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behavior while changing vlans

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Martin Joppen
Occasional Advisor

behavior while changing vlans

Hi guys,

if I change a ports vlan from e.g. vlan 3 to vlan 4, does the procurve switch assign the port first to the default vlan and then to vlan 4?

Where may I find such information myself?

I ask this, because I´m interested in the internal behaviour of procurve switches and because we have an error, which affects the default vlan. My colleague just changed a ports vlan.

I am using hp procurve 2610 series.

Best regards,

Martin
14 REPLIES
Mohammed Faiz
Honored Contributor

Re: behavior while changing vlans

Hi,

I don't believe that is the case and I've never experienced anything to suggest that this happens.
In fact we have a few systems that automatically change vlans on our switches when a device connects and we don't see this behaviour there.
What exactly is the error you are seeing when changing vlans?
Martin Joppen
Occasional Advisor

Re: behavior while changing vlans

Hi and thanks for the quick response,

the notification is:

ip: DEFAULT_VLAN: icmp: Unsolicited Echo Reply from 10.1.x.x

In my opinion this happened while changing the vlan, because there was no other event and we never had an error like this.

That´s why I am asking for the internal behavior, because the default vlan wasn´t included in any action.

Best regards,

Martin
Mohammed Faiz
Honored Contributor

Re: behavior while changing vlans

The log reference to the default VLAN is just pointing to the VLAN that the switch has this IP on.
In other words if you are routing to VLAN 1 and your swtich has an IP on VLAN 1 then that message does not necessarily mean that a port was moved to/from VLAN 1.

Do you know what the device with IP 10.1.x.x is?
Martin Joppen
Occasional Advisor

Re: behavior while changing vlans

The device was a Win95-PC in 192.168.4.0/24 net (Vlan4) and it is now a Linux-Thinclient in the 10.1.9.0/24(vlan 1009) net.
Mohammed Faiz
Honored Contributor

Re: behavior while changing vlans

Ok, and are you routing to the network for VLAN 1 on that switch? i.e. can you reach it from other subnets or external hosts?
I don't think the message is related to the change of VLAN.
The behaviour it indicates is that of some rougue traffic, potentially malware/virus related so the reported IP (10.1.x.x) may well be spoofed.
If you're seeing that log message a lot you could do a network capture on that switch to locate the source MAC address of the device sending the ICMP packet.
Martin Joppen
Occasional Advisor

Re: behavior while changing vlans

Hi,

Vlan 1 is not used for productivity. There is no ip-address assigned. The IP/Port where the message came from is the new adress of the new device in vlan 1009 replacing the windows95 device in vlan 4 on the same port.

The message only appeared once, after the new device was attached.

Best Regards,

Martin
Mohammed Faiz
Honored Contributor

Re: behavior while changing vlans

Now that is strange, it could be a software bug on the logging, I'll try and simulate it on one of our 2610's and let you know what I get.
I assume your switch has an IP on one of it's VLANs?
Martin Joppen
Occasional Advisor

Re: behavior while changing vlans

Hi,

at this time it had an ip-address in 192.168.9.x and in the mgmt-vlan. I never had such behavior/message before and after this one. So it is strange, that the default-vlan appeared. That´s why I wanted to know if the port is moved form the "old"-vlan to the default-vlan and then to the "new"-vlan.

Thank you very much for the work you put in here.

Greetings,

Martin
Martin Joppen
Occasional Advisor

Re: behavior while changing vlans

Hi,

it was of course 10.1.9.x vlan 1009 where it had an ip-address at this time. I removed it afterwards, because we only want to have the switches in mgmt-vlan.

Greetings,

Martin
Mohammed Faiz
Honored Contributor
Solution

Re: behavior while changing vlans

Ok, so it is slight bug in the reporting on the switch.
I simulated an icmp echo reply to my test 2610 running R.11.54 and got the below in the log.

W 11/10/10 15:03:07 ip: DEFAU: icmp: Unsolicited Echo Reply from x.x.x.x

And I definitely don't have an IP in the default VLAN.
I could only get the log message to appear however if I sent a valid ping before sending the "extra" reply.
Martin Joppen
Occasional Advisor

Re: behavior while changing vlans

Hi,

I would say, that we can close this topic now, because you proofed that it is a bug.


Thank you very much for testing and your help.

Do you know any in depth documentation, where I can possibly read more about the internal behavior of a procurve switches? I have all guides for the 2610, but are there general techdocs about procurve switching?

Best regards,

Martin
Mohammed Faiz
Honored Contributor

Re: behavior while changing vlans

Hi,

Your welcome :)
I'm afraid I don't know of any documentation that goes to the depth of describing the internal switching/routing mechanisms, it's not something most people are interested in!
Martin Joppen
Occasional Advisor

Re: behavior while changing vlans

Okay,

perhaps I will find some documentation in future.

Thank you again.

I will close this thread now.

Have a nice day!

Martin
Martin Joppen
Occasional Advisor

Re: behavior while changing vlans

The problem with the default vlan seems to be a bug in the logging of the 2610 like Mohammed Faiz found out.

I didn´t find any documentation concerning the internal switching mechanisms.