On Sat, Nov 30, 2024 at 02:28:34PM -0800, Andrew Strohman wrote: > My personal use case is about simulating ethernet connections and VLAN aware > bridges, so that I can test networking equipment that provides VLAN > functionality with IVL. > https://github.com/andrewstrohman/topology-sim/raw/refs/heads/main/docs/Topology%20Simulation%20for%20Mesh%20Testing.pdf?download= > describes it, if you're interested in more information about it. > > https://docs.google.com/drawings/d/1FybJP3UyCPxVQRGxAqGztO4Qc5mgXclV4m-QEyfUFQ8 > is a diagram that shows what I'm thinking about. This case is not about > duplicate macs, but rather a frame being bridged in a way, such that it passes > through the same bridge twice via different ports depending on the inner > VLAN. In the commit message, this is what I meant by the poorly worded: > "L2 hairpining where different VLANs are used for each side of the hairpin". > > The diagram depicts a network where a layer 2 segment is partitioned by a > L2 (bridging) firewall. I admit that this is contrived and not a typical > way of constructing networks. > > In this case, my testing system would use a 802.1ad bridge to simulate a > VLAN aware bridge between .1q #1 and .1q #2. The problem is that the .1ad > bridge would get confused about which ports hosts A and B are behind. > The bridge would see them behind different ports depending on whether the > packet was heading to, or returning from the bridge mode firewall. > > If these nodes were connected with an IVL .1q bridge instead of the .1ad > bridge, this topology would work. So it's a scenario where connectivity > failure would be due to my testing system (topology-sim) instead of the > networking equipment being tested. What stops you from changing the 802.1ad bridge port pvids to unique values, like 3, 4, 5... instead of 3, 3, 3, and making each other j != i bridge port be a non-pvid member of port i's pvid? That would keep the MAC address isolation per 802.1ad bridge port, and would offer the same level of communication using 100% standard and available tools.
