* Re: start up script
2004-03-06 10:43 start up script Ravi Kumar Munnangi
@ 2004-03-06 12:00 ` John Kelly
2004-03-06 17:12 ` Ray Olszewski
2004-03-09 14:09 ` Stephen Samuel
2 siblings, 0 replies; 4+ messages in thread
From: John Kelly @ 2004-03-06 12:00 UTC (permalink / raw)
To: linux-newbie
Hi,
On Sat, 6 Mar 2004 02:43:03 -0800 (PST)
Ravi Kumar Munnangi <munnangi_ivar@yahoo.com> wrote:
> Users,
>
> Iam working in a LAN with a number of systems.
> A system has X hardware address and another has Y
> hardware address.
> I want to set the hardware address of the second
> system
> also to X.
> I also want to set the primary IP addresses of both
> systems to 172.31.19.30.
> So when I ping to 172.31.19.30, both the systems
> should respond.
>
> The topology of LAN we are using is star. All
> systems
> are connected to a Switch.
> Does the settings change when we are using a bus
> topology?
First up I don't think you should be doing this. having two systems with the same
hardware address on a LAN is going to break things in 'interesting' ways. ARP requests
are not likely to work as you expect and the switch is likely to get very confused if
it has the same hardware address answering on two different ports.
But then maybe I am wrong.
For what it is worth, here is an extract from the ifconfig man page:
===================================================================
hw class address
Set the hardware address of this interface, if the device driver supports this
operation. The keyword must be followed by the name of the hardware class and
the printable ASCII equivalent of the hardware address. Hardware classes cur-
rently supported include ether (Ethernet), ax25 (AMPR AX.25), ARCnet and netrom
(AMPR NET/ROM).
====================================================================
So if the hardware supports it, ifconfig can do it.
> My actual goal is to start 2 web servers on two
> systems with same hardware address and same
> primary IP address but with different secondary
> IP addresses. So when a request comes from a
> client, the request has to be seen by both
> systems. I will write some mechanism by which only
> one will respond finally.
To me it sounds like you want some kind of load balancing mechanism.
If it is really necessary for both systems to see a packet, then some form
of forwarding might be what you need.
Hope this helps.
regards,
John Kelly
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^ permalink raw reply [flat|nested] 4+ messages in thread* Re: start up script
2004-03-06 10:43 start up script Ravi Kumar Munnangi
2004-03-06 12:00 ` John Kelly
@ 2004-03-06 17:12 ` Ray Olszewski
2004-03-09 14:09 ` Stephen Samuel
2 siblings, 0 replies; 4+ messages in thread
From: Ray Olszewski @ 2004-03-06 17:12 UTC (permalink / raw)
To: linux-newbie
As someone else already noted, this idea is not as straightforward as you
might think it is. Offhand, I cannot think of a situation in which it is a
good solution. But you know your actual problem better than I do, so let me
tell you what I can about your questions, and leave it to you to decide.
At 02:43 AM 3/6/2004 -0800, Ravi Kumar Munnangi wrote:
>Users,
>
> Iam working in a LAN with a number of systems.
> A system has X hardware address and another has Y
>hardware address.
> I want to set the hardware address of the second
>system
> also to X.
OK. Whether you can do this or not is a hardware issue ... some NICs
support it, but others do not. In any case, read the man page for
"ifconfig" (or maybe "ip", if your system does not use ifconfig) to see the
Linux part of this.
> I also want to set the primary IP addresses of both
> systems to 172.31.19.30.
OK. As you probably already know, you do this the same way you would set
the machine to ANY IP address. The exact details are a bit distro
spcecific, and you don't mention which Linux distro you are using ... you
may use "ifconfig" directly, "ip" directly, or "ifup" in conjunction with a
config file (usually /etc/network/interfaces).
> So when I ping to 172.31.19.30, both the systems
> should respond.
Yes, because ping is pretty good at handling multiple addresses, and icmp
is "connectionless". Whether more complex and TCP-based protocols like http
will also work in this setup is less clear to me ... I'd wonder if anyone
has ever tried it (except as an accidental misconfiguration).
> The topology of LAN we are using is star. All
>systems
> are connected to a Switch.
