SDH Fiber Problem

jacob miller mmzinyi at
Mon Sep 19 07:58:39 UTC 2011

The entire link is an STM4 that has been channelised.
We are using 3xSTM1 for the EoS service.
The VCG group is configured with 3xSTM1.

Jacob Miller

----- Original Message -----
From: Alastair Johnson <aj at>
To: jacob miller <mmzinyi at>
Cc: "nanog at" <nanog at>
Sent: Monday, September 19, 2011 10:38 AM
Subject: Re: SDH Fiber Problem

On 9/19/2011 12:22 AM, jacob miller wrote:
> I have tried the pings and am able to ping through with a size of 1600 with the df-bit set
> without the df-bit am able to get up to 9000.
> The switched on bot ends hav been set to allow jumbo frames through and the system MTU size and routing MTU sizes are at 1998.
> The switch is a 2960 Cisco switch.
> I have set the mtu on the interface on the end router to 1600 and still unable to push meaningful traffic.

How much traffic are you trying to pass over the link?
How big is the underlying VCAT? Is it possible that this is 
misconfigured does not have enough bandwidth?
Depending on the underlying EoSONET/EoSDH bandwidth, you might need to 
pace traffic into the ADM to avoid overrunning buffers.


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