[ale] failover planning

[Stephan Uphoff]

On Mon, 2004-11-29 at 20:34, Christopher Fowler wrote:
> I've tried this before with simple configuration of two nics simply
> using ifconfig.  But I was never convinced that packets destined for 2.5
> was not scooped up by the first nic on 2.4

When I transitioned from cable to dsl I had such a setup.
The problem was that BOTH nics would reply to broadcasted ARP request
for either of the IPs with their own Ethernet address.
This caused packets to arrive at the wrong interface where they were
blocked by a firewall. (This was an old hacked up 2.2.16? kernel)

> 
> On Mon, 2004-11-29 at 20:27, Bob Toxen wrote:
> > On Mon, Nov 29, 2004 at 07:49:43PM -0500, Christopher Fowler wrote:
> > > Speaking of failover is it possible to install 2 NICS in Linux and put
> > > them on the same subnet.  I.E. eth0 = 192.168.1.4 and eth1 = 192.168.1.5
> > > then place those NICS under load balancing.  In this case both will have
> > > the same DNS and same gateway.  All load balancing setups I've seen load
> > > balance between multiple Internet connections.
> > Sure.  No problem.  Of course, this is needed only if your total bandwidth
> > requirements exceed that of a single NIC (either 100 Mbps duplex or 1 Gbps).
> > 
> > Bob Toxen
> > bob at verysecurelinux.com               [Please use for email to me]
> > http://www.verysecurelinux.com        [Network&Linux/Unix security consulting]
> > http://www.realworldlinuxsecurity.com [My book:"Real World Linux Security 2/e"]
> > Quality Linux & UNIX security and SysAdmin & software consulting since 1990.
> > 
> > "Microsoft: Unsafe at any clock speed!"
> >    -- Bob Toxen 10/03/2002
> > 
> > 
> > > On Mon, 2004-11-29 at 19:40, Greg Freemyer wrote:
> > > > On Mon, 29 Nov 2004 09:51:34 -0500, James P. Kinney III
> > > > <jkinney at localnetsolutions.com> wrote:
> > > > > I am looking at setting up a small non-local redundant webserver. The
> > > > > net access for each node is through different ISP's so each node has
> > > > > different IP's. In fact, there is nothing in common between the two
> > > > > different networks. They have no common router.
> > > > > 
> > > > > The main site is serverd by a T1 line that is susceptable to an outage
> > > > > caused by falling trees. I would like to make the outage as short as
> > > > > possible by making the backup site live as fast as possible. Right now,
> > > > > other than editing the DNS listing and waiting for the change to
> > > > > propogate, I have no other way to do this.
> > > > > 
> > > > > Any suggestions?
> > > > > --
> > > > > James P. Kinney III          \Changing the mobile computing world/
> > > > 
> > > > If nothing else, you could try round-robin DNS.
> > > > 
> > > > That way roughly half of your dns quiries will go to each IP.
> > > > 
> > > > Then set your client TTL low so your users are requesting a new DNS
> > > > entry fairly often.
> > > > 
> > > > If one of your sites fails,  there is a 50% chance your users will go
> > > > to the other site with their next DNS request.  (ie. if you have M$
> > > > users, they do a dns request at least once per reboot.)
> > > > 
> > > > Greg
> 
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