topic Re: VLAN connection problems in Switches, Hubs, and Modems

VLAN connection problems

Andre Doeking — Wed, 30 Sep 2009 06:06:29 GMT

Hello!

We have an easy-setup networks consists of nearly 10 HP procurve 5406/12 switches.

After introducing a VmWare ESX lab we had adjusted an extra Demo VLAN 67 on the ProCurve switches. A server outside the VLAN 67 cannot connect to servers inside 67, that's ok!

But something strange happens if I change a IP adress of a server inside the VLAN 67 to for example 10.1.1.5. Inside the default LAN there exists a second server with the same IP.

Now we have two server with the same IP adress but in different vlans, there shouldn't be any problems therefore.

But if I ping the server 10.1.1.5 in the normal VLAN, some pings are lost, then some pings are connected, again and again connection lost. Could it be possible that registering the same IP in a VLAN 67 could have affects on the normal LAN?

Yours sincerely

Andrè Döking

Re: VLAN connection problems

Mohammed Faiz — Wed, 30 Sep 2009 08:55:05 GMT

Hi,

That does sound strange. My first thought would be to check to make sure that the VM's haven't been given the same virtual MACs, that would definitely cause issues.
The second check would be, seeing as you are using the default VLAN, to make sure that you don't have VLAN 1 'leaking' anywhere. We've had the similar issues occasionally when people have accidentally untagged VLANs on uplink ports with VLAN 1 also untagged on the other end.

HTH,

Mo

Re: VLAN connection problems

Tijl van der Steeg — Thu, 01 Oct 2009 10:40:00 GMT

Have you tried a "clear arp"?

Also, I'd indeed take a closer look at the VMs, also at VLAN's at the vswitches