Re: [coLinux-users] Fwd: unable to get slirp (ping) working

[Henry N. <hen...@ar...>]

  Eric S. Johansson wrote:
> On 5/9/2010 9:24 PM, Hari Krishna Dara wrote:
>> I added DNS servers ips from my vpn adapter to the /etc/resolve.conf
>> along with my router's ip. I am able to ping to those name servers
>> when my vpn is up (which BTW, I thought wouldn't work because slirp is
>> not supposed to support ping). I suppose there is nothing that can be
>> done on the windows side? Would adding additional NAMESERVER entries
>> into the /etc/sysconfig/network-scripts/ifcfg-eth0 help (which I am
>> not actually sure is valid).
> I think you're hitting a problem I have hit a few times with open VPN. Forgive
> me if I misinterpret your problem and solving something else entirely.
>
> DNS is built on the assumption that all name servers have the same data.
> unfortunately, when you have a VPN, you no longer have this situation. Each name
> server at the end of a VPN has a different set of names that you Can't access
> via the public Internet.  one would think that the normal round-robin feature of
> most resolvers would help bridge the difference between the two name spaces but
> no, many DNS proxies return the wrong response and prevent the round-robin
> behavior from happening.
>
> This problem gets worse when you have two or three VPNs open at the same time.
> No matter what name server you use, names without on the other VPNs will be
> invisible.  Unfortunately, the only answer seems to be a specialized DNS proxy
> that associates a domain with a name server plus the default of "on the Internet".
>
> I've tried using dnmasq to solve this problem because it has the right
> capabilities but unfortunately, every time DHCP renews lease, the DNS name
> server entry is overridden and you lose your local changes. I'm sure there's a
> way around it but, I'm not sure how just yet.

Yes, Eric points into right direction.

To use dnmasq, you need to disable DHCP and use static configuration for 
SLiRP. Don't worry about addresses, because DHCP-Server inside SLiRP 
give the guest the same address every time. So, static or DHCP does not 
matter.
http://colinux.wikia.com/wiki/Network#SLiRP_with_Static_IP_Address

In config of dnmasq you must set 10.0.2.3 and your DNS from VPN.
In static network configuration of SLiRP you should set "nameserver 
localhost" in /etc/resolv.conf.

-- 
Henry N.