[f-nsp] Bouncing L4 Health Checks
Ethan Burnside
burnside at kattare.com
Thu Jun 12 01:03:12 EDT 2003
Tim,
You mean on the servers? Or on the serveriron?
I haven't had any troubles using ssh/pop/http/ftp/etc connecting
directly (by IP) to any of the 4 servers. We're seeing the same
behavior on all 4 of them in the primary datacenter, and on the other
two in the backup datacenter, so I don't think it could be dupe IP's on
the servers.
I should have mentioned that we're seeing the same behavior on both
of the serveriron's, the one at our primary datacenter and the one at
our secondary datacenter. The machines themselves have a variety of
NIC's, mostly nforce, intel, and 3com. They're all linux servers, but
are running a couple of different kernel versions. (2.4.18 and 2.4.20 I
believe.)
Before we had the GSLB setup we didn't really care much about it
because the load balancing still worked ok. (even if it was flapping a
little more than it should.) But now with the GSLB setup, it's sending
out fail-over DNS responses and causing clients to see errors that
really shouldn't be happening.
Not much fun. Appreciate the response though!
Cheers,
~Ethan B.
--
--------------------------
Ethan Burnside - Founder
Kattare Internet Services
http://www.kattare.com
--------------------------
Quoting "Bulger, Tim" <TBulger at ea.com>:
> You don't have some kind of duplicate IP address problem, do you?
>
> -----Original Message-----
> From: Ethan Burnside [mailto:burnside at kattare.com]
> Sent: Wednesday, June 11, 2003 9:29 PM
> To: foundry-nsp at puck.nether.net
> Subject: [f-nsp] Bouncing L4 Health Checks
>
>
> Greetings,
>
> I've been using a ServerIron XL for SLB and GSLB and have been
> seeing the health checks bounce up and down for quite some time now,
> similar to the following:
>
> 0 days 1:7:52 notification L4 server 206.163.128.131
> front-01-800mcmahan port 110 is up
> 0 days 1:7:52 notification L4 server 206.163.128.131
> front-01-800mcmahan
> port 110 is down due to healthcheck
> 0 days 1:7:46 notification L4 server 206.163.128.131
> front-01-800mcmahan
> port 80 is up
> 0 days 1:7:46 notification L4 server 206.163.128.131
> front-01-800mcmahan
> port 80 is down due to healthcheck
> 0 days 1:7:32 notification L4 server 206.163.128.131
> front-01-800mcmahan
> port 110 is up
> 0 days 1:7:32 notification L4 server 206.163.128.131
> front-01-800mcmahan
> port 110 is down due to healthcheck
> 0 days 1:7:31 notification L4 server 206.163.128.131
> front-01-800mcmahan
> port 80 is up
> 0 days 1:7:31 notification L4 server 206.163.128.131
> front-01-800mcmahan
> port 80 is down due to healthcheck
>
> The server itself hasn't really seen any interruptions in
> service.
> I can connect directly to it over and over without trouble. The
> logs
> actually look similar for all of the hosts on the ServerIron, it's
> not
> limited to a single host. All of the hosts are directly connected
> to
> the ServerIron.
>
> I see the same behavior under both of the following images:
>
> Compressed Pri Code size = 1724176, Version 07.3.06T12 Compressed
> Sec
> Code size = 1873161, Version 07.1.21T12 (SLB07121.bin)
>
> If I disable the L4 health checks, it seems to decide to not do
> the
> L7 checks. The status remains "active" seemingly no matter what I
> do,
> (shut down apache, etc.) until I shut down the server at which time
> it
> changes to "enabled". (I assume because of the failure of the L3
> check.) I'd really like to use the L4 checks anyway. It's just
> that
> this "flapping" is causing all kinds of problems with the GSLB stuff.
>
> We're using the GSLB for a backup/failover "we're working on it"
> error
> page and to avoid "cannot connect" errors with smtp, pop3, etc. But
> with the L4 checks failing, we're seeing people ending up on the
> backup,
> despite the primary being fully accessible, etc. I suspect they get
> the
> backup when the L4 checks on the primary fail simultaneously for
> both
> the SLB machines.
