My switch won't ping my server. Both are directly connected with each other, and are in vlan 666.

When I initiate a ping from my switch to my server, the switch sends ARP requests. Then the server replies, and the switch adds the mac address in its mac address-table. But after that, it simply does not send a ping. I do not see them on my port monitor capture.

When I initiate from the server to the switch, the switch never replies back to the ARP requests. I have tried adding the entry manually, but then I simply never receive any ICMP echo response.

It should be noted that I can successfully ping another server from my switch.

What can be causing this ? Here is the configuration of the physical port connected to my server:

9300_1#sho run int ten1/1/1

interface TenGigabitEthernet1/1/1
 description To DNA enp9s0
 switchport access vlan 666
 switchport mode access

9300_1#sho run int vl666
interface Vlan666
 ip address

My switch is a Catalyst 9300 Cisco IOS XE Software, Version 16.09.02.

  • 1
    Please include the full switch configuration and the evidence you have of what is happening. – Ron Maupin Dec 17 '18 at 18:00
  • Possible duplicate address? – Ron Trunk Dec 17 '18 at 18:12
  • 1
    Is your ping coming from interface Vlan666? – Ricky Beam Dec 17 '18 at 18:32
  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you can provide and accept your own answer. – Ron Maupin Dec 25 '18 at 10:26

you might want to install a packet capture utility on your server like Wireshark, just to verify that the ping request from the switch is reaching the server. Try running the ping from the switch and check on the servers ARP cache for the MAC address of the switch' SVI. Some possible issues:

 1. unidirectional cables
 2. duplicate IPs
 3. host firewall that blocks ICMP on the server eg. Windows Firewall/IPtables on Linux.
  • Where "host firewall" is the most probable cause in the real world. In that case, it is enough to look at the switch's or router's ARP cache (as in show ip arp vlan 666) to see if ARP resolution was successful. If there is a valid MAC<->IP mapping on the switch/router, then the cause for the missing ping reply is on the server side. If there is no valid MAC<->IP mapping (ARP entry is incomplete for a few seconds), then it's time to investigate layer 1 (cabling ok?) and layer 2 (VLAN ok?) to/from that server. – Marc 'netztier' Luethi Jan 20 '19 at 16:27

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