[Bridge] [PROBLEM] mac address learned on wrong port

Seweryn Niemiec ser at man.szczecin.pl
Wed Apr 27 13:17:01 UTC 2016

On 26.04.2016 18:49, Stephen Hemminger wrote:
> This usualy happens when you either have a loop or packet leaks in from other port.

Yeah, it looks like a loop, but p2p1 is connected to a production network with 
running MSTP, so I was sure there is no loop, but I have double checked it today 
and I'm still sure there is no loop in the net outside of the server. To make it 
super sure I have connected p2p1 to a dead end port (vlan with this one port 
only) on a switch and the effect was the same - container's mac is learned on p2p1.

Could you explain what you mean by packet leaking in from other port?

I have one more clue:

when I do:

# arping -c1 ip-of-gateway

inside the container, then on host I can observe:

tcpdump -en -i vethV05BAQ ether src host 00:16:3e:aa:aa:66

14:57:17.528848 00:16:3e:aa:aa:66 > ff:ff:ff:ff:ff:ff, ethertype ARP (0x0806), 
length 42: Request who-has tell, length 28
14:57:17.528915 00:16:3e:aa:aa:66 > ff:ff:ff:ff:ff:ff, ethertype ARP (0x0806), 
length 60: Request who-has tell, length 46

Two packets of same content, but different sizes. Difference is a padding of eth 
frame to 64 bytes.

Does it mean something?

Best regards,
Seweryn Niemiec

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