Setting up a z/VM guest LAN sniffer

7.1 z/VM guest

You can set up a guest LAN sniffer on a virtual NIC that is coupled to a z/VM® VSWITCH or guest LAN.

Before you begin

You need class B authorization on z/VM.
The Linux® instance to be set up as a guest LAN sniffer must run as a guest of the same z/VM system as the guest LAN you want to investigate.

About this task

If a virtual switch connects to a VLAN that includes nodes outside the z/VM system, these external nodes are beyond the scope of the sniffer.

For information about VLANs and z/VM VSWITCHes, see z/VM: Connectivity, SC24-6267.

Procedure

Set up Linux.
Ensure that the qeth device driver has been compiled into the Linux kernel or that the qeth device driver has been loaded as a module.
Set up z/VM.
Ensure that the z/VM guest virtual machine on which you want to set up the guest LAN sniffer is authorized for the switch or guest LAN and for promiscuous mode.

For example, if your virtual NIC is coupled to a z/VM VSWITCH, perform the following steps on your z/VM system:
1. Check if the z/VM guest virtual machine already has the required authorizations. Enter a CP command of this form:
```
q vswitch <switchname> promisc
```
  where <switchname> is the name of the virtual switch. If the output lists the z/VM guest virtual machine as authorized for promiscuous mode, no further setup is required.
2. If the output from step 1 does not list the guest virtual machine, check if the guest is authorized for the virtual switch. Enter a CP command of this form:
```
q vswitch <switchname> acc
```
  where <switchname> is the name of the virtual switch.
  If the output lists the z/VM guest virtual machine as authorized, you must temporarily revoke the authorization for the switch before you can grant authorization for promiscuous mode. Enter a CP command of this form:
```
set vswitch <switchname> revoke <userid>
```
  where <switchname> is the name of the virtual switch and <userid> identifies the z/VM guest virtual machine.
3. Authorize the Linux instance for the switch and for promiscuous mode. Enter a CP command of this form:
```
set vswitch <switchname> grant <userid> promisc
```
  where <switchname> is the name of the virtual switch and <userid> identifies the z/VM guest virtual machine.
For details about the CP commands used in this section and for commands you can use to check and assign authorizations for other types of guest LANs, see z/VM: CP Commands and Utilities Reference, SC24-6268.