S2#show run
Building configuration...

Current configuration : 2651 bytes
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! Last configuration change at 14:37:51 UTC Mon Jan 19 2026
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version 15.2
no service pad
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
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hostname S2
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boot-start-marker
boot-end-marker
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no aaa new-model
switch 1 provision c1000-24t-4g-l
system mtu routing 1500
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spanning-tree mode rapid-pvst
spanning-tree extend system-id
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vlan internal allocation policy ascending
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interface Port-channel1
 switchport trunk allowed vlan 10,20,30,99
 switchport trunk native vlan 99
 switchport mode trunk
 switchport nonegotiate
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interface GigabitEthernet1/0/1
 switchport trunk allowed vlan 10,20,30,99
 switchport trunk native vlan 99
 switchport mode trunk
 switchport nonegotiate
 channel-protocol pagp
 channel-group 1 mode desirable
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interface GigabitEthernet1/0/2
 switchport trunk allowed vlan 10,20,30,99
 switchport trunk native vlan 99
 switchport mode trunk
 switchport nonegotiate
 channel-protocol pagp
 channel-group 1 mode desirable
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interface GigabitEthernet1/0/3
 switchport access vlan 10
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interface GigabitEthernet1/0/4
 switchport access vlan 10
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interface GigabitEthernet1/0/5
 switchport access vlan 10
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interface GigabitEthernet1/0/6
 switchport access vlan 10
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interface GigabitEthernet1/0/7
 switchport access vlan 10
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interface GigabitEthernet1/0/8
 switchport access vlan 10
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interface GigabitEthernet1/0/9
 switchport access vlan 10
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interface GigabitEthernet1/0/10
 switchport access vlan 10
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interface GigabitEthernet1/0/11
 switchport access vlan 10
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interface GigabitEthernet1/0/12
 switchport access vlan 20
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interface GigabitEthernet1/0/13
 switchport access vlan 20
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interface GigabitEthernet1/0/14
 switchport access vlan 20
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interface GigabitEthernet1/0/15
 switchport access vlan 20
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interface GigabitEthernet1/0/16
 switchport access vlan 20
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interface GigabitEthernet1/0/17
 switchport access vlan 20
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interface GigabitEthernet1/0/18
 switchport access vlan 20
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interface GigabitEthernet1/0/19
 switchport access vlan 30
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interface GigabitEthernet1/0/20
 switchport access vlan 30
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interface GigabitEthernet1/0/21
 switchport access vlan 30
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interface GigabitEthernet1/0/22
 switchport access vlan 30
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interface GigabitEthernet1/0/23
 switchport access vlan 30
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interface GigabitEthernet1/0/24
 switchport access vlan 30
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interface GigabitEthernet1/0/25
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interface GigabitEthernet1/0/26
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interface GigabitEthernet1/0/27
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interface GigabitEthernet1/0/28
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interface Vlan1
 no ip address
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interface Vlan20
 no ip address
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ip http server
ip http secure-server
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line con 0
line vty 5 15
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end

S2#
*Jan 19 15:38:48.316: %LINK-3-UPDOWN: Interface GigabitEthernet1/0/1, changed state to up
*Jan 19 15:38:48.616: %LINK-3-UPDOWN: Interface GigabitEthernet1/0/2, changed state to up
*Jan 19 15:38:55.944: %CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered on GigabitEthernet1/0/1 (99), with Switch GigabitEthernet1/0/1 (1).
*Jan 19 15:38:55.944: %CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered on GigabitEthernet1/0/2 (99), with Switch GigabitEthernet1/0/2 (1).
*Jan 19 15:38:56.544: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet1/0/2, changed state to up
*Jan 19 15:38:56.615: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet1/0/1, changed state to up
*Jan 19 15:38:56.943: %CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered on GigabitEthernet1/0/1 (99), with Switch GigabitEthernet1/0/1 (1).
*Jan 19 15:38:56.943: %CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered on GigabitEthernet1/0/2 (99), with Switch GigabitEthernet1/0/2 (1).
*Jan 19 15:38:57.945: %CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered on GigabitEthernet1/0/1 (99), with Switch GigabitEthernet1/0/1 (1).
*Jan 19 15:38:57.945: %CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered on GigabitEthernet1/0/2 (99), with Switch GigabitEthernet1/0/2 (1).
*Jan 19 15:38:58.944: %CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered on GigabitEthernet1/0/1 (99), with Switch GigabitEthernet1/0/1 (1).
*Jan 19 15:38:58.945: %CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered on GigabitEthernet1/0/2 (99), with Switch GigabitEthernet1/0/2 (1).
S2#
*Jan 19 15:38:59.944: %CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered on GigabitEthernet1/0/1 (99), with Switch GigabitEthernet1/0/1 (1).
*Jan 19 15:38:59.945: %CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered on GigabitEthernet1/0/2 (99), with Switch GigabitEthernet1/0/2 (1).show ip int brief
Interface              IP-Address      OK? Method Status                Protocol
Vlan1                  unassigned      YES unset  up                    down
Vlan20                 unassigned      YES unset  up                    up
GigabitEthernet1/0/1   unassigned      YES unset  up                    up
GigabitEthernet1/0/2   unassigned      YES unset  up                    up
GigabitEthernet1/0/3   unassigned      YES unset  down                  down
GigabitEthernet1/0/4   unassigned      YES unset  down                  down
GigabitEthernet1/0/5   unassigned      YES unset  down                  down
GigabitEthernet1/0/6   unassigned      YES unset  down                  down
GigabitEthernet1/0/7   unassigned      YES unset  down                  down
GigabitEthernet1/0/8   unassigned      YES unset  down                  down
GigabitEthernet1/0/9   unassigned      YES unset  down                  down
GigabitEthernet1/0/10  unassigned      YES unset  down                  down
GigabitEthernet1/0/11  unassigned      YES unset  down                  down
GigabitEthernet1/0/12  unassigned      YES unset  up                    up
GigabitEthernet1/0/13  unassigned      YES unset  down                  down
GigabitEthernet1/0/14  unassigned      YES unset  down                  down
GigabitEthernet1/0/15  unassigned      YES unset  down                  down
GigabitEthernet1/0/16  unassigned      YES unset  down                  down
GigabitEthernet1/0/17  unassigned      YES unset  down                  down
GigabitEthernet1/0/18  unassigned      YES unset  down                  down
GigabitEthernet1/0/19  unassigned      YES unset  down                  down
GigabitEthernet1/0/20  unassigned      YES unset  down                  down
GigabitEthernet1/0/21  unassigned      YES unset  down                  down
GigabitEthernet1/0/22  unassigned      YES unset  down                  down
GigabitEthernet1/0/23  unassigned      YES unset  down                  down
GigabitEthernet1/0/24  unassigned      YES unset  down                  down
GigabitEthernet1/0/25  unassigned      YES unset  down                  down
GigabitEthernet1/0/26  unassigned      YES unset  down                  down
GigabitEthernet1/0/27  unassigned      YES unset  down                  down
GigabitEthernet1/0/28  unassigned      YES unset  down                  down
Port-channel1          unassigned      YES unset  down                  down

