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dtp negotiation breaks APs poe from the sw

tommar
Level 1
Level 1

hello heros,  dtp is disabled by "switchport nonego" but still i see 


Sep 19 21:16:37.541: %DTP-5-NONTRUNKPORTON: Port Gi3/0/23 has become non-trunk
Sep 19 21:16:38.027: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet3/0/23, changed state to down
Sep 19 21:16:39.042: %LINK-3-UPDOWN: Interface GigabitEthernet3/0/23, changed state to down
Sep 19 21:16:40.052: %DTP-5-TRUNKPORTON: Port Gi3/0/23 has become dot1q trunk
Sep 19 21:16:41.552: %LINK-3-UPDOWN: Interface GigabitEthernet3/0/23, changed state to up

this causes the attached AP to lose power and reboot. i ve already removed switchport access vlan XXY so the dtp should not work but still it does. 


interface GigabitEthernet3/0/23
switchport mode trunk
switchport nonegotiate

 

ASW1#sh dtp int GigabitEthernet3/0/23
DTP information for GigabitEthernet3/0/23:
TOS/TAS/TNS: TRUNK/NONEGOTIATE/TRUNK
TOT/TAT/TNT: 802.1Q/802.1Q/802.1Q
Neighbor address 1: 000000000000
Neighbor address 2: 000000000000
Hello timer expiration (sec/state): never/STOPPED
Access timer expiration (sec/state): never/STOPPED
Negotiation timer expiration (sec/state): never/STOPPED
Multidrop timer expiration (sec/state): never/STOPPED
FSM state: S6:TRUNK
# times multi & trunk 0
Enabled: yes    <<<<<<<<< !

 

i need to stop the AP from loosing power or/and the dtp to run.  ideas?

4 Replies 4

balaji.bandi
Hall of Fame
Hall of Fame

why do you need AP port as Trunk ? if you configured access port DTP will not be trouble you.

DTP from my notes :

switchport mode trunk says: “Always trunk on this end, and I will send DTP to attempt to negotiate a trunk on the other end.”

switchport nonegotiate says: “Do not send or respond to DTP from this end. Disable all DTP on this port.”

switchport mode dynamic desirable says: “Ask the other end to trunk using DTP and trunk if the negotiation succeeds. If DTP negotiation fails then become an access port.”

switchport mode dynamic auto says: “If the other end asks me to be a trunk with DTP, then become a trunk, but I wont initiate any negotitation from this end. If no one asks me to become a trunk then I will become an access port.”

switchport mode access says: “Never trunk on this end and never send DTP messages"

switchport trunk encapsulation says: “Do not negotiate the trunk protocol with DTP. Only use the trunk protocol specified in this command (isl or dot1q).

 

 

BB

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the AP actually serves more vlans/ssids that need to be separate, thats why i need it trunk. 

Hello,

I wonder if DTP is actually the problem. What Cisco switch and what APs do you have ? Things like PoE could be the problem as well (as described in the thread below)...

https://community.ui.com/questions/UniFi-XG-AP-Dropping-Connection/9efd121c-13ad-4c8f-bc74-5a185646fb73?page=1

thanks Mr. Georg, good point, definitely plenty of power is on the switch to be granted. there are just 4 APs on the C3850-48P, each takes like 15w and still >160w remaining.

 

ASW1#show power inline

Module Available Used Remaining
(Watts) (Watts) (Watts)
------ --------- -------- ---------
1 405.0 166.8 238.2


Interface Admin Oper Power Device Class Max
(Watts)
--------- ------ ---------- ------- ------------------- ----- ----
Gi1/0/46 auto on 15.4 AIR-CAP3602I-E-K9 4 30.0

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