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I have a linux machine Iam using as a router with multible interfaces and multible internet connection
say eth0--isp1
eth1--isp2
eth2--isp3
the gateway is eth0 throw isp1
and eth3--local1 10.0.0.x
eth4--local2 192.168.1.x
i need local1 ip 192.168.1.10 to go throw isp3, eth2
thanks
You need to use policy routing for this. You create a new routing table and use it when the source IP is 192.168.1.10.
ip route add ... table $TABLENUM # your usual routes, for the new table
...
ip route add default via $ISP3 table $TABLENUM # gateway for the new table
ip rule add from 192.168.1.10/32 lookup $TABLENUM # use the new table for this IP
ip rule add to 192.168.1.10/32 lookup $TABLENUM # make it symmetric, for clarity
Try route add 192.168.1.0 netmask 255.255.255.0 dev eth4--local, on the assumption these are locally-connected networks. If not, you will need to specify a gateway machine to route the packets through also. Truthfully your question is malformed (and probably belongs on serverfault). If you already have addresses on those networks, these routes should already exist. If you do not, your problem is likely more complicated than you think it is.
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When I type a domain URL in the browser (or send a ping or write code that fetches a particular IP) the browser gets the associated IP address based on DNS lookup in a distributed database system - the DNS name servers.
But once the IP is obtained - how does the browser know how to go to the particular computer that this IP represents?
import urllib.request
nf = urllib.request.urlopen("http://192.168.1.2")
The operating system will compare the target IP address with its own IP address. If both addresses are part of the same network, the OS will issue an ARP request to obtain the physical address (the MAC) of the target interface.
If both IP addresses are not part of the same network, the OS will forward the traffic to the gateway responsible for the subnet that is addressed. If it has no such a route, the OS will forward the traffic to the default gateway.
From there the game starts anew.
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I want to set up a reverse proxy in my home network. The idea is to route traffic to correct port number based on subdomain in the request URL.
Example: I'm setting two subdomain A records on my domain: nas.mydomain.tld and wiki.mydomain.tld. Both A records point to my dedicated IP address at home. I want a reverse proxy that routes:
nas.mydomain.tld => 192.168.2.2:5001
wiki.mydomain.tld => 192.168.2.2:8090
Can this be done in e.g. my ASUS RT-AC55U router, or can I route all traffic to my file server and have a reverse proxy there route the traffic to correct IP addresses and ports?
From what I found out, the problem lies in that the functionality I want (multiple types of content retrieved from the same IP and port) cannot be done without some kind of middle-man; a reverse proxy server that fetches the content based on the URL and relays it.
Asus router: My ASUS RT-AC55U router doesn't have a reverse proxy server, at least not with standard firmware. I haven't researched if some unofficial kind of firmware contains a reverse proxy server for doing this. So the only option is to use a NAT record to route port 80 to a specific port. The downside is that it only supports one web service on the IP address.
Web hotel: Creating a rewrite in a .htaccess file on the web hotel of a registrar, but it will only redirect and not rewrite/mask URL. Otherwise, the registrar would need a reverse-proxy server to fetch the content from the web services to relay it. I don't think my current registrar supports this, and I can understand if they don't want to do it from a security standpoint.
Apache reverse proxy server: Apache supports this using the mod_proxy module and an entry in the conf file. More info on it here: https://httpd.apache.org/docs/2.4/vhosts/examples.html#proxy
CCProxy: CCProxy is definitely the easiest solution that I've found so far. It's a simple GUI application where you can add URL's, host names/IP addresses and ports, and the application takes care of the rest. Also has a very nice graphical representation of usage/bandwidth, and a graphical log of ongoing sessions. More info here: http://www.youngzsoft.net/ccproxy/
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Thanks you for your time.
I have just set up a Postfix mail server which is running as MTA in one of my aws instances. I can successfully connect to the localhost through 'telnet localhost 25', and I can send emails to both external and internal email accounts when connected on localhost, however whenever I try to connect through 'telnet zwitch.it 25' or 'telnet mail.zwitch.it 25' I get a connection timeout.
I have set up all my records, including the MX record and the SPF record with the values "v=spf1 include:amazonses.com include:zwitch.it -all" and "spf2.0/pra include:amazonses.com include:zwitch.it ~all".
I really cannot find what is the problem here, if there is a firewall, or if the port is blocked, or maybe something is wrong with my postfix configuration... I would really appreciate if you could help me.
To set up my postfix mail server I followed the instructions at http://flurdy.com/docs/postfix/ where it mentions the installation of a simple postfix server.
I thank you in advance for the help.
EDIT:
Thanks to the answer below the problem was fixed. I only had to go on my aws security groups and add SMTP to the list!
It's one of three things:
1.) You need to edit your security group in AWS to allow port 25 from all external IP addresses.
2.) Your DNS entries for mail.zwitch.it do not point to the external IP address of the AWS instance.
3.) You don't have a static IP (elastic) address configured for the instance.
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Can I specify DNS servers for multiple domains.
For example there are 3 domains for which I know the DNS server which would resolve the domain name, so can I specify something like
b.com (domain)
u1.x1.y1.z1 (DNS server IP address which would resolve b.com)
l.m.n.o (default DNS server used if above DNS server unavailable)
c.com (domain)
u2.x2.y2.z2 (DNS server IP address which would resolve c.com)
l.m.n.o (default DNS server used if above DNS server unavailable)
d.com (domain)
u3.x3.y3.z3 (DNS server IP address which would resolve d.com)
l.m.n.o (default DNS server used if above DNS server unavailable)
please refer https://github.com/whitekid/dnspost
this provide max osx's resolver functionality.
Will following help. In /etc/resolv.conf I will specify,
search b.com
nameserver u1.x1.y1.z1
search c.com
nameserver u2.x2.y2.z2
search d.com
nameserver u3.x3.y3.z3
For d.com, NS u3.x3.y3.z3 will be used (other NS's i.e. u1.x1.y1.z1 and u2.x2.y2.z2 will not be tried for d.com)?
If input domain does not match any of the above given domains then local nameserver will be used?
Also local nameserver will be used if above nameservers are not available or respond with NO?
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in Security+ book, it has been told that DoS attack can be undetectable and an attacker can use an invalid IP address.
what did it mean by Invalid IP address? is it a zombie IP? how can we face with that?
It means spoofing. Spoofing means sending a packet with a source IP that doesn't belong to you.
It's simple, really. The attacker sends a constant stream of packets to the victim and populates ip.src with 127.0.0.1 or 74.125.39.105 or something like that. It does this to hide his identity. If he didn't, you could go to his ISP "Hey, this guy is DoS'ing me! Shut him down".
You must understand that when a packet leaves a host there are not magic rules that ensure it's correct. Most serious operating systems that support IP allow you to send whatever you want in an IP packet.
The attacker can send a packet to the target and spoof the sender IP address. This means he can use any IP address he wants. So the IP address is not really invalid, only there may not be a host connected to the IP address.