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New Member

Trunk Port for 2950 and 2960G

Hi Guys,

I have tried connecting 2 switch using a trunk port in able for VLAN to run on 2950 switch, 2950 and 2960G, but the problem is, it keeps going up and down when I check the logs. The client experienced intermittent network connection by this problem. What seems to be the problem here? I already replaced the cables.

Here is the config:

They are connected via cross-cable

2950:

Int f0/24 --> 100mbps port

switchport mode trunk

2960G:

Int G0/1 --> 1Gbps port

switchport mode trunk

*I believe they will auto negotiate their current speed and duplex.

Thanks in advance.

Cheers!

15 REPLIES
New Member

Re: Trunk Port for 2950 and 2960G

Do a "show ip int description" in each switch and verify both connected ports have the same speed and duplex settings.

New Member

Re: Trunk Port for 2950 and 2960G

Sorry.... do a "show interfaces status".

New Member

Re: Trunk Port for 2950 and 2960G

Yes, they have the same settings.

Here it is:

int g0/2

MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,

reliability 255/255, txload 1/255, rxload 1/255

Encapsulation ARPA, loopback not set

Keepalive set (10 sec)

Full-duplex, 100Mb/s, media type is 10/100/1000BaseTX

input flow-control is off, output flow-control is unsupported

ARP type: ARPA, ARP Timeout 04:00:00

Last input 00:00:23, output 00:00:00, output hang never

Last clearing of "show interface" counters 5d18h

Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0

Queueing strategy: fifo

Output queue: 0/40 (size/max)

5 minute input rate 21000 bits/sec, 21 packets/sec

5 minute output rate 495000 bits/sec, 180 packets/sec

5180581 packets input, 1243581478 bytes, 0 no buffer

Received 62493 broadcasts (0 multicast)

0 runts, 0 giants, 0 throttles

2 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored

0 watchdog, 30119 multicast, 0 pause input

0 input packets with dribble condition detected

179416978 packets output, 2694243274 bytes, 0 underruns

0 output errors, 0 collisions, 0 interface resets

0 babbles, 0 late collision, 0 deferred

0 lost carrier, 0 no carrier, 0 PAUSE output

0 output buffer failures, 0 output buffers swapped out

int f0/24

MTU 1500 bytes, BW 100000 Kbit, DLY 1000 usec,

reliability 255/255, txload 1/255, rxload 1/255

Encapsulation ARPA, loopback not set

Keepalive set (10 sec)

Full-duplex, 100Mb/s, media type is 100BaseTX

input flow-control is unsupported output flow-control is unsupported

ARP type: ARPA, ARP Timeout 04:00:00

Last input 00:00:00, output 00:00:00, output hang never

Last clearing of "show interface" counters 5d18h

Input queue: 2/75/0/0 (size/max/drops/flushes); Total output drops: 0

Queueing strategy: fifo

Output queue: 0/40 (size/max)

5 minute input rate 504000 bits/sec, 180 packets/sec

5 minute output rate 22000 bits/sec, 22 packets/sec

179389710 packets input, 2690183405 bytes, 0 no buffer

Received 26481884 broadcasts (0 multicast)

0 runts, 0 giants, 0 throttles

4510 input errors, 3566 CRC, 243 frame, 0 overrun, 0 ignored

0 watchdog, 17984825 multicast, 0 pause input

0 input packets with dribble condition detected

5180070 packets output, 1243477217 bytes, 0 underruns

0 output errors, 0 collisions, 0 interface resets

0 babbles, 0 late collision, 0 deferred

0 lost carrier, 0 no carrier, 0 PAUSE output

0 output buffer failures, 0 output buffers swapped out

Purple

Re: Trunk Port for 2950 and 2960G

Int f0/24 has a fair amount of errors on it seeing it was cleared only 5 days ago. This looks like it is the input side going into the f0/24 . This is usually a physical layer issue. Also try a different port , one at a time on each end. The 2950 only supports dot1q , not sure about the 2960 but that is a direct replacement for the 2950 model.

Re: Trunk Port for 2950 and 2960G

try to hard code your interface config to:

2950:

Int f0/24

speed 100

duplex full

2960G:

Int G0/1

speed 100

duplex full

kindly post the logs and config of each switch interface.

New Member

Re: Trunk Port for 2950 and 2960G

I have tried to hardcode the interfaces, but still it is going up and down.

Here is the logs, almost the same with 2950 up and down status:

%LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/2, changed state to up

%LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/2, changed state to down

%LINK-3-UPDOWN: Interface GigabitEthernet0/2, changed state to down

%LINK-3-UPDOWN: Interface GigabitEthernet0/2, changed state to up

%LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/2, changed state to up

%LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/2, changed state to down

%LINK-3-UPDOWN: Interface GigabitEthernet0/2, changed state to down

Re: Trunk Port for 2950 and 2960G

are both trunk set to same encapsulation? try using dot1q on both ends. make sure the gig port is set to 100 speed to adjust for the other fast e port. do a show run int x and post it here.

New Member

Re: Trunk Port for 2950 and 2960G

They are both set to trunk but I have'nt set any encapsulation? I'll try that tomorrow and let you know. Btw, is the 2950 and 2960G are compatible? Thanks.

New Member

Re: Trunk Port for 2950 and 2960G

My understanding was that the only trunk encapsulation type available on the 2950 and 2960 was dot1q.

What command would one use to enable isl or dot1q on a 2950 or 2960? It's not "switchport trunk encapsulation dot1q" like with other switches.

Hall of Fame Super Gold

Re: Trunk Port for 2950 and 2960G

2950 & 2960 have only one trunk encapsulation and it's Dot1Q.

Have you tried changing the cables? Since the 2960 is MDI/MDIX enable (make sure it is), cross-over or straight through won't make a difference.

In the 2950, did you create the VLAN on the VLAN Database?

Try other switches, I'm suspecting the 2950 is faulty.

New Member

Re: Trunk Port for 2950 and 2960G

Hi,

please change to a straight cable and tells us whats the outcome. thanks

Re: Trunk Port for 2950 and 2960G

Hi Irvine,

2940/2950 only supports 802.1Q and since its only support 802.1Q its the default.

2960 supports ISL and 802.1Q and the default is ISL. Set the encapsulation to 802.1Q

Regards,

Dandy

Hall of Fame Super Gold

Re: Trunk Port for 2950 and 2960G

Hi Dandy,

I'm using IOS 12.2(44)SE & 12.2(46)SE for my 2960 and I'm fairly certain this particular model will only support 802.1Q encapsulation.

Can you verify this? If you are able to get ISL, can you let me know how you've been able to achieve this? :)

Thanks.

Re: Trunk Port for 2950 and 2960G

Hi Leo,

You're right it doesn support ISL :)

I thought I was using ISL between my 2960 and 3750. Its 802.1Q

Regards,

Dandy

Hall of Fame Super Gold

Re: Trunk Port for 2950 and 2960G

Hi Dandy,

WHEW! I thought this was a new feature being introduced. Thanks for setting my mind at ease!

:)

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