LinuxSecurity.com
Share your story
The central voice for Linux and Open Source security news
Home News Topics Advisories HOWTOs Features Newsletters About Register

Welcome!
Sign up!
EnGarde Community
Login
Polls
What is the most important Linux security technology?
 
Advisories
Community
Linux Events
Linux User Groups
Link to Us
Security Center
Book Reviews
Security Dictionary
Security Tips
SELinux
White Papers
Featured Blogs
All About Linux
DanWalsh LiveJournal
Securitydistro
Latest Newsletters
Linux Security Week: April 7th, 2014
Linux Advisory Watch: April 4th, 2014
Subscribe
LinuxSecurity Newsletters
E-mail:
Choose Lists:
About our Newsletters
RSS Feeds
Get the LinuxSecurity news you want faster with RSS
Powered By

  
( IP Aliasing ) - Can IP Masquerade work with only ONE Ethernet network card?

7.28. ( IP Aliasing ) - Can IP Masquerade work with only ONE Ethernet network card?

Yes and no. With the "IP Alias" kernel feature, users can setup multiple aliased interfaces such as eth0:1, eth0:2, etc but its is NOT recommended to use aliased interfaces for IP Masquerading. Why? Providing a secure firewall becomes very difficult with a single NIC card. In addition to this, you will experience an abnormal amount of errors on this link since incoming packets will almost simultaneously be sent out at the same time. Because of all this and NIC cards now costs less than $10, I highly recommend to just get a NIC card for each MASQed network segment.

Users should also understand that IP Masquerading will only work with a physical interface such as eth0, eth1, etc. MASQing out an aliased interface such as "eth0:1, eth1:1, etc" will NOT work. In other words, the following WILL NOT WORK reliably:

  • It is rumored that you can simply use the destination IP address (the IP address associated with the ALIASed interface like eth0:1, etc.) IN PLACE of specifing the interface (eth0:1). This solution is not untested -- please email dranch@trinnet.net if you have any positive or negative results

  • /sbin/ipchains -A forward -i eth0:1 -s 192.168.0.0/24 -j MASQ"

  • /sbin/ipfwadm -F -a m -W eth0:1 -S 192.168.0.0/24 -D 0.0.0.0/0

If you are still interested in using aliased interfaces, you need to enable the "IP Alias" feature in the kernel. You will then need to re-compile and reboot. Once running the new kernel, you need to configure Linux to use the new interface (i.e. eth0:1, etc.). After that, you can treat it as a normal Ethernet interface with some restrictions like the one above.

    
Partner

 

Latest Features
Peter Smith Releases Linux Network Security Online
Securing a Linux Web Server
Password guessing with Medusa 2.0
Password guessing as an attack vector
Squid and Digest Authentication
Squid and Basic Authentication
Demystifying the Chinese Hacking Industry: Earning 6 Million a Night
Free Online security course (LearnSIA) - A Call for Help
What You Need to Know About Linux Rootkits
Review: A Practical Guide to Fedora and Red Hat Enterprise Linux - Fifth Edition
Yesterday's Edition
Heartbleed: Security experts reality-check the 3 most hysterical fears
Open source trounces proprietary software for code defects, Coverity analysis finds
Partner Sponsor

Community | HOWTOs | Blogs | Features | Book Reviews | Networking
 Security Projects |  Latest News |  Newsletters |  SELinux |  Privacy |  Home
 Hardening |   About Us |   Advertise |   Legal Notice |   RSS |   Guardian Digital
(c)Copyright 2014 Guardian Digital, Inc. All rights reserved.