On Wed, 9 Jul 2014 10:33:25 -0300 Bruno Galindro da Costa <bruno.galindro@gmail.com> wrote:

> I've two switches: xxx.xxx.251.245 and xxx.xxx.252.121.
>
> 250.121 is connected to GigabitEthernet 1/0/5 of 251.245
> 251.245 is connected to GigabitEthernet 1/48 of 250.121

You are referring to three different addresses here, not two, which is a
bit confusing. I'm going to assume that whenever you wrote 250.121,
what you really meant was 252.121.

> 251.245 is a 5500G-EI 24-Port (3Com Switch 5500G-EI 24-Port Software
> Version 3Com OS V3.03.02s168p22 from 3com)
> 250.121 is a DGS-3120-48TC (DGS-3120-48TC Gigabit Ethernet Switch from
> dlink)
>
> All of them has LLDP enabled.
>
> This is the neighbor information on switch port 1/48 of 250.121:
>
> Port ID : 1:48
> -------------------------------------------------------------------------------
> Remote Entities Count : 1
> Entity 1
>     Chassis ID Subtype                         : MAC Address
>     Chassis ID                                 : 00-1E-C1-ED-78-80

So 251.245 has identified itself to 252.121 by its MAC address
00-1E-C1-ED-78-80.

> This is the neighbor information on switch port 1/0/5 of 251.245:
>
> LLDP neighbor-information of port 5[GigabitEthernet1/0/5]:
>   Neighbor index   : 1
>   Update time      : 80 days,21 hours,14 minutes,30 seconds
>   Chassis type     : MAC address
>   Chassis ID       : 2810-7B68-9D90

While 252.121 has identified itself to 251.245 by its MAC address
2810-7B68-9D90.


It appears to me that NAV is failing to see that 00-1E-C1-ED-78-80 is in
fact the device 251.245, which is why you are seeing this record in the
"unrecognized neighbors" list for 252.121:1/48.

NAV doesn't use the lldpRemManAddrTable to get management information
for remote devices. When a remote device identifies itself with a MAC
address like this, NAV will try to look up known MAC addresses from its
own database.

It will look at ARP data. If 251.245 has never communicated over IP
using the 00-1E-C1-ED-78-80 address, there will be no ARP data to find.

Secondly, NAV will look at the known physical addresses of any known
interface. If has collected no interfaces from 251.245 with the physical
address 00-1E-C1-ED-78-80, there will be no data found.

At this point, NAV has failed to identify the neighbor and puts it in
the unrecognized neigbors list. The only identified neighbor candidates
end up coming from CAM data, which can be an unreliable source.

-

So, my question is: If you search for 00-1E-C1-ED-78-80 in the Machine
Tracker, do you have any hits for 251.245? If you look at the complete
interface report for 251.245, do you see any interfaces with this adress
in the physical address column?

Conversely, can you find machine tracker records linking
28-10-7B-68-9D-90 to the 252.121 IP address, or any interfaces on
252.121 with this physical address?


If not, NAV may need to employ further strategies to identify MAC
addresses on devices.


--
Morten Brekkevold
UNINETT