CDP acts weird - Page 2

OLE DREWS JENSEN · ‎06-18-2023

I have 3 Cisco Catalyst 2960S switches on a mesh network: A (host), B and C.

If I do a sh cdp nei on switch A, I can see B and C.

If I do a sh cdp nei on switch B, I can only see C, and on C I can only see B.

I can ping all from all.

What could be the reason for this?

Thanks,

Ole

OLE DREWS JENSEN · ‎06-18-2023

Thanks.

Tried this command on both A and B and while it confirms the command and tells me debugging is on, nothing shows afterwards.

MHM Cisco World · ‎06-18-2023

Can I see show cdp neighbor in SW-A

OLE DREWS JENSEN · ‎06-18-2023

Sure.

Note I have 2 switches named SE-Switch. First is the 2960 (switch D) on "old" mesh connected to port 19, and second is 2960S (switch C) on "new" mesh connected on port 48. I know that's not a nice solution, and I will rename the one on the old mesh. Also, for some reason, a bunch of my VoIP phones are showing.

GE-Switch-1#sh cdp nei
Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
S - Switch, H - Host, I - IGMP, r - Repeater, P - Phone,
D - Remote, C - CVTA, M - Two-port Mac Relay

Device ID Local Intrfce Holdtme Capability Platform Port ID
SE-Switch Gig 1/0/19 133 S I WS-C2960- Fas 0/47
SEP482567099d18 Gig 1/0/19 156 H P Polycom V Port 1
SEP64167fb6b0fc Gig 1/0/12 149 H P Polycom V Port 1
SEP64167fe747a6 Gig 1/0/25 134 H P Polycom V Port 1
SEP64167fb64b42 Gig 1/0/41 153 H P Polycom V Port 1
SEP64167fb68d20 Gig 1/0/40 176 H P Polycom V Port 1
SEP64167fe73d87 Gig 1/0/45 164 H P Polycom V Port 1
SEP482567099ccd Gig 1/0/19 175 H P Polycom V Port 1
SEP482567099c67 Gig 1/0/19 130 H P Polycom V Port 1
SEP482567099bee Gig 1/0/19 141 H P Polycom V Port 1
SE-SWITCH Gig 1/0/48 128 S I WS-C2960S Gig 1/0/24
SEP64167fb67d0b Gig 1/0/9 130 H P Polycom V Port 1
SEP64167fe73c8a Gig 1/0/42 120 H P Polycom V Port 1
SEP64167fb68047 Gig 1/0/10 158 H P Polycom V Port 1
SEP482567099cd5 Gig 1/0/19 146 H P Polycom V Port 1
SEP482567099d3e Gig 1/0/19 173 H P Polycom V Port 1
ec1d8bef1a70 Gig 1/0/19 125 S I SG200-26 gi26
RWR-3548-1 Gig 1/0/47 158 T S WS-C3548- Gig 0/1
SWC-SWITCH Gig 1/0/48 164 S I WS-C2960S Gig 1/0/24
GE-Switch-1#

MHM Cisco World · ‎06-18-2023

Show cdp traffic

Show cdp interface

Please share above

OLE DREWS JENSEN · ‎06-18-2023

GE-Switch-1#sh cdp tra
CDP counters :
Total packets output: 13567741, Input: 8631504
Hdr syntax: 0, Chksum error: 0, Encaps failed: 0
No memory: 0, Invalid packet: 0,
CDP version 1 advertisements output: 0, Input: 0
CDP version 2 advertisements output: 13567741, Input: 8631504

