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Hey guys,
I would like to have to following flow with A and B being two different
networks (one public and one private range) on the same load balancer.
InternetClient-->VIPA-->RIPA1orRIPA2-->VIPB-->RIPB1orRIPB2
^........replyA........'^........replyB.......'
*Description*
A client hits a serverA in pool A via VIPA which serverA with its RIP (RIPA1 or
RIPA2) will hits VIPB and will receive an answer from a server in pool B.
Everything works until RIPA1 or RIPA2 tries to connect to VIPB. The packets
arrives from RIPA1 or RIPA2 on the load balancer (lb1) then nothing, it's like
the packet disappears.
lb1 is both networks A _and_ B and only use one gateway, gateway from A.
lb1 eth0=123.2.2.20/24 - gw is 123.2.2.1
lb1 eth1= 10.1.1.10/24 - no gw
A servers are only in network A and use their respective gateway for this
network
VIPA=123.2.2.21/24 (on eth0 so gw is 123.2.2.1)
RIPA1=123.2.2.22
RIPA2=123.2.2.23
B servers are only in network B and use their respective gateway for this
network
VIPB=10.1.1.11/24 (on eth1 so gw is still 123.2.2.1)
RIPB1=10.1.1.12
RIPB2=10.1.1.13
*Screenshots*
lb1# ipvsadm -Ln
-> RemoteAddress:Port Forward Weight ActiveConn InActConn
TCP 123.2.2.21:443 rr
-> 123.2.2.22:443 Route 1 0 0
-> 123.2.2.23:443 Route 1 0 0
TCP 10.1.1.11:80 rr
-> 10.1.1.12:80 Route 1 0 0
-> 10.1.1.13:80 Route 1 0 0
lb1# netstat -nr
Destination Gateway Genmask Flags MSS Window irtt Iface
123.2.2.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0
10.1.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth1
0.0.0.0 123.2.2.1 0.0.0.0 UG 0 0 0 eth0
lb1# tcpdump -i eth1 ip dst 10.1.1.11 -n
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth1, link-type EN10MB (Ethernet), capture size 65535 bytes
19:18:50.969769 IP 123.2.2.23.60877 > 10.1.1.11.http: Flags [S], seq
1331246417, win 5840, options [mss 1460,nop,nop,TS val 1603281160 ecr
0,nop,wscale 7], length 0
lb1# arp -a
RIPA1(123.2.2.22) at 00:18:51:28:aa:d3 [ether] on eth0
RIPB1 (10.1.1.12) at 00:18:51:5f:cd:11 [ether] on eth1
RIPA2 (123.2.2.23) at 00:18:51:e0:c6:e3 [ether] on eth0
gwA (123.200.162.193) at 00:18:19:9e:cf:ef [ether] on eth0
RIPB2 (10.1.1.13) at 00:18:51:9f:88:bd [ether] on eth1
*What I see*
Everything is load balanced properly in pool A 123.2.2.0/24 from ANY networks.
Everything is load balanced properly in pool B 10.1.1.0/24 from this network
ONLY. So any client in 10.1.1.0/24 will be load balanced and will hit RIPB1 or
RIPB2.
But when lets say RIPA1 (123.2.2.22) sends a packet to VIPB (10.1.1.11). I see
the packet coming in via eth1 on the loadbalancer lb1 and then nothing. No ARP
rewrite nothing. Weirdly enough, desperate, I changed the gw on lb1 to be
10.1.1.1, gateway of B. So it's not 123.2.2.1 anymore. And guess what then it
works but I lose a working pool A. It's like I cannot have both. So why should
I have a gateway to make it work ? The packet is coming on the right interface
(eth1) therefore the good network, so an ARP rewrite should happen and bob's
your uncle... except it's not ;)
*What I CANNOT see*
A packet coming on one of the B server (RIPB1 or RIPB2)
*Questions*
1. So is it possible to use one load balancer to load balance 2 differents
network __AND__ let the servers in the pools to hit each others. Or is it wrong
by design ?
2. Where is the packet going on the load balancer ? How can I track it ?
(tcpdump is not enough or I am doing it wrong):
*Software*
- Centos 6.2 - kernel: 2.6.32-220.4.2.el6.x86_64
- keepalived
- VMs on VMWare with VMXNET3 NICs
Thanks for reading so far. Any kind of hints will be greatly appreciated. I am
really curious to understand why this happens.
Cheers,
Tom
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