Vswitch arp tables

[butlr0kw]

When I work with our network engineers on ESXi 5 and 5.5 networking problems they often ask for a copy of the arp table in the Vswitch.

I found information on displaying the arp table for the VMKernel port groups but I cannot figure out how to display the arp table for the Virtual Machine port groups.

Does the Vswitch maintain an arp table for Virtual Machine port groups?

[TomHowarth]

Have a read of http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=2000130

that should point you in the right direction

[butlr0kw]

Thanks for the link.

That KB shows how to display the arp table for vmk and it works for that purpose.

I have several port groups defined for virtual machines in various other vlans.

How do I display the arp tables that the Vswitch maintains for these non-vmk port groups?

[TomHowarth]

this post from LamW should help you further

How to query for MACs on internal vSwitch on ESXi | virtuallyGhetto

also you could use

List ARP table entries of an ESXi « Juanma's Blog

[butlr0kw]

Thanks for the links.

Neither link answers my question however.

How to query for MACs on internal vSwitch on ESXi | virtuallyGhetto====================================

The vSwitchInfo.sh is a very nice script that shows a list of MAC addresses for the VMs on an ESXi host.

No MAC to IP information is shown for any devices out in the physical world.

List ARP table entries of an ESXi « Juanma's Blog=================================================

The network neighbor command only shows the ARP table for vm kernel ports.

I have several port groups defined for virtual machines in various vlans.

How do I display the arp tables that the Vswitch maintains for these non-vmk port groups?

[kermic]

Well, I would say that the vSwitch doesn't really hold any ARP tables.

When the frame arrives from outside and enters the vSwitch, vmkernel checks if any connected virtual network cards do have assigned a MAC that the frame has as a "destination MAC". Once a match is found, the frame is processed and sent out on a particular port (where our destionation VM's NIC is connected). If no match is found, packed is dropped.

In case you would like a VM to start receiving or sending frames with a source / destination MAC different from the one assigned to virtual NIC, you'd have to start mocking around with security settings - Promiscuous mode, MAC Changes and Forged Transmits.

ARP is normally done by the OS, not the switch. Remember that VMware vSwitches are L2 devices! (well, apart from the IP-Hash nic teaming and traffic filtering and marking rules you can set up on dVS using IP qualifiers, everything else is pretty much L2).

Hope this helps.

[TomHowarth]

That is to be expected as a VMware vSwitch does not hold a CAM table.  hence the reason that it does not participate in Spanning tree, I only knows about the devices that are directly attached to it.

so VMK, Virtual Machines and it next hop uplinks.