GE-Switch-1#sh cdp int
FastEthernet0 is down, line protocol is down
Encapsulation ARPA
Sending CDP packets every 15 seconds
Holdtime is 180 seconds
GigabitEthernet1/0/1 is up, line protocol is up
Encapsulation ARPA
Sending CDP packets every 15 seconds
Holdtime is 180 seconds
GigabitEthernet1/0/2 is up, line protocol is up
Encapsulation ARPA
Sending CDP packets every 15 seconds
Holdtime is 180 seconds
GigabitEthernet1/0/3 is down, line protocol is down
Encapsulation ARPA
Sending CDP packets every 15 seconds
Holdtime is 180 seconds
GigabitEthernet1/0/4 is up, line protocol is up
Encapsulation ARPA
Sending CDP packets every 15 seconds
Holdtime is 180 seconds
GigabitEthernet1/0/5 is up, line protocol is up
Encapsulation ARPA
Sending CDP packets every 15 seconds
Holdtime is 180 seconds
GigabitEthernet1/0/6 is down, line protocol is down
Encapsulation ARPA
Sending CDP packets every 15 seconds
Holdtime is 180 seconds
GigabitEthernet1/0/7 is up, line protocol is up
Encapsulation ARPA
Sending CDP packets every 15 seconds
Holdtime is 180 seconds
GigabitEthernet1/0/8 is up, line protocol is up
Encapsulation ARPA
Sending CDP packets every 15 seconds
Holdtime is 180 seconds
GigabitEthernet1/0/9 is up, line protocol is up
Encapsulation ARPA
Sending CDP packets every 15 seconds
Holdtime is 180 seconds
GigabitEthernet1/0/10 is up, line protocol is up
Encapsulation ARPA
Sending CDP packets every 15 seconds
Holdtime is 180 seconds
GigabitEthernet1/0/11 is up, line protocol is up
Encapsulation ARPA
Sending CDP packets every 15 seconds
Holdtime is 180 seconds
GigabitEthernet1/0/12 is up, line protocol is up
Encapsulation ARPA
Sending CDP packets every 15 seconds
Holdtime is 180 seconds
GigabitEthernet1/0/13 is up, line protocol is up
Encapsulation ARPA
Sending CDP packets every 15 seconds
Holdtime is 180 seconds
GigabitEthernet1/0/14 is down, line protocol is down
Encapsulation ARPA
Sending CDP packets every 15 seconds
Holdtime is 180 seconds
GigabitEthernet1/0/15 is down, line protocol is down
Encapsulation ARPA
Sending CDP packets every 15 seconds
Holdtime is 180 seconds
GigabitEthernet1/0/16 is down, line protocol is down
Encapsulation ARPA
Sending CDP packets every 15 seconds
Holdtime is 180 seconds
GigabitEthernet1/0/17 is up, line protocol is up
Encapsulation ARPA
Sending CDP packets every 15 seconds
Holdtime is 180 seconds
GigabitEthernet1/0/18 is down, line protocol is down
Encapsulation ARPA
Sending CDP packets every 15 seconds
Holdtime is 180 seconds
GigabitEthernet1/0/19 is up, line protocol is up
Encapsulation ARPA
Sending CDP packets every 15 seconds
Holdtime is 180 seconds
GigabitEthernet1/0/20 is down, line protocol is down
Encapsulation ARPA
Sending CDP packets every 15 seconds
Holdtime is 180 seconds
GigabitEthernet1/0/21 is down, line protocol is down
Encapsulation ARPA
Sending CDP packets every 15 seconds
Holdtime is 180 seconds
GigabitEthernet1/0/22 is down, line protocol is down
Encapsulation ARPA
Sending CDP packets every 15 seconds
Holdtime is 180 seconds
GigabitEthernet1/0/23 is down, line protocol is down
Encapsulation ARPA
Sending CDP packets every 15 seconds
Holdtime is 180 seconds
GigabitEthernet1/0/24 is up, line protocol is up
Encapsulation ARPA
Sending CDP packets every 15 seconds
Holdtime is 180 seconds
GigabitEthernet1/0/25 is up, line protocol is up
Encapsulation ARPA
Sending CDP packets every 15 seconds
Holdtime is 180 seconds
GigabitEthernet1/0/26 is down, line protocol is down
Encapsulation ARPA
Sending CDP packets every 15 seconds
Holdtime is 180 seconds
GigabitEthernet1/0/27 is down, line protocol is down
Encapsulation ARPA
Sending CDP packets every 15 seconds
Holdtime is 180 seconds
GigabitEthernet1/0/28 is down, line protocol is down
Encapsulation ARPA
Sending CDP packets every 15 seconds
Holdtime is 180 seconds
GigabitEthernet1/0/29 is down, line protocol is down
Encapsulation ARPA
Sending CDP packets every 15 seconds
Holdtime is 180 seconds
GigabitEthernet1/0/30 is down, line protocol is down
Encapsulation ARPA
Sending CDP packets every 15 seconds
Holdtime is 180 seconds
GigabitEthernet1/0/31 is down, line protocol is down
Encapsulation ARPA
Sending CDP packets every 15 seconds
Holdtime is 180 seconds
GigabitEthernet1/0/32 is down, line protocol is down
Encapsulation ARPA
Sending CDP packets every 15 seconds
Holdtime is 180 seconds
GigabitEthernet1/0/33 is down, line protocol is down
Encapsulation ARPA
Sending CDP packets every 15 seconds
Holdtime is 180 seconds
GigabitEthernet1/0/34 is down, line protocol is down
Encapsulation ARPA
Sending CDP packets every 15 seconds
Holdtime is 180 seconds
GigabitEthernet1/0/35 is down, line protocol is down
Encapsulation ARPA
Sending CDP packets every 15 seconds
Holdtime is 180 seconds
GigabitEthernet1/0/36 is up, line protocol is up
Encapsulation ARPA
Sending CDP packets every 15 seconds
Holdtime is 180 seconds
GigabitEthernet1/0/37 is down, line protocol is down
Encapsulation ARPA
Sending CDP packets every 15 seconds
Holdtime is 180 seconds
GigabitEthernet1/0/38 is up, line protocol is up
Encapsulation ARPA
Sending CDP packets every 15 seconds
Holdtime is 180 seconds
GigabitEthernet1/0/39 is down, line protocol is down
Encapsulation ARPA
Sending CDP packets every 15 seconds
Holdtime is 180 seconds
GigabitEthernet1/0/40 is up, line protocol is up
Encapsulation ARPA
Sending CDP packets every 15 seconds
Holdtime is 180 seconds
GigabitEthernet1/0/41 is up, line protocol is up
Encapsulation ARPA
Sending CDP packets every 15 seconds
Holdtime is 180 seconds
GigabitEthernet1/0/42 is up, line protocol is up
Encapsulation ARPA
Sending CDP packets every 15 seconds
Holdtime is 180 seconds
GigabitEthernet1/0/43 is up, line protocol is up
Encapsulation ARPA
Sending CDP packets every 15 seconds
Holdtime is 180 seconds
GigabitEthernet1/0/44 is down, line protocol is down
Encapsulation ARPA
Sending CDP packets every 15 seconds
Holdtime is 180 seconds
GigabitEthernet1/0/45 is up, line protocol is up
Encapsulation ARPA
Sending CDP packets every 15 seconds
Holdtime is 180 seconds
GigabitEthernet1/0/46 is down, line protocol is down
Encapsulation ARPA
Sending CDP packets every 15 seconds
Holdtime is 180 seconds
GigabitEthernet1/0/47 is up, line protocol is up
Encapsulation ARPA
Sending CDP packets every 15 seconds
Holdtime is 180 seconds
GigabitEthernet1/0/48 is up, line protocol is up
Encapsulation ARPA
Sending CDP packets every 15 seconds
Holdtime is 180 seconds
GigabitEthernet1/0/49 is down, line protocol is down
Encapsulation ARPA
Sending CDP packets every 15 seconds
Holdtime is 180 seconds
GigabitEthernet1/0/50 is down, line protocol is down
Encapsulation ARPA
Sending CDP packets every 15 seconds
Holdtime is 180 seconds
GigabitEthernet1/0/51 is down, line protocol is down
Encapsulation ARPA
Sending CDP packets every 15 seconds
Holdtime is 180 seconds
GigabitEthernet1/0/52 is down, line protocol is down
Encapsulation ARPA
Sending CDP packets every 15 seconds
Holdtime is 180 seconds
GE-Switch-1#

