I have set up a network topology that has no route outside my host. i.e It's a completely private network. I have two ovs bridges connected to each other via a patch link. The patch link is simply a couple of OVS Patch Ports. Host is running Oracle Linux 7.5. Each of the two ovs bridges has a Virtual Machine(running Oracle Linux 7.5) connected to it. Each VM has two VLAN interfaces (VLAN 24(eth0.24) and VLAN 36(eth0.36)) and each of these VLAN interfaces further have a sub-interface (eth0.24.120 and eth0.36.120). Here is a diagram to explain this better: https://github.com/Vanalytics/public_html/blob/master/ovs-topology.png
Packets from VM1 to VM 2 should ideally traverse 4 interfaces: OL7.5-1st-NIC --> patch-to-ovsbr2 --> patch-to-ovsbr1 --> OL7.5-2nd-NIC But two of these are simply patch ports and not real interfaces, which means once they are setup, packets get forwarded from OL7.5-1st-NIC --> OL7.5-2nd-NIC directly inside the kernel. At this time, Table Open_vSwitch, other:config: vlan_limit=1 (default), "vlan_mode" and "tag" are cleared for all four interfaces. Now, if i set 1. tag=10 on all 4 interfaces, & 2. vlan_mode=dot1q-tunnel for all 4 interfaces, VM1 VLANs can ping their respective VLANs in VM2. These ping packets in tcpdump , do NOT have tag 10 but I do see the VLAN tags. tcpdump -i OL7.5-1st-NIC -nn -e vlan ethertype 802.1Q (0x8100), length 106: vlan 36, p 0, ethertype 802.1Q, vlan 120, p 0, ethertype IPv4, 192.168.3.21 > 192.168.3.20: ICMP echo request, id 6604, seq 1, length 64 Secondly, if i keep everything as above 1. (i.e. tag=10 & vlan_mode=dot1q-tunnel for all 4 interfaces), & 2. set vlan-limit to 2 or 0, VM1 VLANs CANNOT ping their respective VLANs in VM2. tcpdump now shows only vlan 36 but tag with vlan 120 is not present in the destination port. My concerns are: 1. Shouldn't setting vlan-limit=0, tag=10 push tag=10 on all packets leaving VM1 and i should see tag=10 in tcpdump. 2. Does setting vlan-limit=0 mean i can push unlimited tags on the packet ? How can i test this ? Thanks, --Simran
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