[j-nsp] EX4200 LLDP issue with vlan-tagging

[Stacy W. Smith]

I hate trying to read IEEE standards, but after a cursory glance I would agree that the behavior your seeing on the vlan-tagged family inet interface is not correct.

I didn't see anything specifying one way or another in the 802.1AB-2005 (LLDP) standard, but the 802.1Q-2005 standard says this in Table 9-2: "The null VLAN ID. Indicates that the tag header contains only priority information; no VLAN identifier is present in the frame. This VID value shall not be configured as a PVID or a member of a VID Set, or configured in any Filtering Database entry, or used in any Management operation."

I interpret "or used in any Management operation" to exclude the use of a vlan tag value of 0 for LLDP frames.

Of course the simple fact that the two different configuration are producing different frame formats should be enough to get JTAC to investigate more thoroughly.

--Stacy

On May 10, 2011, at 3:11 AM, Jeff Wheeler wrote:

> I find that EX4200 with interfaces configured with vlan-tagging and
> layer-3 sub-interfaces, as opposed to family ethernet-switching and
> routed VLAN interfaces, transmit LLDP frames differently.  I do not
> think this is the correct behavior, but I would appreciate comments.
> 
> The interfaces configured as follows:
> interface xe-1/1/1 {
>  vlan-tagging;
>  unit 3911 {
>    vlan-id 3911;
>    family inet {
>      address 192.0.2.1/24;
>    }
>  }
> }
> produces LLDP frames that appear like this:
> 08:39:23.892264 Out 00:19:e2:51:86:99 > 01:80:c2:00:00:0e, ethertype
> 802.1Q (0x8100), length 68: vlan 0, p 0, ethertype LLDP, LLDP,0
> 
> Notice the outer-ethertype 0x8100 rather than 0x88CC.  Surely this is
> not correct.
> 
> Changing the configuration to something like:
> interface xe-1/1/1 {
>  unit 0 {
>    family ethernet-switching {
>      port-mode trunk;
>      vlan {
>        members 3911;
>      }
>    }
>  }
> }
> interface vlan.3911 {
>  family inet {
>    address 192.0.2.1/24;
>  }
> }
> vlan v3911 {
>  vlan-id 3911;
>  l3-interface vlan.3911;
> }
> produces LLDP frames which appear normal:
> 08:50:01.121422 Out 00:19:e2:51:86:bf > 01:80:c2:00:00:0e, ethertype
> LLDP (0x88cc), length 74: LLDP, name J3K3.1250RL, length 60
> 
> In the first case, my neighboring devices are dropping the LLDP
> frames, and thus they do not learn about the advertising device.  In
> the later case, everything works as expected.  With both
> configurations, the EX4200 itself does detect the neighboring
> LLDP-speakers correctly.
> 
> -- 
> Jeff S Wheeler <jsw at inconcepts.biz>
> Sr Network Operator  /  Innovative Network Concepts
> 
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