From: Mushtaq A. Khan (mak.ccie2b@gmail.com)
Date: Tue Mar 14 2006 - 18:08:20 GMT-3
All,
Can someone explain this to me? SW1 is configured as "switchport
nonegotiate" for port 23 and 24 and I left SW2 with the default
configuration. My question is that why SW1 is showing as "Trunking" even
though SW2 is has no trunk configuration and showing as "Not Trunking"?
SW1#sh run int f1/0/23
interface FastEthernet1/0/23
switchport trunk encapsulation isl
switchport mode trunk
switchport nonegotiate
end
SW1#sh run int f1/0/24
interface FastEthernet1/0/24
switchport trunk encapsulation isl
switchport mode trunk
switchport nonegotiate
end
SW1#sh int trun
Port Mode Encapsulation Status Native vlan
Fa1/0/23 on isl trunking 1
Fa1/0/24 on isl trunking 1
.........
SW2#sh int f1/0/24 tru
Port Mode Encapsulation Status Native vlan
Fa1/0/24 auto negotiate not-trunking 1
SW2#sh int f1/0/23 tru
Port Mode Encapsulation Status Native vlan
Fa1/0/23 auto negotiate not-trunking 1
TIA,
Mushtaq
On 3/13/06, Geert Nijs <geert.nijs@simac.be> wrote:
>
> Mark,
>
> I think CDP gets wacked because one side is access port and the other is
> ISL trunking.
> ISL adds an encapsulation layer around a packet, and i am not sure that
> he does this also for the native vlan.
> I know DOT1Q trunking does not tag on the native vlan, so the other side
> should be able to read the CDP and VTP messages,
> but i am not sure about ISL ?
>
> Easy to check: force the trunking mode on the nonegotiate side to DOT1Q
> and check if cdp gets through. I guess it will.
> Change to ISL trunking and..if it doesn't get through then ISL
> encapsulates even on the native vlan.
>
> Geert
>
> -----Oorspronkelijk bericht-----
> Van: nobody@groupstudy.com [mailto:nobody@groupstudy.com] Namens Mark
> Lasarko
> Verzonden: maandag 13 maart 2006 19:24
> Aan: ccielab@groupstudy.com; rguyler@shp-dayton.org
> Onderwerp: RE: Trunk Modes theory
>
>
> Yes, I had mentioned I was running 12.2(25)SED in my initial response.
> (12.2x on the 3550's in the lab now, right?)
>
> I was simply trying to demonstrate the status:
> non-trunking vs. trunking in my post, using Geert's configs.
>
> Nice info for the group to know; different options in different
> versions, You could read a lot into that (and I am sure many will)
>
> BTW - Anybody know why CDP would also get whacked here?
> (for lack of a better term - it was weird to see, may need to span)
>
> ~M
>
>
> >>> "Guyler, Rik" <rguyler@shp-dayton.org> 03/13/06 12:04 PM >>>
>
> SW1#sh ver
> Cisco Internetwork Operating System Software
> IOS (tm) C3550 Software (C3550-I5Q3L2-M), Version 12.1(22)EA5, RELEASE
> SOFTWARE (fc1)
>
> SW1(config-if)#sw mod ?
> access Set trunking mode to ACCESS unconditionally
> dot1q-tunnel Set trunking mode to DOT1Q TUNNEL unconditionally
> dynamic Set trunking mode to dynamically negotiate access or
> trunk
> mode
> trunk Set trunking mode to TRUNK unconditionally
>
>
> I don't have the "nonegotiate" option but by the description of setting
> it to trunk mode, it appears that no negotiation is taking place since
> it will trunk unconditionally. Does this mean no negotiation or is DTP
> still being output from the switch? I interpret this to mean that the
> trunk is turned on with the configured encapsulation and no DTP is being
> sent over the link but I may be wrong. I didn't hook up a sniffer to
> test it so if anybody can confirm this one way or the other.
>
> Rik
>
>
> ________________________________
>
> From: Mark Lasarko [mailto:mlasarko@co.ba.md.us]
> Sent: Monday, March 13, 2006 11:26 AM
> To: ccielab@groupstudy.com; rguyler@shp-dayton.org
> Subject: RE: Trunk Modes theory
>
>
> Greetings Rik,
> So what happens when you add the "nonegotiate" line to sw1?
