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New Member

Catalyst 4006 Layer 3 Disconnect ?

Hello all,

I have a question about a 4006 Catalyst with the following modules installed:

Ws-x4013 1000BaseX supervisor version II

ws-x4232-l3 Route Proc.



The current configuration is a Collapsed Core design that has the Catalyst 4006 serving as a core and distribution layer. There are a total of 15 Bay Stack 4xx and 3xx series Layer 2 switches uplinked from the 4124fx ports (100/full). Each of the 15 fiber ports is associated to a unique VLAN. Each of the VLANS are configured to route IP and IPX (default settings). 4 of these fiber ports are also Bridging IEEE (For LAT traffic) with IRB for IP and IPX routing.

The switch and Route processor are configured through a single port channel (port channel 1). Each of the 15 VLANs were configured as sub-interfaces off port channel 1 (Port-channell1.%VLAN%) using dot1q encapsulation. There is one subinterface per VLAN. Each subinterface has an IP and IPX address as well as an IP helper address to forward DHCP broadcast requests. Rip is turned on.

Problem description:

For an estimated period of about 30 seconds - 2 minutes all layer 3 traffic (IP & IPX) was interrupted. During this interruption it appears that layer 2 traffic (bridging) was still working. I can validate that IP and IPX were interrupted by log files on our servers and complaints from the end user ip and ipx workstations. However I am unable to validate Bridged traffic. Since our LAT workstation and server users did not call us we are assuming that bridging was not affected. So far this has been the first and only event

It may also be helpful to know that this Catalyst 4006 switch was installed last Saturday (12-07-2002). Until this interruption it had been running in production without problem for 3+ days. Prior to production we had staged the environment for 2+ weeks.


Unfortunately we did not have system logging turned on during this event. Immediately after the communication drop I logged in the switch and RP to check CPU and Memory utilization. The switch CPU was between 10 - 15% utilization. The Route Processor CPU was between 1 - 3%

Currently I am logging the following information via SNMP to our Solarwinds station:

Router CPU utilization

Port channel utilization (including both Gig interfaces on backplane)

At this point I have no idea why this problem occurred. Any suggestions or thoughts would be greatly appreciated.



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New Member

Re: Catalyst 4006 Layer 3 Disconnect ?


i'll tell you what, is it possible for you to troubleshoot the problem VLAN by VLAN. Before connecting any of the other switches to the 4006, make sure that your 4006 is the root bridge (it make sense because this is a core/distribution switch). Give it a value say 10 or 20. Then start to connect one by one with the Bay switches. Each time that you connect a Bay switch into the 4006, make sure that the the 4006 is the root bridge for that particular VLAN. Also see if your network still function when going onto the Cisco one by one. It is also essential that you make sure that IPX routing also function when going onto the 4006. BTW, it probably help if you can publish the complain messages from the servers and the workstations.

Cisco Employee

Re: Catalyst 4006 Layer 3 Disconnect ?

what software versions are you using on the switch and the router-- from the description , it seems like you don; t have IRB enabled on the 4232-l3 router... which is correct since it is not supported on the 4232-l3 router module..

Also make sure the traffic within the vlan is not affected to eliminate the possibilty of the any layer 2 issues...

make sure the spanningtree is stable too