Hi Nicholas, I have tested that 'switchport mode access' + 'switchport nonegotiate' is equivalent to 'switchport mode access' only. Switch ports configured with both combinations of commands do not send DTP packets, as proven using the 'debug dtp packets' privileged command on both Catalyst 2950 and Catalyst 3560 series switches. Below are some captures during my DTP studies. Thanks.
TOS - Trunk Operational Status TAS - Trunk Administrative Status TNS - Trunk Negotiated Status TOT - Trunk Operational Trunking Encapsulation TAT - Trunk Administrative Trunking Encapsulation TNT - Trunk Negotiated Trunking Encapsulation ================================================================================ C3560 dynamic auto <> C3560 dynamic auto C3560#sh int fa0/1 switchport | in Administrative Mode|Administrative Trunking|Negotiation Administrative Mode: dynamic auto Administrative Trunking Encapsulation: negotiate Negotiation of Trunking: On C3560# C3560#sh dtp int fa0/1 | in TOS|TOT TOS/TAS/TNS: ACCESS/AUTO/ACCESS TOT/TAT/TNT: NATIVE/NEGOTIATE/NATIVE 0 bad TLVs, 0 bad TAS, 0 bad TAT, 0 bad TOT, 0 other C3560# ================================================================================ C3560 dynamic auto <> C2950 dynamic desirable C3560#sh int fa0/1 switchport | in Administrative Mode|Administrative Trunking|Negotiation Administrative Mode: dynamic auto Administrative Trunking Encapsulation: negotiate Negotiation of Trunking: On C3560# C3560#sh dtp int fa0/1 | in TOS|TOT TOS/TAS/TNS: TRUNK/AUTO/TRUNK TOT/TAT/TNT: 802.1Q/NEGOTIATE/802.1Q 0 bad TLVs, 0 bad TAS, 0 bad TAT, 0 bad TOT, 0 other C3560# ================================================================================ C3560 dynamic auto <> Cisco 2600 C3560#sh int fa0/1 switchport | in Administrative Mode|Administrative Trunking|Negotiation Administrative Mode: dynamic auto Administrative Trunking Encapsulation: negotiate Negotiation of Trunking: On C3560# C3560#sh dtp int fa0/1 | in TOS|TOT TOS/TAS/TNS: ACCESS/AUTO/ACCESS TOT/TAT/TNT: NATIVE/NEGOTIATE/NATIVE 0 bad TLVs, 0 bad TAS, 0 bad TAT, 0 bad TOT, 0 other C3560# ================================================================================ C3560 dynamic desirable <> C3560 dynamic auto C3560#sh int fa0/1 switchport | in Administrative Mode|Administrative Trunking|Negotiation Administrative Mode: dynamic desirable Administrative Trunking Encapsulation: negotiate Negotiation of Trunking: On C3560# C3560#sh dtp int fa0/1 | in TOS|TOT TOS/TAS/TNS: TRUNK/DESIRABLE/TRUNK TOT/TAT/TNT: ISL/NEGOTIATE/ISL 0 bad TLVs, 0 bad TAS, 0 bad TAT, 0 bad TOT, 0 other C3560# ================================================================================ C3560 switchport trunk encapsulation dot1q, switchport mode trunk <> C3560 dynamic auto C3560#sh int fa0/1 switchport | in Administrative Mode|Administrative Trunking|Negotiation Administrative Mode: trunk Administrative Trunking Encapsulation: dot1q Negotiation of Trunking: On C3560# C3560#sh dtp int fa0/1 | in TOS|TOT TOS/TAS/TNS: TRUNK/ON/TRUNK TOT/TAT/TNT: 802.1Q/802.1Q/802.1Q 0 bad TLVs, 0 bad TAS, 0 bad TAT, 0 bad TOT, 0 other C3560# ================================================================================ C3560 switchport trunk encapsulation dot1q, switchport mode trunk, switchport nonegotiate <> C3560 dynamic auto C3560#sh int fa0/1 switchport | in Administrative Mode|Administrative Trunking|Negotiation Administrative Mode: trunk Administrative Trunking Encapsulation: dot1q Negotiation of Trunking: Off C3560# C3560#sh dtp int fa0/1 | in TOS|TOT TOS/TAS/TNS: TRUNK/NONEGOTIATE/TRUNK TOT/TAT/TNT: 802.1Q/802.1Q/802.1Q 0 bad TLVs, 0 bad TAS, 0 bad TAT, 0 bad TOT, 0 other C3560# ================================================================================ C3560 switchport mode access <> C3560 switchport mode access C3560#sh int fa0/1 switchport | in Administrative Mode|Administrative Trunking|Negotiation Administrative Mode: static access Administrative Trunking Encapsulation: negotiate Negotiation of Trunking: Off C3560# C3560#sh dtp int fa0/1 | in TOS|TOT TOS/TAS/TNS: ACCESS/OFF/ACCESS TOT/TAT/TNT: UNKNOWN/NEGOTIATE/UNKNOWN 0 bad TLVs, 0 bad TAS, 0 bad TAT, 0 bad TOT, 0 other C3560# regards, YapCH http://itcertguides.blogspot.com/ > Message: 3 > Date: Tue, 18 Jan 2011 13:15:49 +0100 > From: Nicolas MICHEL > To: OSL Routing and Switching > Subject: [OSL | CCIE_RS] DTP for Dummies > Message-ID: > > Content-Type: text/plain; charset=ISO-8859-1 > > Hey there. > > > DTP is such an easy protocol . There are only few commands to enable or > disable it. > I've been reading so much crap about this since my CCNA on cisco forums that > I d like to discuss about it with you guys. > > > Some people says that DTP can only be shutted with the command switchport > nonegotiage. > Some people says that DTP can only be shutted with the command switchport > mode access .... > > > I disagree and I noticed that switchport mode access did indeed shut the DTP > process .... > > Rack1SW1(config-if)#do sh int fa0/21 sw > Name: Fa0/21 > Switchport: Enabled > Administrative Mode: static access > Operational Mode: static access > Administrative Trunking Encapsulation: dot1q > Operational Trunking Encapsulation: native > *Negotiation of Trunking: Off* > Access Mode VLAN: 1 (default) > Trunking Native Mode VLAN: 146 (VLAN0146) > Administrative Native VLAN tagging: enabled > Voice VLAN: none > Administrative private-vlan host-association: none > Administrative private-vlan mapping: none > Administrative private-vlan trunk native VLAN: none > Administrative private-vlan trunk Native VLAN tagging: enabled > Administrative private-vlan trunk encapsulation: dot1q > Administrative private-vlan trunk normal VLANs: none > Administrative private-vlan trunk associations: none > Administrative private-vlan trunk mappings: none > Operational private-vlan: none > Trunking VLANs Enabled: ALL > Pruning VLANs Enabled: 2-1001 > Capture Mode Disabled > > > > So what do you guys think about this newbie question ? :) > > > -- > Nicolas MICHEL > Ingenieur R?seaux et Securit? (CCNA/CCNP) > _______________________________________________ For more information regarding industry leading CCIE Lab training, please visit www.ipexpert.com