> Does the settings change when we are using a bus
> topology?
Probably not ... but I am not certain what you mean by "bus" in this
context. Are you referring to some sort of ring network (like an old-style
thinnet LAN)?
> Do I have to write a start up script?
> How should I write?
These are distro-level questions ... and to some extent kernel level. Post
a followup with the usual details on your setup ... what distro, what
version, what kernel version, what NICs and modules ... and I or someones
else might be able to answer this one.
> My actual goal is to start 2 web servers on two
> systems with same hardware address and same
> primary IP address but with different secondary
> IP addresses. So when a request comes from a
> client, the request has to be seen by both
> systems. I will write some mechanism by which only
> one will respond finally.
Before you spend too much time on this approach, you want to think through
the "some mechanism" piece. Hand waving won't do here, and I don't see a
sensible way to create a mechanism that will work.
My best *guess* is that you want to do one of two things --
1. Load balance -- in normal operation, have each server handle
roughly half of the traffic.
2. Failover -- in normal operation, have one server handle all of
the traffic, but have the second ready and waiting to "hot swap" in if the
first should fail.
Either of these needs can be achieved in other, more conventional ways than
what you propose to try. The details depend on the content of the Web site
... how much of it is dynamically generated, and how it is generated, how
often its static content changes, how you intend to keep the two machines'
versions of the Website in sync, and the like ... and may involve a third
host (or even a fourth, if a large, shared database is involved).
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^ permalink raw reply [flat|nested] 4+ messages in thread* Re: start up script
2004-03-06 10:43 start up script Ravi Kumar Munnangi
2004-03-06 12:00 ` John Kelly
2004-03-06 17:12 ` Ray Olszewski
@ 2004-03-09 14:09 ` Stephen Samuel
2 siblings, 0 replies; 4+ messages in thread
From: Stephen Samuel @ 2004-03-09 14:09 UTC (permalink / raw)
To: Ravi Kumar Munnangi; +Cc: linux-newbie
Ravi Kumar Munnangi wrote:
> Users,
>
> Iam working in a LAN with a number of systems.
> A system has X hardware address and another has Y
> hardware address.
> I want to set the hardware address of the second
> system
> also to X.
ifconfig eth0 hw ether 00:56:BA:A4:81:02
> I also want to set the primary IP addresses of both
> systems to 172.31.19.30.
> So when I ping to 172.31.19.30, both the systems
> should respond.
ifconfig eth0 172.31.19.30 [[ may want to set netmask/BC]]
>
> The topology of LAN we are using is star. All
> systems
> are connected to a Switch.
> Does the settings change when we are using a bus
> topology?
Some switches may get confused by having the same
MAC address on two ports... In somes cases, it may
only send a packet to one fo the machines (usually
the last one to use that MAC address))
>
> Do I have to write a start up script?
> How should I write?
Write a regular shell script and then put it in
the proper place. If you have proper rc2.d
script directories, then you can put it near the
SNNnetwork scripts
For RedHat, that would be /etc/rc.d/rc[2345].d/S10network
so you could try S09
Otherwise, put it in the r.local file for those kinds of systems.
Setting the MAC addr needs to be done *BEFORE* you
bring the card up. (or you need to bring it down).
(under Linux)
For RedHat systems, however, you can use the MACADDR=
variable in /etc/sysconfig/network-scripts/ifcfg-eth0
and IPADDR=
The RH scripts do the rest.
For the person who said that some cards don't support this,
I would say that that is very rare to nonexistent..
the MAC address needs to be softwar settable for
things like prosxy arp and bridgng... In 17 years
of playing with ethernet, Idon't rememember *ever* seeing
a card that you couldn't set the MAC address on.
> My actual goal is to start 2 web servers on two
> systems with same hardware address and same
> primary IP address but with different secondary
> IP addresses. So when a request comes from a
> client, the request has to be seen by both
> systems. I will write some mechanism by which only
> one will respond finally.
--
Stephen Samuel +1(604)876-0426 samuel@bcgreen.com
http://www.bcgreen.com/~samuel/
Powerful committed communication. Transformation touching
the jewel within each person and bringing it to light.
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^ permalink raw reply [flat|nested] 4+ messages in thread