>
> TYIA!
>
> Cheers,
>
> ~Ethan B.
>
>
> --
> --------------------------
> Ethan Burnside
> Kattare Internet Services
> http://www.kattare.com
> --------------------------
>
>
>
> Quoting Brent Van Dussen <vandusb at attens.com>:
>
> > You'll need to keep the serveriron and the customers webservers in
> the
>
> > same L2 domain. If the webservers and the serveriron are all part
> of
> > the same
> > customer installation I don't see why it has to be separated out
> into
> > VLAN's.
> >
> > DSR will do everything else that you need it to, just remember that
>
> > you'll have to configure Loopbacks on each of the real servers.
> >
> > If the real servers are in a different subnet than the serveriron
> you
> > can use the source-ip or just put both subnets on the upstream L3
> > device and
> > the serveriron will route health checks up to the router and back
> > down to
> > the real servers.
> >
> > -Brent
> >
> >
> > At 10:36 AM 1/22/2003, Clifton Royston wrote:
> > > I am trying to configure a particular load-balancing+failover
> > setup
> > >for a web customer who will be colo'ed with us, and am wondering
> if
> > >there is a way to do this. I've got 2 original ServerIrons and
> one
> > >ServerIron XL, I'm planning to put this onto the XL.
> > >
> > > I would like the configuration to have the following
> properties:
> > >
> > >1) The ServerIron can determine when any of the real servers is
> > down
> > > (i.e. failover works correctly)
> > >
> > >2) The customer web servers do not have to be physically
> connected
> > > "through" the ServerIron.
> > >
> > >3) The original source IP address of the connection is preserved
> > (they
> > > need that for their logging and analysis.)
> > >
> > >4) Preferably, the customer servers are in their own address
> block
> > and
> > > VLAN (Ethernet broadcast domain.)
> > >
> > > Is there any way to get all of these at one time?
> > >
> > > I know I can achieve 1, 3, and 4 by physically routing their
> > >connection through a ServerIron port dedicated to their VLAN;
> > that's
> > >close to our standard configuration so I'm not showing that here.
>
> > >That's my fallback solution, but I'd like to be able to do this
> > without
> > >dedicating a port.
> > >
> > > I think I could achieve 2, 3, and 4 by defining the servers as
>
> > >"remote" instead of "real" and configuring DSR, but the
> > documentation
> > >seems to imply that the ServerIrons can't automatically detect a
> > failed
> > >server in that case.
> > >
> > > I know I can achieve the combination of properties 1, 2, and 4
> > by
> > >configuring a tagged VLAN on the main Ethernet link to our main
> > switch
> > >and configuring their servers with source NAT like this; this
> > rewrites
> > >the source IP, but routes everything correctly, distributes load
> > >fairly, detects failed servers, and keeps them in their own VLAN:
> > >
> > >server source-ip xx.yy.zz.14 255.255.255.240 xx.yy.zz.1
> > >real server their-server-1 xx.yy.zz.2
> > > source-nat
> > > port http
> > > port http url "HEAD /"
> > >real server their-server-2 xx.yy.zz.3
> > > source-nat
> > > port http
> > > port http url "HEAD /"
> > >server virtual virtual-85 ww.vv.uu.tt
> > > sym-priority 100
> > > port http
> > > bind http their-server-1 their-server-2
> > >
> > > Is there any way to get all of what I want - failover
> detection,
> > not
> > >dedicating a port to put the servers "behind" the ServerIron,
> source
> > IP
> > >preserved, and keeping them in their own VLAN?
> > >
> > > Thanks in advance for any help.
> > > -- Clifton
> > >
> > >--
> > > Clifton Royston -- LavaNet Systems Architect --
> > cliftonr at lava.net
> > >
> > > "If you ride fast enough, the Specialist can't catch you."
> > > "What's the Specialist?" Samantha says.
> > > "The Specialist wears a hat," says the babysitter. "The hat
> makes
> > noises."
> > > She doesn't say anything else.
> > > Kelly Link, _The Specialist's Hat_
> > >_______________________________________________
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> > >foundry-nsp at puck.nether.net
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> >
> >
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