S2#
*Jan 19 15:39:26.322: %SW_MATM-4-MACFLAP_NOTIF: Host c46e.1f06.1741 in vlan 99 is flapping between port Gi1/0/1 and port Gi1/0/2
*Jan 19 15:39:29.571: %SW_MATM-4-MACFLAP_NOTIF: Host c46e.1f06.1741 in vlan 99 is flapping between port Gi1/0/2 and port Gi1/0/1show ether
*Jan 19 15:39:34.853: %SW_MATM-4-MACFLAP_NOTIF: Host e438.7e91.9741 in vlan 99 is flapping between port Gi1/0/1 and port Gi1/0/2channel summary
Flags:  D - down        P - bundled in port-channel
        I - stand-alone s - suspended
        H - Hot-standby (LACP only)
        R - Layer3      S - Layer2
        U - in use      N - not in use, no aggregation
        f - failed to allocate aggregator

        M - not in use, minimum links not met
        m - not in use, port not aggregated due to minimum links not met
        u - unsuitable for bundling
        w - waiting to be aggregated
        d - default port

        A - formed by Auto LAG


Number of channel-groups in use: 1
Number of aggregators:           1

Group  Port-channel  Protocol    Ports
------+-------------+-----------+-----------------------------------------------
1      Po1(SD)         PAgP      Gi1/0/1(I)  Gi1/0/2(I)


S2#
*Jan 19 15:39:51.969: %CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered on GigabitEthernet1/0/2 (99), with Switch GigabitEthernet1/0/2 (1).show vlan brief

VLAN Name                             Status    Ports
---- -------------------------------- --------- -------------------------------
1    default                          active    Gi1/0/25, Gi1/0/26, Gi1/0/27
                                                Gi1/0/28
10   Academics                        active    Gi1/0/3, Gi1/0/4, Gi1/0/5
                                                Gi1/0/6, Gi1/0/7, Gi1/0/8
                                                Gi1/0/9, Gi1/0/10, Gi1/0/11
20   Stude
*Jan 19 15:39:53.450: %CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered on GigabitEthernet1/0/1 (99), with Switch GigabitEthernet1/0/1 (1).nts                         active    Gi1/0/12, Gi1/0/13, Gi1/0/14
                                                Gi1/0/15, Gi1/0/16, Gi1/0/17
                                                Gi1/0/18
30   Guests                           active    Gi1/0/19, Gi1/0/20, Gi1/0/21
                                                Gi1/0/22, Gi1/0/23, Gi1/0/24
99   Management/Native                active
1002 fddi-default                     act/unsup
1003 token-ring-default               act/unsup
1004 fddinet-default                  act/unsup
1005 trnet-default                    act/unsup

show interfaces trunk
Port        Mode             Encapsulation  Status        Native vlan
Gi1/0/1     on               802.1q         trunking      99
Gi1/0/2     on               802.1q         trunking      99

Port        Vlans allowed on trunk
Gi1/0/1     10,20,30,99
Gi1/0/2     10,20,30,99

Port        Vlans allowed and active in management domain
Gi1/0/1     10,20,30,99
Gi1/0/2     10,20,30,99

Port        Vlans in spanning tree forwarding state and not pruned
Gi1/0/1     10,20,30,99
Gi1/0/2     10,20,30,99



