup by bridge script bridging eth2 and tap0 to run OpenVPN as a bridged VPN.
The routes on the machine are as follow:
Code:
untangle:~# route
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
192.168.100.0 * 255.255.255.0 U 0 0 0 br.eth0
192.168.1.0 * 255.255.255.0 U 0 0 0 br0
192.0.2.0 * 255.255.255.0 U 0 0 0 dummy0
192.0.2.0 * 255.255.255.0 U 0 0 0 utun
untangle:~#
I don't see a default route listed here, however, I do have Internet connectivity on the Untangle box itself. I also know that by script to bridge the tap0 and eth2 interfaces adds a default route through the gateway on the network that eth2 is connected to. So the lack of a default route is somewhat puzzling to me, I do have the gateway set through the web based admin interface Untangle offers.
The iptables rules are as follow:
Code:
untangle:~# iptables --list-rules
-P INPUT ACCEPT
-P FORWARD ACCEPT
-P OUTPUT ACCEPT
-N alpaca-firewall .....
There was an addition output rule in the alpaca-nat-firewall rule that said DROP outgoing interface eth2, I removed that rule with no change. I can ping out from the Untangle server to the eth2 LAN, I can access resources in the eth2 subnet. But I cannot get any reply from the server from anything either in that subnet or not. If I run iftop I can see the incoming traffic form my ping but the Server sends out no reply. I think this is a firewall issue. I can access the server by connecting to the IP assigned to the eth0/br0.eth interface which is in my main LAN. I am also attaching a crude diagram of the previous setup and the new setup (Previous setup used a different server for my bridged VPN).
Is there a rule I can add to ensure that traffic coming in on an interface goes out the same interface? Do I have a rule blocking incoming traffic to eth2/br0? Do I have one blocking sending out on eth2/br0? Do I have a default rule that is killing the traffic on eth2/br0 and I need to add an accept rule for traffic coming in on eth2/br0? I tried adding an accept rule for traffic coming in on br0, but it didn't work. I tried an output rule, but that didn't work, but I may have been bungling these rules as I do not fully understand the syntax and function and body of an iptables rule. The exact original iptables information before I modified anything can be viewed at [URL].
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Mar 16, 2011
I had been running my SMTP server with WINE, as the SMTP server software is a Windows-based program (MERCURY), but I cracked the shits with WINE and removed it. Now I am running my SMTP server in a Windows virtual machine.This virtual machine has a different IP address from my host machine, so what I need is for my computer (the host) to redirect incoming traffic on port 25 to the virtual machine at 192.168.56.101 on port 2525.Can someone please help me with it? I think its done with iptables.
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Mar 13, 2011
I'm trying to configure NFS sharing behind a firewall, I got it to work and all but I was caught by something that (to me anyways) seems odd.I've been able to mount the export on another computer and am transferring files over as we speak, but I'm just interested in knowing why the RELATED,ESTABLISHED rule seems to be catching almost all the traffic coming from the other node. Any ideas? Should I be concerned that my firewall isn't protecting anything or something?
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Sep 10, 2010
I have a very weird case in my firewall.I have an asterisk server and some phones and between them there is a linux firewall based on iptables.With basic rules on iptables everything works ok, but when I put a single nat rule (no matter what rule I use) some packets from some phones misteriously disappear from interfase to interfase.
Clearer:The firewall has two interfases: eth0 (pointing to phones) and eth2 (pointing to asterisk).One problematic phone is 192.168.3.242, so I use tcpdump this way.
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Jun 26, 2009
if am using --log-prefix "BANDWIDTH_OUT:" --log-level 7 to capture packets, I think is there a way to view these?
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Sep 23, 2010
I'm trying to configure Iptables and I just want to block everything but http/https. However, my connection is pppoe, so I have the ppp0 interface. Pretty much every Iptables tutorial that I found don't teach how to deal with this kind of setup. I'm forwarding the ppp0 to eth0 and I could configure the input rules and they're working. After this, I need to configure the output but nothing seems to work.
