Mailing List Archive

[lvs-users] ipvs is not working as load balancer
Hello everybody,

I am trying to configure load balancing for udp protocol using LVS NAT.
For that I have created three virtual instances with ubuntu, one
(192.199.1.1) is load director and others (192.199.1.2 and 192.199.1.3)
are real servers where application based on udp protocol are running. I
have configured ipvsadm and setup iptables in real server.

Real server looks like something below....

root@ubuntutcs:~# ipvsadm -l
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags
-> RemoteAddress:Port Forward Weight ActiveConn InActConn
UDP ipvslb-v3.novalocal:5 rr
-> 192.199.1.2:5683 Masq 1 0 0
-> 192.199.1.3:5683 Masq 1 0 0
root@ubuntutcs:~#
root@ubuntutcs:~#
root@ubuntutcs:~# iptables -t nat -L
Chain PREROUTING (policy ACCEPT)
target prot opt source destination
DNAT udp -- anywhere anywhere udp dpt:5683
to:192.199.1.2:5683
DNAT udp -- anywhere anywhere udp dpt:5683
to:192.199.1.3:5683

Chain INPUT (policy ACCEPT)
target prot opt source destination

Chain OUTPUT (policy ACCEPT)
target prot opt source destination

Chain POSTROUTING (policy ACCEPT)
target prot opt source destination
MASQUERADE tcp -- 192.199.122.0/24 !192.199.122.0/24 masq ports:
1024-65535
MASQUERADE udp -- 192.199.122.0/24 !192.199.122.0/24 masq ports:
1024-65535
MASQUERADE all -- 192.199.122.0/24 !192.199.122.0/24
MASQUERADE all -- anywhere anywhere
root@ubuntutcs:~#
root@ubuntutcs:~#

But the problem is, all requests are forwarding to one real server. More
specifically, requests are only forwarded to that real server which come
first in the nat iptable. So, problem is, what I have configured is just a
proxy server not load balancer. I have used "tcpdump" as packet tracker,
here is the output

root@ubuntutcs:~#
root@ubuntutcs:~# !tcpdump
root@ubuntutcs:~# tcpdump -n -i any port 5683
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on any, link-type LINUX_SLL (Linux cooked), capture size 65535
bytes
15:32:27.044214 IP 10.10.99.22.41252 > 192.199.1.1.5683: UDP, length 39
15:32:27.044347 IP 192.199.1.1.41252 > 192.199.1.2.5683: UDP, length 39
15:32:29.979111 IP 10.10.99.22.41252 > 192.168.1.1.5683: UDP, length 39
15:32:29.979206 IP 192.168.1.1.41252 > 192.168.1.2.5683: UDP, length 39
15:32:33.314250 IP 192.168.1.2.5683 > 192.168.1.1.41252: UDP, length 35
15:32:33.314620 IP 192.168.1.1.5683 > 10.10.99.22.41252: UDP, length 35
15:32:37.178892 IP 192.168.1.2.5683 > 192.168.1.1.41252: UDP, length 35
15:32:37.178964 IP 192.168.1.1.5683 > 10.10.99.22.41252: UDP, length 35
15:32:42.808209 IP 10.10.99.22.52395 > 192.168.1.1.5683: UDP, length 39
15:32:42.808327 IP 192.168.1.1.52395 > 192.168.1.2.5683: UDP, length 39
15:32:45.120500 IP 10.10.99.22.52395 > 192.168.1.1.5683: UDP, length 39
15:32:45.120590 IP 192.168.1.1.52395 > 192.168.1.2.5683: UDP, length 39
15:32:46.984465 IP 192.168.1.2.5683 > 192.168.1.1.52395: UDP, length 35
15:32:46.984534 IP 192.168.1.1.5683 > 10.10.99.22.52395: UDP, length 35

Can anybody help me to understand what is required to modify here to make
it load balancer?

Thanks in advance,
Prasun Bhattacharjee

Tata Consultancy Services
Mailto: prasun.bhattacharjee@tcs.com
Website: http://www.tcs.com
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