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New Member

trunks between 2950s stop working and wont come back

I've seen this happen on 2 different 'pairs' of 2950s, so it's time to investigate. The scenareo:

simple trunk (no vlan definitions) between 2 2950s. 1 switch looses power, when power is restored, the switch that didn't lose power doesn't pass any traffic. The interface is up (link and administrativly up) the logs don't show anything other than the interface went down and came back up. here's a sample port:

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

interface FastEthernet0/23

description new Feed from phone room switch

switchport mode trunk

no ip address

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

I'm not using spanning-tree, there aren't any redunant paths. Its worked fine for months (until a ups failure), I set up a new port on the switch and swing the cable and it comes up. Any ideas?

thanks!

7 REPLIES
Silver

Re: trunks between 2950s stop working and wont come back

not sure of the issue, check out the following link for configuring trunks across 2950 series switches :

http://www.cisco.com/en/US/products/hw/switches/ps607/products_configuration_example09186a008014c203.shtml

hope this helps.

Purple

Re: trunks between 2950s stop working and wont come back

I guess the other question would be why are you trunking if you are only using vlan 1 without spanning tree ???

New Member

Re: trunks between 2950s stop working and wont come back

Hello,

I know this is an old post... but I am posting here in case this is viewed by anyone with a possible solution.

Our organization has multiple locations configured the same way:

(x2) cross connected 2950 switches in trunk mode, configured the follwing way per each interface (fa0/19):

!
interface FastEthernet0/19
no ip address
duplex full
speed 100
no cdp enable
spanning-tree portfast
!

Our problem is similar to the one explained in this initial post. The switches are auto-trunked via port #19.

Let's call one switch "A" and one switch "B"

Whenever power is removed from one of the switches (Switch A), and it has completed a restart, the opposite switch (Switch B ..the one which was not powered off) will not return to a "Trunked" state. When you run the "show int status" command, it shows that the port is "connected". Even though the switch which was initially restarted returns to "Trunked" mode.

We have seen this with a few of our 2950's across the infrastructure.

The bottom line is that restarting one of the switches causes the other to lose the trunked state. The only was to correct the issue is to restart the opposite switch as well.

The IOS version is 12.1 (9) EA1d .. I know it's old, however we cannot upgrade it at this time due to policies within the organization.

Could anybody shed some light on this?

Thanks in advance..

Hall of Fame Super Gold

Re: trunks between 2950s stop working and wont come back

I've seen this happen with auto-Trunk negotiation in early IOS.  The easiest way was to configure "switchport mode trunk" with "switchport nonegotiate" as optional.  (I configure both).

New Member

Re: trunks between 2950s stop working and wont come back

Wow! I can't believe someone replied so quick...  thought this thread was a goner..

Anyway, Thanks for the quick response leolaohoo!

I will give this a shot and see if it corrects the issue.

Do you know if this was addressed anywhere in the Official Cisco documentation (ie. Technotes, Release notes etc.)?

It would be a great to have something like that to help justify upgrading the IOS across the board.

It is odd, we have seen some 2950's do this, and then others not (even with the same IOS version!)

I'm thinking maybe a bad production run on some of them, or a manufacturer defect somewhere along the line.

Thanks again for the reply... Big Time!

We have been banging our heads against the wall with this for awhile.

Hall of Fame Super Gold

Re: trunks between 2950s stop working and wont come back

Hi Ray,


I've been trying to hold my tongue regarding how ancient of a version of the IOS you are running.  The latest and last IOS of the 2950 series switches is EA13.  I recommend that you upgrade.


If you believe our post if of any help to you, may I request you rate them appropriately? Thank you very much.

New Member

Re: trunks between 2950s stop working and wont come back

Hi Leo,

Yes, I am aware of how "Ancient" the IOS version is...

However, unfortunately I am not the one who ultimately makes the decision on upgrading the IOS, even though it would probably correct some issues as well as add some additional functionality.

In order to do any kind of change or perform an upgrade on the IOS version, it would have to be done organization-wide on over 100 switches.

Documentation would need to be updated as well.

I think we need to do this anyway (as do other people in the tech area here), that is why I am trying to put together some official documentation of the issue to present to management.

I will be trying your suggestion, and I will let you know how it works out.

Thanks again for your help.. it's much appreciated.

-Ray

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