Re: BFD over VXLAN: Trapping BFD Control packet at VTEP

Santosh P K <> Wed, 31 July 2019 17:44 UTC

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From: Santosh P K <>
Date: Wed, 31 Jul 2019 10:44:13 -0700
Message-ID: <>
Subject: Re: BFD over VXLAN: Trapping BFD Control packet at VTEP
To: Greg Mirsky <>
Cc: Dinesh Dutt <>, rtg-bfd WG <>, "T. Sridhar" <>, Joel Halpern <>,, Martin Vigoureux <>,
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I have checked with implementation in data path. When we receive a packet
with valid VNI then lookup for MAC will happen and it is VTEP own MAC then
it will be trapped to control plane for processing. I think we can have
following options
1. Optional managment VNI
2. Mandatory inner MAC set to VTEP mac
3. Inner IP TTL set to 1 to avoid forwarding of packet via inner IP


Santosh P K

On Wed, Jul 31, 2019 at 9:20 AM Greg Mirsky <> wrote:

> Hi Dinesh,
> thank you for your consideration of the proposal and questions. What would
> you see as the scope of testing the connectivity for the specific VNI? If
> it is tenant-to-tenant, then VTEPs will treat these packets as regular user
> frames. More likely, these could be Layer 2 OAM, e.g. CCM frames. The
> reason to use 127/8 for IPv4, and 0:0:0:0:0:FFFF:7F00:0/104 for IPv6 is to
> safeguard from leaking Ethernet frames with BFD Control packet to a tenant.
> You've suggested using a MAC address to trap the control packet at VTEP.
> What that address could be? We had proposed using the dedicated MAC and
> VTEP's MAC and both raised concerns among VXLAN experts. The idea of using
> Management VNI may be more acceptable based on its similarity to the
> practice of using Management VLAN.
> Regards,
> Greg
> On Wed, Jul 31, 2019 at 12:03 PM Dinesh Dutt <> wrote:
>> Hi Greg,
>> As long as the inner MAC address is such that the packet is trapped to
>> the CPU, it should be fine for use as an inner MAC is it not? Stating that
>> is better than trying to force a management VNI. What if someone wants to
>> test connectivity on a specific VNI? I would not pick a loopback IP address
>> for this since that address range is host/node local only. Is there a
>> reason you're not using the VTEP IP as the inner IP address ?
>> Dinesh
>> On Wed, Jul 31, 2019 at 5:48 AM Greg Mirsky <>
>> wrote:
>>> Dear All,
>>> thank you for your comments, suggestions on this issue, probably the
>>> most challenging for this specification. In the course of our discussions,
>>> we've agreed to abandon the request to allocate the dedicated MAC address
>>> to be used as the destination MAC address in the inner Ethernet frame.
>>> Also, earlier using VNI 0 was changed from mandatory to one of the options
>>> an implementation may offer to an operator. The most recent discussion was
>>> whether VTEP's MAC address might be used as the destination MAC address in
>>> the inner Ethernet frame. As I recall it, the comments from VXLAN experts
>>> equally split with one for it and one against. Hence I would like to
>>> propose a new text to resolve the issue. The idea is to let an operator
>>> select Management VNI and use that VNI in VXLAN encapsulation of BFD
>>> Control packets:
>>> An operator MUST select a VNI number to be used as Management VNI. VXLAN
>>> packet for Management VNI MUST NOT be sent to a tenant. VNI number 1 is
>>> RECOMMENDED as the default for Management VNI.
>>> With that new text, what can be the value of the destination MAC in the
>>> inner Ethernet? I tend to believe that it can be anything and ignored by
>>> the reciever VTEP. Also, if the trapping is based on VNI number, the
>>> destination IP address of the inner IP packet can from the range 127/8 for
>>> IPv4, and for IPv6 from the range 0:0:0:0:0:FFFF:7F00:0/104. And lastly,
>>> the TTL to be set to 1 (no change here).
>>> Much appreciate your comments, questions, and suggestions.
>>> Best regards,
>>> Greg