Strange problem on NPE-G1 Gigabiteth tx_underflow

[simone.barbarella]

Hello all,

i have a 7206VXR NPE-G1 (IOS 12.4(18)) fitted with 2xPA-A3-OC3MM, 1xPA-A3-OC3SMI and 1xPA-A3-E3. I'm terminating DSL customers using Gi0/2 for uplink.

The Gigabit port is simply configured:

interface GigabitEthernet0/2
ip address xxx.xxx.xxx.xxx 255.255.255.252
duplex auto
speed auto
media-type rj45
negotiation auto

The other end is connected to a Cisco 2960G with identical port configuration.

Sometimes the interface starts to behave badly and output errors counter starts to increase without any apparent reason. If i do a show controller, i see that the errors are due to tx_underflow. What's is strange is that if i cycle down/up any of the ATM interfaces, the problem disappears and come back later (30 mins to 7 hours). I see no errors on the 2960G port. I'm unsure if this could be an IOS bug or a bad hardware, i tried changing port to Gi0/1 but had the same results. Any hint?

Simone

[Reza Sharifi]

Hi Simone,

Have you replaced the cable?

Reza

[Giuseppe Larosa]

Hello Simone,

so you have 3 STM-1 ATM links and one ATM E3 on this C7200?

I'm afraid it is too much for it.

I remember other threads where poor performances between POS or ATM port adapters and built in GE ports on C7200 NPE-G1 or NPE-G2 have been reported.

That is the performance between GE ports of NPE-G1 are better then the case where traffic goes between GE ports and WAN port adapters

your case is worse because the system is not behaving correctly.

Hope to help

Giuseppe

[simone.barbarella]

To Reza: i haven't tried it yet.. i think that would be my next step

To giuslar: that interface (Gi0/2) carries about 200Mbps IN and 80Mbps OUT in peak traffic times. I have the same setup on a NPE-G2 and never had any problem. I tought about possibly poor performance problems, but since the setup is inside "bandwidth points" limit i hoped that the 7206 could support the traffic. Do you advice me to split the setup adding another 7206?

Simone

[Giuseppe Larosa]

Hello Simone,

before adding a new C7206 I would try to connect both gigabit ports to two different backbone vlans to have two equal cost paths towards core.

Changing the cable as suggested by Reza is always a wise step.

Hope to help

Giuseppe