Richard Burts · ‎06-19-2023

Thanks for the output of show cdp interface. What is Gig 1/0/48 physically connected to?

I wonder about cdp timer 15 in the config. If you remove it does the behavior change?

HTH

Rick

OLE DREWS JENSEN · ‎06-19-2023

1/0/48 is connected to a small media converter which has a fiber connection to our NEW mesh provider for virtual circuits to our branch offices. This is the one where the switch can see the switches at the branch offices, but the branch offices can only see the other branch offices, not this switch.

1/0/19 is connected to another small media converter which has a fiber connection to CURRENT (soon to be OLD) mesh provider for virtual circuits to our branch offices. This switch can see the Cisco switch at a branch office, and the branch office switch can see this switch.

When I use the word "see", I'm referring to "sh cdp nei". All of them can ping each other just fine.

FYI, all are Layer 2 Virtual Circuits, so I can simply plug in the RJ45 they provide to my L2 switches, so it seems all branches are on the same LAN. So, no routing or VLAN tagging is involved for my part.

As to your question about the 15 sec, that was a something I configured yesterday to see if it would help. Default CDP transmissions are every 60 secs (I believe), so I changed it to 15. It has not changed anything, other than those who can see the other neighbors will see them faster after a clear cdp.

Thanks.

MHM Cisco World · ‎06-19-2023

What are the ports connect to SW B and C and sw D

If cdp enable

Then check the service provider taht connect all SW if it allow l2protocol cdp or not.

OLE DREWS JENSEN · ‎06-20-2023

Switch A connects to the mesh with the CDP issues on port G1/0/48.

Switches B and C connects to same mesh on their port G1/0/24.

The mesh provider claim they do NOT block CDP or any other L2 traffic.

Switch A connects to the older mesh with working CDP in both directions on port G1/0/19.

Switch D connects to the older mesh on port G1/0/47.

Below is a better drawing, showing their actual hostnames (A:GE-Switch-1, B:SWC-SWITCH, C:SE-SWITCH, D:SE-2960).

Richard Burts · ‎06-20-2023

Thanks for the additional information. We do not see issues in the posted config. The posted output of show commands does not show any issues. I understand the mesh provider says they are not blocking CDP but based on the information available to us at this point I believe that the most likely explanation of the issue is that something about the mesh is interfering with CDP.

HTH

Rick