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Re: [Linux-cluster] OT: how to monitor VLAN membership


I can't see how your problem could be solved.

Your wrong switch, as long as it has ports UP in a given Vlan (your
physical hosts) , wether or not this Vlan is well propagated to its
adjacent switches, will consider the Vlan being UP (not pruned).

Every host (physical) connected to this switch will see each other (at
MAC level and IP for your VM's)  but not the ones connected to other
switches on the same Vlan.

>From what I can guess, your switch is connected to other ones thru
trunks (802.1q Vlan tagged links) but this specific VlanID was not
propagated between all the switches.

This is generally  due to a misconfiguration, ie on IOS cisco based
switches switchport trunk allowed vlan 1, x, y except your specific VM

The only way to address this would be to have a L3 (IP) interface
configured on your core switches (not on the leaf ones where your
hosts are physically connected) on which the Vlan is present and test
it thru ping.


2009/10/13, Gunther Schlegel <schlegel riege com>:
> Hi,
> this is a bit OT, but definitely cluster-related.
> I am looking for a way to test the switch VLAN configuration from my RHEL5.4
> cluster nodes.
> The cluster is running Virtual Machines as services, there is a network
> bridge for each VLAN configured on the each of the nodes. The cluster nodes
> itself have no need to access the VM's VLANs, so the bridges do not have any
> IP assigned to it. As the VMs may be migrated between the nodes, it is
> crucial that every node may use any required VLAN.
> While we do monitor the switch configuration, we came accross a broken
> switch, which seemed to work but did not forward some VLANs although the
> configuration was correct. I would like the nodes to test whether they have
> access to a given VLAN themselves to recognize that situation.
> As there are no IPs assigned to the bridges, simple ping-style tests are not
> an option. I tried to find something based on arp, but have not been
> successful yet.
> Any hint is highly appreciated.
> best regards, Gunther
> --
> Gunther Schlegel
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