Mailing List Archive

VS-DR Problem
Hello,

I'm setting up a cluster with 3 lvs nodes and try to find the best mode
for me to work. A masqueraded cluster (all machines 2.2.17, director
with kernel patch) was not a problem, but since it doesn't scale fine
and my tests showed a very high load on the director, I decided to give
the VS-DR scheme a try. I was working on it now for the past three days
without a satisfaying result, and after reading the instructions and arp
problem pages again and again I give a shot there, maybe one of the more
experienced cluster-users can give me the hint I'm missing.

I set up the following net (192.168.121.61 is VIP):


| 192.168.121.0 network
|
---------------------------------------------
| DIRECTOR ganga |
| eth1 192.168.121.71, eth1:1 192.168.121.61|
| eth0 192.168.124.100 |
---------------------------------------------
|
| 192.168.124.0 network, directly switched
|
------------------------
| NODE ganesh |
| eth0 192.168.124.101 |
| lo0:1 192.168.121.61 |
| eth1 192.168.121.73 |
------------------------

eth1 is currently not plugged in to the 192.168.121.0 net.

Forwarding and all the kernel options are activated on the director and
since the VIP is not on a direct connection with the real servers I
don't assume I've got an arp problem here. All other options are enabled
on real servers, too. I tried both variants on the real servers, with
the VIP on lo:1 and eth1 (not plugged in). The problem that I saw is
that the director passes the packets correctly to the real server, but
it can't respond to them correctly. I added a tcpdump snipplet for
further information:


director:

13:46:43.765414 obiwan.johoho.1217 > 192.168.121.61.telnet: S
2448685530:2448685530(0) win 32120 <mss 1460,sackOK,timestamp
25530192[|tcp]> (DF)
13:46:46.762534 obiwan.johoho.1217 > 192.168.121.61.telnet: S
2448685530:2448685530(0) win 32120 <mss 1460,sackOK,timestamp
25530492[|tcp]> (DF)
13:46:48.755522 arp who-has ganesh.joho.ho tell ganga.joho.ho
13:46:48.755679 arp reply ganesh.joho.ho is-at 0:50:4:3c:27:f3

and here the info from the node:

ganesh:~# tcpdump
eth0: Setting promiscuous mode.
tcpdump: listening on eth0
13:46:45.848093 192.168.121.17.1217 > 192.168.121.61.telnet: S
2448685530:2448685530(0) win 32120 <mss 1460,sackOK,timestamp
25530192[|tcp]> (DF)
13:46:48.845260 192.168.121.17.1217 > 192.168.121.61.telnet: S
2448685530:2448685530(0) win 32120 <mss 1460,sackOK,timestamp
25530492[|tcp]> (DF)
13:46:50.838276 arp who-has ganesh.joho.ho tell ganga.joho.ho
13:46:50.838330 arp reply ganesh.joho.ho is-at 0:50:4:3c:27:f3



both are synchronized via ntp, so the timestamps should be correct.
obiwan (192.168.121.17) was the machine from ehich I tried to telnet.
Here's my ipvsadm output:

IP Virtual Server version 1.0.2 (size=131072)
Prot LocalAddress:Port Scheduler Flags
-> RemoteAddress:Port Forward Weight ActiveConn InActConn
TCP 192.168.121.61:telnet wlc
-> ganesh.joho.ho:telnet Route 1 0 0


I hope someone can give me a clue what I'm doing wrong. Thanks in
advance,

--
Regards,


Wiktor Wodecki
Re: VS-DR Problem [ In reply to ]
You don't mention what your default gateways and netmasks are on
each machine. That is important.
The netmask on lo on the node should be 255.255.255.255

I'll bet you need to plug in eth1 on the real-server. Do a tcpdump on
lo, I'll bet your response packets are being routed out lo, since the
client you are trying to connect from is on the .121.x network, and eth1
is down...


On Fri, 8 Dec 2000, Wiktor Wodecki wrote:

>
> eth1 is currently not plugged in to the 192.168.121.0 net.
>

here is your problem...
Re: VS-DR Problem [ In reply to ]
On Fri, 8 Dec 2000, Wiktor Wodecki wrote:

> Forwarding and all the kernel options are activated on the director and
> since the VIP is not on a direct connection with the real servers I
> don't assume I've got an arp problem here.

In case you are still having problems....

In the usual VS-DR setup the real-servers are connected to the same piece
of wire that has the VIP on the director and you do have to handle the arp
problem.

Joe

--
Joseph Mack mack@ncifcrf.gov