VGT Mode and untagged traffic

zeebahi — Sat, 28 Nov 2020 23:25:04 GMT

Hi everybody,

I was under the impression when we use VGT mode ( vlan 4095) on a standard switch, attached VMS on the standard switch, is supposed to send/receive tagged traffic. But I see it is not necessarily true:

TEST SET UP;

CSR1-gig3-200.200.200.10/24-------PORT-GROUP: LAN , VLAN 4095

CRS4-gig2-200.200.200..4/24----------- |

Above we have two VMS ( Cisco CSR routers) which are configured to send/receive untagged traffic, CSR1 has gig 3 and CSR4 has gig3 in port group LAN, which has vlan id 4095.

CSR1#show running-config interface gigabitEthernet 3

Current configuration : 93 bytes
interface GigabitEthernet3
ip address 200.200.200.10 255.255.255.0

SR4#show running-config interface gigabitEthernet 2
interface GigabitEthernet2
ip address 200.200.200.4 255.255.255.0

########################################

CSR4 can ping CSR1:
CSR4#ping 200.200.200.10
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 200.200.200.10, timeout is 2 seconds:
!!!!!

Packet capture on gig 2 on CSR4 shows untagged traffic being sent out:

###############################################################

Is it a bug or expected behavior for VGT mode?

Thanks and have a good weekend!!

Re: VGT Mode and untagged traffic

scott28tt — Sun, 29 Nov 2020 08:27:14 GMT

@zeebahi

Moderator: Moved to vSphere vNetwork Discussions

Re: VGT Mode and untagged traffic

a_p_ — Sun, 29 Nov 2020 10:59:09 GMT

VLAN 4095 does not restrict traffic to tagged traffic only. It just allows for VGT, which means that VLAN tags will neither be added, nor removed from ingress/egress network frames by the port group. It's the guest's sole responsibility to handle the frames, i.e. send them tagged, or untagged.

André

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VGT Mode and untagged traffic

Re: VGT Mode and untagged traffic

Re: VGT Mode and untagged traffic