The current working rules are:
Code:
Chain INPUT (policy ACCEPT 7858 packets, 5792K bytes)
pkts bytes target prot opt in out source destination
299 201K ACCEPT all -- any any anywhere anywhere state RELATED,ESTABLISHED
0 0 ACCEPT tcp -- any any anywhere anywhere tcp dpt:www
0 0 ACCEPT tcp -- any any anywhere anywhere tcp dpt:https
11 820 DROP all -- any any anywhere anywhere
Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
0 0 ACCEPT all -- eth0 ppp0 anywhere anywhere
0 0 ACCEPT all -- ppp0 eth0 anywhere anywhere state RELATED,ESTABLISHED
Chain OUTPUT (policy ACCEPT 10791 packets, 1951K bytes)
pkts bytes target prot opt in out source destination
I don't understand what those "state RELATED,ESTABLISHED" rules do. Also, I don't know if this rules are secure, because i'm very confused about the ppp0/eth0 interfaces.
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Jul 2, 2010
I two servers set up: 192.168.1.150 and 192.168.1.160 Initially, I want all traffic to be served by server 150. So for this purpose I am leaving the IPTables on .150 empty. At a point in time, I want to forward all incoming traffic to be served by .160 instead. I have accomplished this using these commands (on .150):
iptables -t nat -A PREROUTING -j DNAT --to 192.168.1.160
iptables -t nat -I POSTROUTING -j MASQUERADE
My problem is that if I have an open SSH connection to .150 (prior to adding the rules), the packets are still handled by .150 after adding the rules.. e.g. my SSH session stays active. I want these packets to be forwarded to .160, which would effectively disconnect the SSH session. I do not want the packets flat out dropped, I just want them forwarded on in whatever state they are in. If I try a new SSH session, it is properly forwarded to .160
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Mar 22, 2010
I am trying to do something outlandish with iptables (or so I think!).I have a source sending udp packets to a destination (say dst11). Using port mirroring I am able to get all these packets to a different machine (say dst22). I am able to see these packets on dst22 interface using tcpdump.I want to analyze the packets on dst22. So what I do is put dst22 interface in promiscuous mode (using ifconfig eth0 promisc). This in theory should get the packet through the MAC layer. Now using iptables I am trying to DNAT the packets in nat prerouting to change the packets destination IP to dst22's interface and change the destination port.
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Apr 13, 2010
I'm running Ubuntu 9.10 server at home on VMware Workstation 7. I have two NIC's configured, one NIC is setup to have a direct connection to the network "Bridged", another NIC is setup to have a private network connection on VMnet1.
Network card 1 - 192.168.1.160 (Bridged)
Network card 2 - 10.1.1.1 (Internal access only)
So when I try to access the Internet, I can not go out on the NIC 1. If I try to ping google.com I get a return from 10.1.1.1 "no reply". But I know that NIC 2 is working, because I can ping 192.168.1.160 from the workstation I'm running on.
So I think that my routing is sending traffic out to the wrong NIC, but not sure if this is a metric in the iptables or another place?
The reason for two NICS is to simulate a DMZ where the server will be running Squid, to test proxy from another workstation on the 10.1.1.X subnet.
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Mar 24, 2010
Is there any possible way I could add loose/strict source routing for traffic originating from a host ? I mean to add certain hops I want my packet to pass.With iproute2 or maybe iptables ?
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Aug 26, 2010
I'd like to (if it's possible, of course) to redirect the packets originated within a linux box, and I've been tryin' to do it through the OUTPUT chain in nat table:
Code:
iptables -t nat -A OUTPUT -p tcp -d 192.168.0.74 --dport 80 -j DNAT --to-destination 192.168.0.17:80
The policy for the rest is ACCEPT.This redirection didn't work this way. If I do lynx http://192.168.0.74:80 I reach 192.168.0.74 host, so there is no redirection.Could I achieve what I'm needing through with IPTABLES' OUTPUT chain (in nat table)?
