IP Networking

Duplicated Incoming Packets
It is not uncommon to observe a short burst of duplicated traffic when the bonding device is first used, or after it has been idle for some period of time. This is most easily observed by issuing a "ping" to some other host on the network, and noticing that the output from ping flags duplicates (typically one per slave).

For example, on a bond in active-backup mode with five slaves all connected to one switch, the output may appear as follows:

# ping -n 10.0.4.2
PING 10.0.4.2 (10.0.4.2) from 10.0.3.10 : 56(84) bytes of data.
64 bytes from 10.0.4.2: icmp_seq=1 ttl=64 time=13.7 ms
64 bytes from 10.0.4.2: icmp_seq=1 ttl=64 time=13.8 ms (DUP!)
64 bytes from 10.0.4.2: icmp_seq=1 ttl=64 time=13.8 ms (DUP!)
64 bytes from 10.0.4.2: icmp_seq=1 ttl=64 time=13.8 ms (DUP!)
64 bytes from 10.0.4.2: icmp_seq=1 ttl=64 time=13.8 ms (DUP!)
64 bytes from 10.0.4.2: icmp_seq=2 ttl=64 time=0.216 ms
64 bytes from 10.0.4.2: icmp_seq=3 ttl=64 time=0.267 ms
64 bytes from 10.0.4.2: icmp_seq=4 ttl=64 time=0.222 ms
This is not due to an error in the bonding driver, rather, it is a side effect of how many switches update their MAC forwarding tables. Initially, the switch does not associate the MAC address in the packet with a particular switch port, and so it may send the traffic to all ports until its MAC forwarding table is updated. Since the interfaces attached to the bond may occupy multiple ports on a single switch, when the switch (temporarily) floods the traffic to all ports, the bond device receives multiple copies of the same packet (one per slave device).

The duplicated packet behavior is switch dependent, some switches exhibit this, and some do not. On switches that display this behavior, it can be induced by clearing the MAC forwarding table (on most Cisco switches, the privileged command "clear mac address-table dynamic" will accomplish this).

Originally Posted by Sergiu-IT

Helo !
I set up a new server using FreeBSD 6.0-RELEASE. Everything is ok, until I try to connect it to the internet. After I set up the connection I try to ping yahoo.com and I don't get any reply. When I try to ping the gateway I get a lot of replyes for the same packet. It looks similar to this:

Code:

64 bytes from 81.196.150.65: icmp_seq=1 ttl=255 time=0.858 ms
64 bytes from 81.196.150.65: icmp_seq=2 ttl=255 time=0.829 ms (!DUP)
64 bytes from 81.196.150.65: icmp_seq=2 ttl=255 time=0.829 ms (!DUP)
64 bytes from 81.196.150.65: icmp_seq=2 ttl=255 time=0.829 ms (!DUP)

Does anyone have any ideea about where the problem can be ?
Thanks.