Re: Reg. hidden patch with redhat 7.3 kernel [RESEND]

There seem to have been some mailserver glitches, so I am resending my 
reply to Shanti Katta's question about hidden interfaces:

On 26 Jul 2002, Mike McLean wrote:
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I have successfully applied the hidden patch with both 7.2 and 7.3 kernels.

*However*, the optimum solution for Direct Routing with recent RedHat
kernels is to use the transparent proxy or redirect approach.
See http://www.linuxvirtualserver.org/docs/arp.html

In a nutshell, you *don't* assign the VIP to any interface on the real
servers, instead you make an iptables rule like the following *on each
real server*.

iptables -t nat -A PREROUTING -d $VIP -j REDIRECT

You can tune this to make it more picky if you want (select by protocol,
interface, etc), but generally if the real server is seeing a packet
destined for the VIP we probably ought to accept it.

What this rule does is cause the real server to masquerade those packets
to itself.  The overhead of the masquerade is small,... very small
compared to the gains of direct routing, and there is absolutely no arp
problem.

The only hassle is that you have to deal with the masquerade.  Servers
have to be configured to send the right hostnames/ip addresses to
clients, etc, but this is a standard issue web services have to face anyway.


Shanti Katta wrote:
  > Hi,
  > We are trying to deploy the linux virtual server cluster with director
  > and real-servers running RedHat 7.3 via Direct-Routing. As stated in
  > lvs-docs, we are encountering the arp problem. When I tried to apply the
  > hidden patch to RedHat 7.3 kernel, it gives like 2 errors. Going through
  > piranha-list mailing list archives, I found that hidden patch can be
  > applied to RedHat 7.2 kernel without any problems. How far is it true?
  > Also, can anyone suggest how the arp issue can be resolved without
  > compiling the kernel from kernel.org with hidden patch applied but just
  > with redhat 7.3 kernel?
  >
  > Thanks in advance
  > -Regards
  > -Shanti
  >
  >
  >
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