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May 8, 2011
I have 3 network interfaces on my Linux Router :
Interface - Gateway - Type
Code:
br0 - 192.168.0.1 - Internet
eth2 - 192.168.1.1 - LAN
tun0 - 10.0.0.2 - VPN (via br0)
What I'd like to do is to route all TCP packets coming from eth2 to tun0 where a VPN client is running on 10.0.0.2. If I delete all default routes and if I add a new route to tun0 like :
Code:
route del default
route add default gw 10.0.0.2
Everything is fine, and everyone on eth2 can reach the Internet using the VPN access. Now the problem is that my VPN client does not allow any other protocols other than TCP. And I also want to allow VPN access only to eth2, no other LAN nor the router itself. use iptables to filter any TCP packets and mark them, so they can be sent to tun0, while any other packets can reach the Internet via br0 (192.168.0.1). I found on the Internet that we can mark packets before they get routed. Using the following commands :
Code:
iptables -t mangle -A PREROUTING -j MARK --set-mark 85 -i eth2 -p tcp --dport 80
ip route add table 300 default via 10.0.0.2 dev tun0
ip rule add fwmark 0x55 table 300
First of all, --dport 80 never work... :/ I wanted to filter TCP 80 packets coming from eth2, but none of them seems to be HTTP packets... oO (very strange...). Nevermind, I decided to forget about the --dport option. I use the "iptables -L -v -t mangle" command to see how many packets are marked, and it is working fine, all TCP packets coming from eth2 are marked. Now the problem is that none of them are routed to tun0 they are all respecting the "route -n" rules... and not the "table 300" rule I have created.
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Apr 4, 2011
I'm trying to use iptables in order to forward all the incoming packets for port 5555 to port 5556 on the same server (192.168.2.101).
I wrote the following commands:
iptables -A PREROUTING -t nat -i any -p tcp --dport 5555 -j DNAT --to 192.168.2.101:5556
iptables -A FORWARD -p tcp -m state --state NEW -d 192.168.2.101 --dport 5556 -j ACCEPT
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Mar 31, 2009
I have two networks. One of them is wired, the other is wireless. The wired has an internet connection and a few other computers connected to it. The wireless network has a few hosts connected to it too, but it has no internet connection. What I've been trying, fruitlessly, to do, is make all connections that are bound to the internet, or my wired network, be routed that way, and all the connections to the hosts of the wireless network go that way.
Here's the setup..
Wired:
192.168.1.0/24 Gateway = 192.168.1.1
Route internet through here
Wireless
192.168.2.0/24 Gateway = 192.168.2.1
If my computer sends a packet to the internet, it should be routed through 192.168.1.1 If I send a packet to one of the local hosts of the wireless network, it should be routed through 192.168.2.1. Here's the routing table I've set up(This is one of many configurations I've tried)
Code:
$ ip route show
192.168.2.1 dev wlan0 scope link
192.168.2.0/24 via 192.168.2.1 dev wlan0 src 192.168.2.4
[code]....
With this, and everything else, I get destination host unreachable when pinging. The strange thing is that, if I unplug my eth cable, reboot and connect to the wireless network, everything is fine and I can access the router and the others. I'm trying to improve my networking skills, as I've had this of setting up a small linux box as a router for quite some time, for the fun of it, but I need to get routing under control before I go ruin my network.
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Nov 28, 2010
At every site i have two provider vsat and wireless connection.I have a linux machine and wanna setup act router for every site.
SITE 1 :
vsat : gw 10.23.128.1
wireless : gw 192.168.100.1
[code].....
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Feb 1, 2010
My hardware has two interfaces: a) ethernet - eth0 b) WirelessLAN - eth1.After power on, eth1 gets associated to WirelessLAN access point.
The ethernet interface of Hadrware and test PC is directly connected to Wireless LAN access point through ethernet cable. Hardware is associated to Wireless LAN access point through eth1 interface.Now, when ethernet cable is connected to hardware, I can ping 192.168.254.254 from test PC.When I removed ethernet cable from hardware, I cannot ping 192.168.254.253 from test PC.I think access point should forward the incoming packet from test pc to hardware's eth1 interface wirelessely. Where am I wrong? Is it related to Kernel's routing table? If yes, how to detect removal of ethernet cable from hardware and change routing table dynmically?
