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Community Member

A strange DTP infomation

Hello,

I have 2 switchs: Cat2950 and Cat3550 connected via Fa0/10

On my cat2950, i configure port fa0/10 to mode dynamic auto and the other end

with dynamic desirable. The trunking works fine but when i look at dtp

information, i see something strange:

DTP information for FastEthernet0/10:

TOS/TAS/TNS: TRUNK/DESIRABLE/TRUNK <---trunking is on

TOT/TAT/TNT: 802.1Q/802.1Q/802.1Q <---encap dot1q

But int the statistics:

2204 native, 2204 software encap isl, 0 isl hardware native <-----what does this mean: 2204 packets encap isl ? ---->

we all know that cat2950 does not support isl, so what does this infomation mean ?

Thanks

-------------------------------------------------

Switch3550#sh run int fa0/10

!

interface FastEthernet0/10

switchport mode dynamic desirable

end

Switch3550#sh dtp int fa0/10

DTP information for FastEthernet0/10:

TOS/TAS/TNS: TRUNK/DESIRABLE/TRUNK <---trunking is on

TOT/TAT/TNT: 802.1Q/802.1Q/802.1Q <---encap dot1q

Neighbor address 1: 000C85A5700A

Neighbor address 2: 000000000000

Hello timer expiration (sec/state): 9/RUNNING

Access timer expiration (sec/state): 279/RUNNING

Negotiation timer expiration (sec/state): never/STOPPED

Multidrop timer expiration (sec/state): never/STOPPED

FSM state: S6:TRUNK

# times multi & trunk 0

Enabled: yes

In STP: no

Statistics

----------

2200 packets received (3 good)

2197 packets dropped

0 nonegotiate, 0 bad version, 2197 domain mismatches,

0 bad TLVs, 0 bad TAS, 0 bad TAT, 0 bad TOT, 0 other

4408 packets output (4408 good)

2204 native, 2204 software encap isl, 0 isl hardware native <-----what does this from: 2204 packets encap isl ? ---->

0 output errors

-----------------------------------------------------

and this is on Cat2950:

Switch2950#sh run int fa0/10

Building configuration...

Current configuration : 69 bytes

!

interface FastEthernet0/10

switchport mode dynamic auto

end

Switch2950#sh dtp int fa0/10

DTP information for FastEthernet0/10:

TOS/TAS/TNS: TRUNK/AUTO/TRUNK

TOT/TAT/TNT: 802.1Q/802.1Q/802.1Q

Neighbor address 1: 000DBCA8838A

Neighbor address 2: 000000000000

Hello timer expiration (sec/state): 25/RUNNING

Access timer expiration (sec/state): 294/RUNNING

Negotiation timer expiration (sec/state): never/STOPPED

Multidrop timer expiration (sec/state): never/STOPPED

FSM state: S6:TRUNK

# times multi & trunk 0

Enabled: yes

In STP: no

Statistics

----------

2212 packets received (12 good)

2200 packets dropped

0 nonegotiate, 0 bad version, 2200 domain mismatches,

0 bad TLVs, 0 bad TAS, 0 bad TAT, 0 bad TOT, 0 other

4408 packets output (4408 good)

2208 native, 2200 software encap isl, 0 isl hardware native

0 output errors

0 trunk timeouts

4 link ups, last link up on Mon Mar 01 1993, 04:26:15

3 link downs, last link down on Mon Mar 01 1993, 04:25:43

2 REPLIES
Silver

Re: A strange DTP infomation

Yes,u r right.right from 2950 series switches, they don't support ISL, support only 802.1q.But,check out the version of the ios in your switches.

Do u get any of the error messages like the one below from 3550.if so, a remedy is also provided here.

Error Message DTP-5-ILGLCFG: Illegal config (on, isl--on, dot1q) on [chars].

Explanation This message means that one end of the trunk is configured as on, ISL, and the other end is configured as on, 802.1Q. [chars] is the interface.

Recommended Action This configuration is illegal and will not establish a trunk between two switches. You must change the encapsulation type so that both ends of the trunk match

Community Member

Re: A strange DTP infomation

Unfortunately, i didn't get any error message as you listed above.

The 2950 running 12.1(22)EA1 and 3550 running 12.2(25)SEA.

I was thinking that it's an ios bug maybe ???

Thanks

------------------------------------------------

SW3550-2#sh ver

Cisco IOS Software, C3550 Software (C3550-I5Q3L2-M), Version 12.2(25)SEA, RELEAS

E SOFTWARE (fc)

Copyright (c) 1986-2005 by Cisco Systems, Inc.

Compiled Tue 25-Jan-05 18:57 by antonino

ROM: Bootstrap program is C3550 boot loader

SW3550-2 uptime is 8 hours, 22 minutes

System returned to ROM by power-on

System image file is "flash:/c3550-i5q3l2-mz.122-25.SEA.bin"

Cisco WS-C3550-24 (PowerPC) processor (revision J0) with 65526K/8192K bytes of m

emory.

Processor board ID CAT0746Y0KD

Last reset from warm-reset

Running Layer2/3 Switching Image

----------------------------------------------------

Switch_6#sh ver

Cisco Internetwork Operating System Software

IOS (tm) C2950 Software (C2950-I6Q4L2-M), Version 12.1(22)EA1, RELEASE SOFTWARE

(fc1)

Copyright (c) 1986-2004 by cisco Systems, Inc.

Compiled Mon 12-Jul-04 08:18 by madison

Image text-base: 0x80010000, data-base: 0x8055C000

ROM: Bootstrap program is C2950 boot loader

Switch_6 uptime is 2 hours, 16 minutes

System returned to ROM by power-on

System image file is "flash:/c2950-i6q4l2-mz.121-22.EA1.bin"

cisco WS-C2950-24 (RC32300) processor (revision G0) with 20873K bytes of memory.

Processor board ID FOC0806Z177

Last reset from system-reset

Running Standard Image

24 FastEthernet/IEEE 802.3 interface(s)

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