Re: Routing interprocess connections between NLB cluster members

Rodney:

Looks like it is "roll up the sleeves" time. I'll post the results to let
anyone lurking know the answer to this.

Thanks for the help.

Ken

"Rodney R. Fournier [MVP]" <rod@xxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote in
message news:eAIup8aiGHA.1204@xxxxxxxxxxxxxxxxxxxxxxx
Testing will prove helpful here huh?

Cheers,

Rodney R. Fournier

MVP - Windows Server - Clustering
http://www.nw-america.com - Clustering Website
http://www.msmvps.com/clustering - Blog
http://www.clusterhelp.com - Cluster Training
ClusterHelp.com is a Microsoft Certified Gold Partner


"Ken L" <kenl@xxxxxxxxxxxxx> wrote in message
news:u2JGo0aiGHA.4512@xxxxxxxxxxxxxxxxxxxxxxx
Rodney:

Thanks for the response. Regarding your last question, the NLB machines
are all set up with dual NIC's with the NLB virtual cluster IP's on one
"front rail" NIC and a dedicated, machine specific IP on the second,
"back rail" NIC. The NLB is run in unicast mode. I had read the NetBIOS
NLB FAQ before, but I don't think it quite applies to what I am doing.

I think I've found a way around the problem. though, by connecting an
extra router to the front rail and back rail switches. I'll set static
route table entries in each of the NLB servers with next-hop addresses
for all load balanced, inter-process, NLB IP's set to the new router.
The new router will be set up with static route table entries as well.
They will forward the traffic received from the back rail to the front
rail, where the packets will then go through the regular NLB machine
filtering / selection process. There will be some overhead associated
with using routing (rather than more efficient switching), but I can
minimize that by using static entries, minimal ACLs and no routing
protocol. I will end up with external traffic coming into the NLB
cluster through the normal NAT-based perimeter routers and front rail
switch. The interprocess traffic will come in via the round-about route
through the back rail/front rail internal router and it's front rail
attachment to the NLB switch.

I think this should work. What do you think?

Ken


"Rodney R. Fournier [MVP]" <rod@xxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote in
message news:OAw6X$AiGHA.4896@xxxxxxxxxxxxxxxxxxxxxxx
Have your tried this - from:
http://www.microsoft.com/technet/prodtechnol/windowsserver2003/technologies/clustering/nlbfaq.mspx

Q. Can I Load-Balance NetBIOS Traffic?
A. Yes, it is possible, though not recommended for File and Print
Services. Ensure that both of the following are true:

1.
NetBIOS requires that the first IP address in TCP/IP must be
used to access shares, so this must be the cluster IP address (this
means you can't have a dedicated IP address). See the KB article System
Error 53 Has Occurred Using Windows NT Load Balancing Service
(http://go.microsoft.com/fwlink/?LinkId=18381) for further discussion.

2.
Set the DisableStrictNameChecking registry value using the
following instructions:

. Start Registry Editor (Regedit.exe).

. Locate and click the following key in the registry:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\LanmanServer\Parameters

. On the Edit menu, click Add Value, and then add the
following registry value:

Value name: DisableStrictNameChecking

Data type: REG_DWORD

Radix: Decimal

Value: 1

. Quit Registry Editor.

. Open a command window.

. Run net stop server.

. Run net start server.



This solution is documented in the KB article Connecting to SMB
Share on a Windows 2000-Based Server May Not Work with an Alias Name
(http://go.microsoft.com/fwlink/?LinkId=18382).



Next, Multicast and IGMP might change your behavior. Are you running
Unicast or Multicast?

Cheers,

Rodney R. Fournier

MVP - Windows Server - Clustering
http://www.nw-america.com - Clustering Website
http://www.msmvps.com/clustering - Blog
http://www.clusterhelp.com - Cluster Training
ClusterHelp.com is a Microsoft Certified Gold Partner


"Ken L" <kenl@xxxxxxxxxxxxx> wrote in message
news:eCf24wZhGHA.3996@xxxxxxxxxxxxxxxxxxxxxxx
This is question is going to seem a bit strange, but hopefully someone
can help me. I am trying to use NLB in a small, two server (Win2003
server) farm in a publicly accessible perimeter network. I have the
usual complement of IIS web and FTP servers, as well as a whole cadre
of homegrown TCP/IP sockets based services. Some of these applications
communicate between themselves using TCP/IP socket-based sessions.
It's this last group, which is sending data between two NLB apps on the
same cluster, that is giving me fits.