> I'd be interested to hear - also what version are you running? Thanx, ~M
>
>
>
> >>> "Guyler, Rik" <rguyler@shp-dayton.org> 03/13/06 11:16 AM >>>
>
> Yes, a trunk gets formed. Here is the output from my switches (3550's)
> that I just labbed up for you. The config is not identical to yours but
> looks like it provides the same functionality:
>
> SW1#sh run int f0/24
> Building configuration...
>
> Current configuration : 93 bytes
> !
> interface FastEthernet0/24
> switchport trunk encapsulation isl
> switchport mode trunk
> end
>
> SW1#sh int trunk
>
> Port Mode Encapsulation Status Native vlan
> Fa0/24 on isl trunking 1
>
> Port Vlans allowed on trunk
> Fa0/24 1-4094
>
> Port Vlans allowed and active in management domain
> Fa0/24 1,888
>
> Port Vlans in spanning tree forwarding state and not pruned
> Fa0/24 1,888
> SW1#sh run int vlan 888
> Building configuration...
>
> Current configuration : 62 bytes
> !
> interface Vlan888
> ip address 10.111.111.111 255.0.0.0
> end
>
> SW1#
>
>
> SW2#sh run int f0/24
> Building configuration...
>
> Current configuration : 97 bytes
> !
> interface FastEthernet0/24
> switchport mode dynamic desirable
> end
>
> SW2#sh int trunk
>
> Port Mode Encapsulation Status Native vlan
> Fa0/24 desirable n-isl trunking 1
>
> Port Vlans allowed on trunk
> Fa0/24 1-4094
>
> Port Vlans allowed and active in management domain
> Fa0/24 1,888
>
> Port Vlans in spanning tree forwarding state and not pruned
> Fa0/24 1,888
> SW2#sh run int vlan 888
> Building configuration...
>
> Current configuration : 62 bytes
> !
> interface Vlan888
> ip address 10.222.222.222 255.0.0.0
> end
>
> SW2#ping 10.111.111.111
>
> Type escape sequence to abort.
> Sending 5, 100-byte ICMP Echos to 10.111.111.111, timeout is 2 seconds:
> !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/4
> ms SW2#sh cdp nei Capability Codes: R - Router, T - Trans Bridge, B -
> Source Route Bridge
> S - Switch, H - Host, I - IGMP, r - Repeater, P -
> Phone
>
> Device ID Local Intrfce Holdtme Capability Platform Port
> ID
> SW1 Fas 0/24 121 S I WS-C3550-2Fas
> 0/24
> R11 Fas 0/11 139 R S I Cisco 2801Fas
> 0/1
> R2 Fas 0/2 135 R 2500 Eth
> 0
> R3 Fas 0/3 144 R 2500 Eth
> 0
> R1 Fas 0/1 158 R 2500 Eth
> 0
> SW2#
>
>
> Rik
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> Geert Nijs
> Sent: Monday, March 13, 2006 10:21 AM
> To: ccielab@groupstudy.com
> Subject: Trunk Modes theory
>
> All,
>
> I am studying for my recertification and although i do understand the
> different trunking modes, there has been a large discussion between me
> and a colleague for the following specific situation:
>
> First Situation
> SW1 - Fa0/1
> switchport mode trunk
> switchport trunk mode isl
> switchport trunk nonegotiate
>
> SW2 - Fa0/1
> swichport mode desirable
>
>
> Is an ISL trunk being formed or NOT ?
> Trick: nonegotiate makes the port NOT send any DTP packets.
> I always thought that "desirable" NEEDED DTP packets from the other side
> to form a trunk (so: ON, AUTO or DESIRABLE) So i would say: NO, their is
> no trunk.
>
> Several books and docs seem to suggest that in this case, a trunk will
> be formed. I am unable to test right now. So what will happen ?
>
> regards,
>
> Geert Nijs
> Service Engineer
> CCIE #13729 <http://www.cisco.com/en/US/learning/le3/ccie/index.html>
>
>
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