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Old 30th August 2009
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Default VPN setup suggestions needed

I am working for a small non-profit that is moving from one facility to three. They will be located within a block of each other and will all use the same ISP with 40Mb/10Mb FiOS connections each and static IP's. I currently have an OpenBSD 4.3 gateway/firewall in place (lets call this home) and plan on using two WRT54GL routers running the DD-WRT VPN firmware at the remote sites. The thought was that I could run OpenVPN in bridged mode (tap) connecting the two very inexpensive Linksys routers to the existing firewall. This would create a simple extension of the home network to the remote locations, if my understanding is correct.

I have the two routers flashed with DD-WRT and OpenVPN 2.1 RC19 (from source) installed on the firewall. This is a small office running XP and Vista on a Windows 2008 AD domain totaling less than 20 computers with one remote site having two computers and the other five or so. I'm in need of some OpenVPN/OpenBSD help here, but before I lose hours of my life going in the wrong direction I would like to ask if this seems like the best approach?
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Old 30th August 2009
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If it were me, I'd just use OpenBSD with IPSec at all three locations, instead of SOHO routers at the remote sites. I say that primarily because I've used both OpenVPN and IPSec with OpenBSD, and the latter is much, much easier to configure and use.

OpenVPN has its advantages, but I don't see any in this particular situation unless DD-WRT is required.
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Old 31st August 2009
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Quote:
Originally Posted by jggimi View Post
If it were me, I'd just use OpenBSD with IPSec at all three locations, instead of SOHO routers at the remote sites.
This isn't totally out of the question, except the routers are pre-existing (but available for re-provisioning) and I don't have any spare computers to run OpenBSD. I could get some used, but it will still cost probably $300 or more in hardware after purchasing the 2nd NIC's and new hard drives. I was just trying to save money.
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Old 31st August 2009
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Quote:
Originally Posted by mikesg View Post
...The thought was that I could run OpenVPN in bridged mode (tap) connecting the two very inexpensive Linksys routers to the existing firewall.
First, let me say that I am a fan of DD-WRT and OpenVPN. That said, the "very inexpensive Linksys routers" may not drive the 40Mb/10Mb FiOS links anywhere near saturation.

The Linksys' switch ports (switch port to switch port) will, but then you're not routing or VPN'ing. The WAN port may not, especially with openVPN encrypt/decrypt running.

/S
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Old 31st August 2009
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A citation in support of s2scott's comment:

From Performance Analysis of OpenVPN on a Consumer Grade Router, http://www.cse.wustl.edu/~jain/cse567-08/ftp/ovpn.pdf:
Quote:
"The performance of OpenVPN depends on the router hardware, and the configuration parameters. The throughput was found to be limited by the router CPU, and is not sufficient for fast connections such as 10/100 Mbps LANs."
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Old 1st September 2009
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If I interpreted correctly, it seems my desired configuration above would be summarized by this statement from the study:
Quote:
For a configuration using the TAP interface with bridging, UDP transport protocol, AES256 cipher, and no compression, the throughput was 3.64 Mbps
Less than 4Mbps doesn't leave me feeling well. I will look into the IPSec method and possibly the ssh -w method I saw mentioned in another thread. Thanks both of you for the links and input.
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Old 1st September 2009
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Just FYI regarding cipher and key sizes.

The computational work units needed to crack the AES block cipher strength at 128 is the same computational work units needed to crack a DH key at 3072 bits.

DH 1024 is no longer sufficient. DH 2048 is becoming insufficient.

AES128 is MORE then sufficient for a real-time stream, especially if you cipher block chain as openVPN does by default, and is out of reach for a fair while still given today's available processing power, including grid computing and Moore's Law factored in. DH3072 is out of reach for quite a while.

I love Admin's who use a weak 512 or 1024 DH key to secure an overly-strong AES256 cipher key.

Recommend you dial down the AES and dial up the periodic-event DH strengths. It'll help with your throughput.

/S
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Last edited by s2scott; 1st September 2009 at 04:11 AM.
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Old 1st September 2009
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Oh, if the AES128 cipher operations uses a pre-shared key instead of a DH key exchange, then a pre-shared key of 63 characters of an "alphabet" of [0-9][a-z][A-Z][the other printable chars] is way out of reach.

Twelve (12) or fewer characters is vulnerable. Sixteen is considered "safe" minimum at today's processing power.

BTW, this is true for all the WPA and WPA2 wireless access points out there.

So amp-up the "password"/"key" lengths.

https://www.grc.com/passwords.htm is my favorite random key generator site. Notice it's SSL only access.

/S
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Old 4th September 2009
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Is there a good modern FAQ/HowTo for IPSec VPN's on OpenBSD? I've been reading this, but it's old, and many I have found are far older.

securityfocus.com/infocus/1859
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