I am using NLB in a form of poor-man's automated backup, rather than to
balance traffic across the servers. I have specific port rules set up
for each virtual IP address. I run the duplicate services (active and
started) on both servers, but I have the port rules are set up in
single server mode. The port rules, priorities and apps are set so that
only one of the two machines normally services the traffic for each
specific services. The priority on the second machine is set lower, so
that if the primary server for a service is shut down or fails, the NLB
cluster reconverges, and traffic automatically will transfer to the
backup server. With NLB, we don't have to do anything special (like
starting backup services, changing IP addresses across servers, etc.)
to keep things running on a near continuous basis. The need for this
is real as our offices are only staffed for 10 hours each day, but we
have processing that runs 24x7. We are trying to make failover as
automatic (and cheap as possible).

The inter-process communications TCP/IP sessions are the ones
presenting me with a problem. I want them to automatically fail over to
the remaining server (per the port rules and priority). For NLB to do
its thing, though, all traffic for the servers must be routed through
the network switch which services all servers in the cluster. Take a
look at the excerpt from the route table on one of the NLB servers,
below. The virtual IP addresses of the NLB apps are in the
192.168.12.xx range. Look closely at the entry for 192.168.12.11. Note
that the gateway and interface IP addresses are both set to the
loopback address. This is the same of all of the NLB addresses. If I
try to start an inter-process session to one of these addresses one of
these NLB these addresses, the TCP/IP stack sees the loopback address
is the destination and routes it internally, never sending it to a NIC
or switch for load balancing. My problem occurs if an app tries to
connect to a service which is currently being processed on the opposite
machine. Instead of going through the load balancing (via the switch
and NIC) and being processed by the single-mode machine with the
highest priority, it will instead be swallowed by the TCP/IP stack
(because of the loopback address) and it will be processed by the
service on the local machine. Some of these services are not truly
"stateless" and I need them to only be processed on the machine with
the highest priority. To net this out, I need a way to force the
transaction out to the switch so that it gets seen by all the NLB
servers (and only handled by the one with highest priority).

I tried setting a static route table entry on each server, setting the
gateway addresses for all NLB virtual addresses to the gateway router.
This sent the traffic to the router which then ping-ponged it back
through the switch, but it caused the router to also include with every
packet routed an ICMP re-direct packet (telling the server it has a
closer, more direct route to the address and to stop bothering the
router). This process creates a ton of extra traffic for the router,
which it shouldn't really have to handle, since the switch could very
well have handled the packets. Now my problem is the switches I am
saddled with are just dumb, unmanaged switches without VLANs or IP
addresses on their ports. I can't set a static route to the send the
packet only to the switch because it doesn't have an IP address.

The route command I used to set up the static route was:

route -p add 192.168.12.0 mask 255.255.255.0 192.168.12.2 metric 1
[the router's address is 192.168.12.2]

I am considering setting up the following route command (actually, as
series of commands, one command for each NLB virtual IP address):

route -p add 192.168.12.11 mask 255.255.255.0 192.168.12.11 metric 1

This is similar to the entry in the route table for the 192.168.12.0
network (the 192.168.12.81 gateway IP address is the first IP on on the
NIC). I'm not sure whether this will actually route the traffic out to
the switch, though. I have a feeling that it will only be serviced by
the NIC driver and that the network switch will never get the packet
(so it can forward it to all the NLB servers for marshalling).

Has anyone else come across this same problem and solved it? Specific
example statements showing a solution would be appreciated.


ROUTE TABLE EXCERPT:

Active Routes:
Network Destination Netmask Gateway Interface Metric
0.0.0.0 0.0.0.0 192.168.12.2
192.168.12.81 20
127.0.0.0 255.0.0.0 127.0.0.1
127.0.0.1 1
192.168.12.0 255.255.255.0 192.168.12.81
192.168.12.81 20
192.168.12.11 255.255.255.255 127.0.0.1 127.0.0.1 20
192.168.12.12 255.255.255.255 127.0.0.1 127.0.0.1 20
192.168.12.13 255.255.255.255 127.0.0.1 127.0.0.1 20
192.168.12.21 255.255.255.255 127.0.0.1 127.0.0.1 20
192.168.12.81 255.255.255.255 127.0.0.1 127.0.0.1 20
192.168.12.255 255.255.255.255 192.168.12.81 192.168.12.81
20
255.255.255.255 255.255.255.255 192.168.12.81 192.168.12.81 1
... OMITTED ...
Default Gateway: 192.168.12.2









.

Relevant Pages

  • Re: Routing interprocess connections between NLB cluster members
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