[j-nsp] loop detection on EX4200

[Ben Dale]

> No, LLDP does not work either across the multiplexer. If I configure a
> vlan tag on the "default" vlan on the EX42, LLDP starts seeing the
> EX42 on the other side.
> 
> That was the reason I had suggested that the multiplexer did not
> forward untagged frames.

That is certainly odd.  Even on a trunked interface with no native-vlan configured at all, LLDP PDUs should still be sent untagged:

bdale at elow-core-01# show interfaces ge-1/1/5                               
vlan-tagging;
unit 3830 {
    vlan-id 3830;
    family inet {
        address 10.237.18.29/31;
    }
    family mpls;
}

bdale at elow-core-01# run monitor traffic interface ge-1/1/5 layer2-headers matching "ether dst 01:80:c2:00:00:0e"
verbose output suppressed, use <detail> or <extensive> for full protocol decode
Address resolution is ON. Use <no-resolve> to avoid any reverse lookup delay.
Address resolution timeout is 4s.
Listening on ge-1/1/5, capture size 96 bytes

13:36:12.180818 Out 5c:5e:ab:0e:7f:15 > 01:80:c2:00:00:0e, ethertype LLDP (0x88cc), length 68: LLDP, name elow-core-01, length 54
	[|LLDP]