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SubjectConnectivity problem (kernel bug?)

Hello All,

I've expiriencing a problem using 802.1q vlan in linux.
It is possible a bug in Linux networking code.
I've posted this problem to linux-vlan list too.

Ok, about the problem in details.
Here is my network scheme:

| Smart switch with 802.1Q support |
| Port1 Port2 Port3 |
| VLAN1: untagged VLAN1: untagged VLAN1: untagged |
| VLAN2: 802.1Q VLAN2: 802.1Q VLAN2: no |
| [*] [*] [*] |
| | |
| | |
Cisco Linux1 Linux2
(default gateway)

*** Cisco configuration:

interface FastEthernet0/0.1
ip address
encapsulation dot1Q 1 native
interface FastEthernet0/0.2
ip address
encapsulation dot1Q 2

*** Linux1 configuration

interface eth0

interface eth0.2

*** Linux2 configuration

interface eth0

Now about the problem.
In this scheme all hosts can ping each other by ip addresses.
And also cisco and Linux1 can ping each other by ip addresses.

But when I am doing "ping" from Linux2 i did not receive response.
And even more. Linux1 ( *sends* no response at all.

I've tried to analyse this and come to a conclusion that this is Linux1 fault.
Well, what is going on:

1. Linux2 ( send icmp echo request to thru ->
2. Cisco receives it and forwards to Linux2 thru VLAN 2 ->
3. Linux1 receives icmp request thru eth0.2

All of this stages may be observed using tcpdump on Linux1 and Linux2.

4. Nothing happened any more! ==8-O
No reply sends from Linux1!
Not from eth0 nor from eth0.2!

I am expecting that Linux1 will send reply to using eth0 but it
is not happening.

This bug affects not only icmp packets. No communication can be
established between Linux2 and ip at Linux1.

Any ideas? Comments?

Best regards,
Dmitry N. Hramtsov

p.s. my kernel on Linux1 is 2.4.18

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