Clients lose connectivity

[gary_the_network_guy]

Some Clients lose connectivity for no apparent reason, they get an ip address but then they have connectivity issues.

I cannot explain it, at frst it seemed it loses connectivity when put into another vlan, but it seems it is a not vlan related issue.

Somehow my switch does not learn mac-addresses on the connected ports.

[balaji.bandi]

what switch model, what VLAN you lost connection ? (what Logs you see on the switch)

how is your network ? ( any spanning tree issue ?)

show version

show run

show vlan

show log

will help, also if you have any small network diagram also help to understand.

[Flavio Miranda]

Hi

 Start by checking the physical layer. Make sure cabling is OK, make sure the interface is going up properly.  Then, look at the configuration. ARe you using some security feature?  Port-security can be a problem if you change machines from port to another.

Better yet, share the config here.

[gary_the_network_guy]

We are not using any security-features. We have a collapsed core architecture, with a simple Core/Distribution - Access Design.

Core: WS-C4500X-32 Version: 15.2

Access: C9200-48P Version 16.2

core - access -client

vlan configuration is 

interface Vlan140
ip address 10.xxx 255.255.252.0
ip helper-address 10.xxx
ip helper-address 10.xxx
ip helper-address 10.xxx

[balaji.bandi]

what is the logs you see on both the switches ? when you lost the connection ?

C9200-48P Version 16.2  - this quite OLD version, uplist to 17.3.3 or higher when you get chance.

[Flavio Miranda]

Any security feature on the machine side?  Did you tested with more then one device and operational system?

[Leo Laohoo]

---

@gary_the_network_guy wrote:

Core: WS-C4500X-32 Version: 15.2

Access: C9200-48P Version 16.2

---

Give us the exact IOS version number or do not even bother.  

9200 running on 16.2?  Not remotely possible because Catalyst 9200 does not support IOS-XE version 16.2.X.  

[Elliot Dierksen]

You are using a /22 according to the interface you listed. How many switches in your environment? That is a big network to spread out across a bunch of switches. Nothing but gut feel, but I bet you are having spanning tree issues. It probably isn't that things are getting dropped. It is probably a TCN (topology change notification) that is causing your switches to flood traffic. Look at something like this.

EBD-3750E#sh spanning-tree vlan 3 detail

 VLAN0003 is executing the rstp compatible Spanning Tree protocol
  Bridge Identifier has priority 4096, sysid 3, address 0024.c45a.6900
  Configured hello time 2, max age 20, forward delay 15, transmit hold-count 6
  We are the root of the spanning tree
  Topology change flag not set, detected flag not set
  Number of topology changes 122 last change occurred 1d18h ago
          from Port-channel31
  Times:  hold 1, topology change 35, notification 2
          hello 2, max age 20, forward delay 15
  Timers: hello 0, topology change 0, notification 0, aging 300

In your case you would use VLAN 140. See when the last topology change happened.

[gary_the_network_guy]

So connectivity is now given, but I still do not learn mac-addresses on the access-switch. I think there is something wrong with the access-switch. Connectivitty was resotered somehow our dhcp was faulty, dhcp-option router was missing.

[MHM Cisco World]

https://bst.cisco.com/bugsearch/bug/CSCvt22238

I think this is bug check link.