Packets going to Gateway MAC instead of host MAC in same subnet

dbgreekas · ‎11-04-2011

I have a strange situation:

Host A is physical and connected to a switch port directly

Host B is virtual (VMWARE) and is on a vSwitch which is connected directly to the same switch as host A

Spanning the ports these hosts use I am finding something strange:

If some other host C,D, or F pings these I get the expected captures of seeing the source and destination hosts macs.

When looing at traffic between Host A and Host B they are using the MAC of the default gateway to communicate as if they don't think they are on the same subnet.

However I have reviewed the config of each twice

- Both have the correct subnet IP and mask

- Both have each others MAC in their arp cache

Any tips as to why this might happen? I am having intermittent connectivity issues between them, and have replaced the cabling and changed the switch ports already... They only seem to have trouble communicating with each other on occasion.

cadet alain · ‎11-04-2011

Hi,

are they in the same VLAN?

Regards.

Alain.

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dbgreekas · ‎11-04-2011

They should both be in the "Default" vLan however as we all know "Default" means something differnet to each vendor "no tag, 0 or 1"

There is no explicit tagging begin done in VMware and both ports are in their default mode and when doing a listing on vLan membership on the cisco switch both both appear to be members of VLAN 1 as expected.

cadet alain · ‎11-04-2011

Hi,

can you post sh interface switchport output for the 2 ports.

Alain.

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dbgreekas · ‎11-04-2011

show interface GigabitEthernet 0/17 switchport

Name: Gi0/17

Switchport: Enabled

Administrative Mode: dynamic auto

Operational Mode: static access

Administrative Trunking Encapsulation: negotiate

Operational Trunking Encapsulation: native

Negotiation of Trunking: On

Access Mode VLAN: 1 (default)

Trunking Native Mode VLAN: 1 (default)

Administrative Native VLAN tagging: enabled

Voice VLAN: none

Administrative private-vlan host-association: none

Administrative private-vlan mapping: none

Administrative private-vlan trunk native VLAN: none

Administrative private-vlan trunk Native VLAN tagging: enabled

Administrative private-vlan trunk encapsulation: dot1q

Administrative private-vlan trunk normal VLANs: none

Administrative private-vlan trunk associations: none

Administrative private-vlan trunk mappings: none

Operational private-vlan: none

Trunking VLANs Enabled: ALL

Pruning VLANs Enabled: 2-1001

Capture Mode Disabled

Capture VLANs Allowed: ALL

Protected: false

Unknown unicast blocked: disabled

Unknown multicast blocked: disabled

Appliance trust: none

show interface GigabitEthernet 0/9 switchport

Name: Gi0/9