2950 Trunk or not to Trunk ?

[AJ69]

Is it possible to trunk two 2950 switches? I can trunk one of the 2950 to a 3650 with no problem. When I try and trunk a 2950 with another 2950....That's a no go....

[Prashanth Krishnappa]

You sure can. Post your configs. All you need on the links connecting the 2 2950s is "switchport mode dynamic desirable" or "switchport mode trunk"

[AJ69]

The config are listed below. The trunks are the same on both switches, but it just will not trunk between the two switches.

interface GigabitEthernet0/1

switchport mode trunk

!

interface GigabitEthernet0/2

switchport mode trunk

!

interface Vlan1

ip address 10.41.0.23 255.255.0.0

no shut

no ip route-cache

no ip domain-lookup

!

ip default-gateway 10.41.0.1

ip http server

!

[thisisshanky]

Can you paste a "sh int gi 0/1 switchport" output ?

[AJ69]

I can trunk to a 3650, but not to another 2950..

Output below..

GigabitEthernet0/2 is down, line protocol is down (notconnect)

Hardware is Gigabit Ethernet, address is 0014.6a35.e572 (bia 0014.6a35.e572)

MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,

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

Encapsulation ARPA, loopback not set

Keepalive set (10 sec)

Auto-duplex, Auto-speed, media type is RJ45

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

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

Last input never, output 17:07:50, output hang never

Last clearing of "show interface" counters never

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

Queueing strategy: fifo

Output queue: 0/40 (size/max)

[m.lammerse]

First thing that came to mind was that this could be a physical problem. For interconnecting 2 switches, you need a crosscable. Either that or you have faulty hardware. Did you try another port? The config looks ok to me.

HTH

Marcel

[singh.ashish]

Hi,

Wat is the ios version of both 2950 switches?

Did u try to configure some other port?

regards...

Ashish singh

[singh.ashish]

Hi,

yes it is possible to trunk Two 2950 switches. 2950 having some limitation like it only support 802.1q trunking and do not support ISL trunking.

regards...

Ashish Singh

[AJ69]

The IOS IS 12.1 Used the "switchport mode trunk" command Also, tried swapping cables from a 3560 and 2950 trunk. Trunk came back up, but 2950 to 2950 trunk is still dead. I'm lost.... I read something about "EtherChannel"...?

[m.lammerse]

What's your VTP configuration? Are the 2950's in the same domain with the same password? I believe you can use the 'show vtp domain' and 'show vtp status' to check.

HTH,

Marcel

[thisisshanky]

AJ,

First check if the following things are proper.

1. A cross cable is used to interconnect the two switches - ethernet cross over or a fiber cable with Rx and Tx pins crossed so that you do see a link light on either ports of the 2950.

2. Configure Vlan 1 interface on both switches and configure them with an IP (which is typically) a management vlan.

switch 1

--------

int vlan 1

no shut

ip add x.x.x.1 255.255.255.0

switch 2

--------

int vlan 1

no shut

ip add x.x.x.2 255.255.255.0

3. The port that connects between the two switches are configured with Mode trunk (which you have already done)

int fa0/24

switchport mode trunk

(Default trunking method is 802.1q, it doesnt support ISL)

4. Verify that Trunking is on using command...

show int fa0/24 switchport

5. Regarding VTP - If you run multiple vlans, its recommended to run VTP with one switch as VTP server and has the master database of vlans. All other switches are vtp client.

Switch 1

-------

Switch#vlan database

Switch(vlan)#vtp server (or vtp mode server)

Switch(vlan)#vtp domain cisco.com

Switch(vlan)#vlan 2 name SERVER

Switch(vlan)#vlan 3 name PHONE

Switch(vlan)#vlan 4 name COMPUTERS

Switch(vlan)#exit

Switch 2

--------

Switch(vlan)# vtp client (or vtp mode client)

Switch(vlan)#vtp domain cisco.com

Switch(vlan)#exit

The above configs should create vlan 2 and 3 on Switch 1 and configures it as a VTP server. Switch #2 will be VTP Client and if you do a Sh Vlan on Switch #2 you should see Vlan 2 and 3 in its database, if VTP is working correctly. This also means trunking is working properly across the two switches.

6. Configure two ports on each switch as part of vlan 2 (or 3) and ping between them.

Switch 1

-------

int fa0/1

switchport mode access

switchport access vlan 2

Switch 2

-------

int fa0/1

switchport mode access

switchport access vlan 2

HTH

[AJ69]

All this looks correct. Now here is the situation. All switches are being implemented are set for server. No VTP domain on any switch. It's kind of funny because I can trunk between two different model switches with none of the VTP configurations. There are no LED's lit on any of the switches ports where the crossover cable is connected. What gives?

[thisisshanky]

VTP is not mandatory for trunking to work. It just simplifies the process of administering vlans (centralized administration rather than creating the same vlans on each switch)

You say you dont have link lights on the ports where the crossover cable is connected. This could be bad cable. Does the same crossover cable work between the 2950 and other switch (3750 or 3550) ? Or if this is a custom made cable, have you verified the pin outs, whether they are crimped correct ?

[thisisshanky]

Did you finally solve this problem ?

[AJ69]

Yes, I think there is some type of issue trying to trunk two gigabit interfaces between the 2950 switches. I just made fa0/48 a trunk to the Gi0/1 of the other switch. Problem solved.... Thanks for your input...