Cisco IOS XR :: "show lldp neighbors" shows [DISABLED] for bundled int

[petehummon]

Hi everyone,

   I'm looking at a production router running Cisco IOS XR Software, Version 7.4.15.  When I do a "show lldp neighbors" for a specific physical interface, I see this:

RP/0/RP0/CPU0:RouterX#show lldp neighbors HundredGigE0/0/0/0
Thu Feb 23 15:20:54.898 EST
Capability codes:
(R) Router, (B) Bridge, (T) Telephone, (C) DOCSIS Cable Device
(W) WLAN Access Point, (P) Repeater, (S) Station, (O) Other

Device ID      Local Intf         Hold-time Capability Port ID
[DISABLED]     HundredGigE0/0/0/0 48        N/A        0123.4567.89ab
RemoteDevice01 HundredGigE0/0/0/0 120       B,R        0123.4567.89ab

Total entries displayed: 2

RP/0/RP0/CPU0:RouterX#

It looks like there are somehow two devices on the other end of this local connection; one device that has turned LLDP off, and another device ("RemoteDevice01") that has it turned on.  The LLDP chassis ID on both devices is identical.  I'm scratching my head, wondering how that might be?  I do not have access to RemoteDevice01.

One thing I do notice on my router is that this physical interface is the (only) member of a Bundle-Ethernet interface:

RP/0/RP0/CPU0:RouterX#show running-config interface HundredGigE0/0/0/0
Thu Feb 23 15:37:15.929 EST
interface HundredGigE0/0/0/0
description "To RemoteDevice01"
bundle id 123 mode on
load-interval 30
!

RP/0/RP0/CPU0:RouterX#show running-config interface bundle-ether 123
Thu Feb 23 15:37:32.096 EST
interface Bundle-Ether123
description "To RemoteDevice01"
mtu 9160
lacp system mac 0000.0000.0001
load-interval 30
dampening
logging events link-status
!

RP/0/RP0/CPU0:RouterX#

Do you think it is likely that on RemoteDevice01, that box has LLDP disabled on its physical interface, but enabled on its bundle interface?  Or vice-versa?  This is the best theory I can devise...

Thank you,  -P

[M02@rt37 · Accepted solution]

Hello @petehummon 

In your case, it seems that the physical interface (HundredGigE0/0/0/0) is a member of a bundle interface (Bundle-Ether123), and LLDP is enabled on the bundle interface but disabled on the physical interface. This would explain why you are seeing two entries for the same chassis ID on your router's LLDP table - one with no device ID (because LLDP is disabled on the physical interface) and one with the device ID of RemoteDevice01 (because LLDP is enabled on the bundle interface).

To confirm this theory, you could try running the "show running-config interface" command on RemoteDevice01 to see if LLDP is indeed enabled on the bundle interface but disabled on the physical interface.

[petehummon]

Yes, you are correct!  I contacted the admin of the remote machine, and indeed, LLDP is disabled on the phy interface, enabled on the bundle.  It looks weird, but makes sense in context...  Thank you

[M02@rt37]

@petehummon