Re: nlb mode
From: Juan (Juan_at_discussions.microsoft.com)
Date: 11/10/04
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Date: Wed, 10 Nov 2004 05:44:03 -0800
Ok based on this information I would use multicast without a doubt.
But just for your own knowledge I would do some testing and see how much
flooding unicast will actually cause in your network setup. I used MRTG to
take snap shots and in my environment it wasn’t that bad between unicast and
multicast I’m also using Cisco switches verses Dell switches but I’m not sure
how much of a factor that would be.
I do agree with you about adding the 2nd nic and having to use that for
inter-host communication, its more streamline and efficient to just use
multicast.
Do not forget to update your gateway for those to web servers and add any
static arp entries if required by your router.
Juan
"Param R." wrote:
> Hi Juan,
>
> Thanks for the great information. Here is my setup:-
>
> 1. Dell 5324 Ethernet Switch (Layer 2)
> 2. 2 Servers - Windows Server 2003 Web Edition (NLB) - 2 NICS Teamed.
> 3. I have DC & DB Servers too.
> 3. I would need inter-host communication for the same reason as you: to move
> website content updates from 1 server to another.
> 4. Now I could do Unicast & add a 2nd nic to each server, but I dont want
> switch flooding as my network will get clogged.
>
> Based on this what would you recommend?
>
> thanks,
> Param
>
>
> "Juan" <Juan@discussions.microsoft.com> wrote in message
> news:27A9F9FD-BD48-4A9B-B18F-2D09DDDC80B7@microsoft.com...
> > Hi,
> >
> > In my experience I have used both unicast and multicast.
> >
> >
> > It all depends on what your NLB hosts will be doing and if they need to
> > perform inter-host communication between each other.
> >
> > If your nodes do not need to see each other I would leave the default mode
> > unicast and deploy the NLB clusters but this mode those flood all of the
> > switch ports.
> >
> > If the nodes in the NLB cluster need to see each then multicast would be a
> > good choice.
> >
> > Both modes of operation have their pros and cons. The advantages of
> > unicast
> > mode are that it works seamlessly with all routers and layer-2 switches
> > (and
> > layer-3 switches which are configured to operate in layer-2 mode).
> >
> > The disadvantages are:
> > . Unicast mode induces switch flooding, where all switch ports are flooded
> > with NLB traffic, even ports to which non-NLB servers are attached;
> > . Since all hosts in the cluster have the same IP Address and the same MAC
> > Address, there is no inter-host communication possible between the hosts
> > configured in unicast mode.
> > Multicast allows inter-host communication because it adds a layer two
> > multicast address to the cluster instead of changing it and this makes
> > inter-host communication possible as the hosts retain their original
> > unique
> > MAC addresses and already have unique Dedicated IP Addresses. However, in
> > multicast mode, the ARP reply sent out by a host in the cluster, in
> > response
> > to an ARP request, maps the clusters unicast IP Address to its multicast
> > MAC
> > Address. Such a mapping in an ARP reply is rejected by some routers and so
> > administrator must add a static ARP entry in the router mapping the
> > Cluster
> > IP Address to its MAC Address
> >
> > Example in my experience why I chose multicast versus unicast was that all
> > web content on the NLB hosts had to be identical.
> >
> > And updating the content was only performed on 1 of the nodes then the
> > data
> > from that node was replicated out to all the other nodes. This requires
> > inter-host communication.
> >
> > Regards,
> >
> > Juan
> >
> >
> >
> > "Param R." wrote:
> >
> >> Hi all, we are in the process of setting up a new NLB environment running
> >> 2003 Web. What is the recommended NLB Mode for performance and
> >> manageability? Unicast or MultiCast? All servers have dual INTEL gigabit
> >> nics. The switches are Dell 5324 Gigabit switches etc.
> >>
> >> TIA!
> >>
> >>
> >>
>
>
>
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