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Dec 10, 2008
I am not a networking expert by any means (in fact I have never taken a networking course), but I have taken several security courses, and generally we wind up discussing replay attacks. For example, the Needham-Schroeder protocol (using symmetric-key cryptography anyway) is flawed because it allows for replay attacks, and I understand why.
I guess my question is actually how someone would perform a replay attack. I know I can sniff network traffic by downloading wireshark. I also have downloaded winpcap and npg on my WinXP virtual machine. I'm trying to use this guide to help me, but I'm quite lost:[URL]What I did was to post a "link" to my facebook profile and I sniffed the traffic using wireshark. What I would ultimately like to accomplish is to copy that packet out of the wireshark output, and then use a tool like npg to transfer the raw packet back to facebook, which should result in a second, redundant post. I just can't figure out how to do that.
I'm pretty sure this should be possible. Facebook only uses an SSL session for authentication during login. After that, the information is just sent in the clear, so I'm pretty sure this should be possible.Can anyone explain how to do such a thing? It would really help my research paper that I'm working on this semester if you can. As of right now the attack we are trying to demonstrate/defend against is using a Windows VM, which is why I'm using winpcap/npg. The attack is actually possible using just about any OS (depending on the exploit used), but our POC is Windows only at the moment
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Feb 15, 2011
I'm using madwifi linux driver (ath1) in monitor mode to capture some wireless traffic. I can see that all wireless traffic is coming well through the wireless interface (checked using TCPDUMP). What I want to know is how I can forward the captured wireless packets to a different Ethernet interface (e.g. eth2) in the same machine to send those captured packet out to a different computer.
I set 1 for /proc/sys/net/ipv4/ip_forward
for iptables, I tried this rule: iptables -A FORWARD -i ath1 -o eth2 -j ACCEPT
However, I coudn't read any packet from eth2 via TCPDUMP.
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May 24, 2010
I have tried to google it around and couldn't find any good solution for it. What I want is to hook up to the kernel network hooks and for example investigate all of the packets (maybe keep some in the buffer and drop in the kernel so I could send them out lets say 10 minutes later) but from a C / C++ program perspective / level. I know it can be done via iptables but isn't there a way to do it from a program ?? I have found a library called ipq but apparently doesn't work with kernel 2.6.x anymore.
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Apr 6, 2010
I have a firewall, this consists of three NIC's:
Code: eth0[192.168.0.2] eth1[192.168.1.2] and eth2[10.10.165.2]
I am trying to ping eth0 from eth2, but I am not able to succesfully get a response from pinging the device, I am using:
Code: ping 192.168.0.2 -I eth2
I have tried to insert routing data into the routing table, but it still doesn't work
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Jan 21, 2010
I have a program that connects to the internet that I would like to route through one of my secondary network interfaces. I need one specific port routed to eth1 instead of eth0. I believe that I should be using iptables for that, but I don't really know how to do it.
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Aug 26, 2010
I am using Network Manager to connect to a VPN server so that I can access some of the computers on the local network there. When I'm connected, I have two problems: All my internet traffic goes through the VPN. My computer is no longer visible on my local network. I waste a lot of time connecting and disconnecting the VPN. Is there any way I can set up a VPN so that I am still on my local network and only requests to 172.x.x.x go through the VPN. I suspect it can be done with iptables, but all the info about iptables goes WAY over my head.
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Feb 8, 2010
i have a linux server runnig oracle applications. i need to access this server from putty using ssh through internet. i did by registering my static ip with the dnydns.org and i am able to connect to the server. but now there is no security to authenticate any user as any one knowing the password can login to it.
i thought of configuring the firewall of linux server but the client ip`s are not static and they change continiously. so thought of keeping one more pc between the server and the router which will do the work of authenticating. but i am confuse as how to configure it to allow the packets coming from the internet after authenticating and to by pass the packets generated from internal LAN?
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Jun 2, 2011
I'm trying to drop all packets from the internet that use a fake ip address so they appear to come locally.
Do I need both lines or only the first ?
--append INPUT ! --in-interface lo --source 127.0.0.0/8 --jump DROP
--append INPUT ! --in-interface lo --destination 127.0.0.0/8 --jump DROP
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