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Old 12-08-2014, 07:18 AM   #1
Nemesiz
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Linux bond mode 3 (broadcast)


Hello,

I have a situation there I need to use bond broadcast mode. I`m studying this mode and I don't understand in some point.

For example there are 2 machines A and B both have 2 NIC. They are connected directly A etc0 <-> B eth0 and A eth1 <-> B eth1. The bond is working.
Then the packet are send from A eth0 its arrives to B eth0 and the same from A eth1 to B eth1. But the reply goes like B eth0 wants to delivery to A eth0 and A eth1, and B eth1 to A eth0 and A eth1.

A bond0

Quote:
# ping 192.168.20.1
PING 192.168.20.1 (192.168.20.1) 56(84) bytes of data.
64 bytes from 192.168.20.1: icmp_req=1 ttl=64 time=6.85 ms
64 bytes from 192.168.20.1: icmp_req=1 ttl=64 time=7.20 ms (DUP!)
64 bytes from 192.168.20.1: icmp_req=1 ttl=64 time=7.47 ms (DUP!)
64 bytes from 192.168.20.1: icmp_req=1 ttl=64 time=7.80 ms (DUP!)
^C
--- 192.168.20.1 ping statistics ---
1 packets transmitted, 1 received, +3 duplicates, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 6.855/7.334/7.808/0.360 ms
B eth0

Quote:
13:11:59.562443 IP 192.168.20.2 > 192.168.20.1: ICMP echo request, id 34545, seq 1, length 64
13:11:59.562473 IP 192.168.20.1 > 192.168.20.2: ICMP echo reply, id 34545, seq 1, length 64
13:11:59.562860 IP 192.168.20.1 > 192.168.20.2: ICMP echo reply, id 34545, seq 1, length 64
B eth1

Quote:
13:11:59.562475 IP 192.168.20.1 > 192.168.20.2: ICMP echo reply, id 34545, seq 1, length 64
13:11:59.562840 IP 192.168.20.2 > 192.168.20.1: ICMP echo request, id 34545, seq 1, length 64
13:11:59.562865 IP 192.168.20.1 > 192.168.20.2: ICMP echo reply, id 34545, seq 1, length 64
Does the broadcast mode have to work like this?
 
Old 12-09-2014, 02:38 PM   #2
nini09
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Yes, broadcast mode work like this. This mode transmits everything on all slave interfaces.
 
Old 12-09-2014, 03:29 PM   #3
Nemesiz
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Yes manual says it. But the problem is that server A sends single packet it will go out from A eth0 and A eth1 and arrives in B eth0 and B eth1 = 2 packets total one in each NIC = good. But the reply goes double. Instead B sends one packet in each NIC etc0 and eth1 it sends clone packet additional. And this appears everywhere [ TCP, ICMP, ARP ]
 
Old 12-11-2014, 02:31 PM   #4
nini09
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Normal again. Check following comment. Four ping reply are normal because two ping request.

1) ping request 34545 on eth0 of server A -> eth0 of server B
11) ping reply 34545 on eth0 of server B for ping request 34545 on eth0 of server B
12) ping reply 34545 on eth1 of server B for ping request 34545 on eth0 of server B

2) ping request 34545 on eth1 of server A -> eth1 of server B
21) ping reply 34545 on eth0 of server B for ping request 34545 on eth1 of server B
22) ping reply 34545 on eth1 of server B for ping request 34545 on eth1 of server B
 
Old 12-11-2014, 04:33 PM   #5
Nemesiz
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https://www.kernel.org/doc/Documenta...ng/bonding.txt

Quote:
broadcast: This mode is really a special purpose mode, and is suitable
only for very specific needs. For example, if the two
switches are not connected (no ISL), and the networks beyond
them are totally independent. In this case, if it is
necessary for some specific one-way traffic to reach both
independent networks, then the broadcast mode may be suitable.
So bond mode 3 does not have any method to drop duplicated packets and delivery to program or another network single packet.

Are there any other method to do it ?
 
Old 12-12-2014, 03:48 PM   #6
nini09
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Other modes transmit packet of one copy only except mode 3. Normally, mode 4 is used.
 
  


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