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The board has approved the change in MAC address limit from 5 to 1. NOTE: This is orthogonal to the dedicated remote switch question, which is still pending. Non-dedicated remote switches can, for example, enforce this per-VLAN. We have already confirmed that most participants are using only 1 MAC address, and some that were using more than 1 have addressed that after being contacted. As discussed below, this change will be rolled out in a way to keep everyone working, by grandfathering if necessary. On 10/28/19 3:25 PM, Richard Laager wrote: > We have discussed this a bit in the past, and this came up at the last > UG. I'm looking for feedback from the group before formally proposing > this to the board for a vote. > > I first brought this up to the technical committee, CCing the board. I > have heard no objections. Jeremy is "in favor of it 100%". > > Based on our quick conversation after the UG, I _think_ Anthony is in > favor as well; we both made notes to follow up on this. > > ----- > > I am proposing that MICE change its MAC address limit from 5 MACs per > port to 1 MAC per port. 1 MAC address is enough for normal scenarios and > this would further limit the potential for problems on the fabric. This > restriction is one that SIX and AMS-IX both have, with the latter being > known for their excellent configuration guide for participants: > https://www.ams-ix.net/ams/documentation/config-guide > > To be clear, this is still only for end ports, not ports facing remote > switches, of course. The remote switches are responsible for enforcing > the current MAC limit, and would be responsible for changing those > settings as described here. > > If someone is swapping their MICE-facing router, the resulting port flap > on the MICE/remote switch will clear the limit anyway, if they are > directly connected. If they are unable to flap the port (e.g. because > they have someone else's layer 2 gear in the middle), they will have to > either work with that carrier or their switch operator (MICE/remote) to > flap the port. This is a non-zero burden, but I think it's pretty > minimal in practice. Additionally, if someone plans to make an equipment > swap, we would increase the limit in advance, temporarily, upon request. > > For reference, SIX goes further and locks you to a particular MAC > address in an ACL, so you have to contact them to change your MAC. I am > not proposing that. Still, I've been through that a couple of times, and > even that isn't really too big of a deal. So I don't think the change to > a limit of 1 MAC at MICE will be particularly onerous. > > There are a couple of participants who have two IP address sets (one > IPv4 and one IPv6) on the same port. For those ports, the limit > obviously must be at least 2 MACs, but I propose 3 MACs as the limit. If > they're using two IPs, they probably are doing so to get some redundancy > out of it. For this particular use case, needing to flap the port > defeats that redundancy goal, as it breaks the other router. Having a > MAC limit of 3 would allow them to swap a device without needing to flap > the port. We would grandfather these setups until they are looking for a > port-type upgrade; at that point they would need to get to one IP > address set per port (by splitting into two ports or reducing to one IP > address set) or request an exception as outlined below. The exception > process would allow us to better evaluate this use case at that time. > > There are some members who have multiple MACs showing up now, despite > using only one device. For those, I am proposing we set the MAC limit to > however many MACs are currently showing up on their port. That is, they > would be grandfathered at their current situation for now. At the time > of this change, we would encourage them to investigate and fix the > multiple MACs issue at their leisure. In the future, if they are doing a > equipment swap (especially like-for-like), we would again encourage them > to address it, but would otherwise leave their higher limit in place. If > they do a port-type upgrade, we would not bring the grandfathering over. > If they needed, they could ask for an official exception at that time. > > There may be cases where people cannot reasonably fix their routers to > use only 1 MAC, other scenarios I haven't considered, or things that may > come up in the future. For that reason, I think we should allow for the > possibility of exceptions upon request to the board. In practice, I > would expect the board would confer with the technical committee and/or > the technical committee would be bringing these to the board anyway. The > goal is to strike a reasonable balance between protecting the fabric > without preventing networks from connecting. > -- Richard