[ixp1200] Transmitting pkts out of Giga ports

[chompi at softhome.net]

Hi all, 

I've recently tried sample code from chap9 Johnson and Kunze book and in 
DWB, the code works fine with Fast Eth ports. However, if I try to use GE 
ports, it only works when MTU<=192 (<=3 Mpkts per pkt). If there are >3 
Mpkts/pkt, the simulation halts with error "Transmit buffer underflow". Does 
this mean that the code is not filling up TFIFO fast enough?
Anyways, even if I set MTU<=192, I still cannot send out any traffic on real 
hardware (we are using ENP-2506). L3Fwdr reference design works fine on the 
board so I do not expect any hardware or configuration problems.
Did anybody encounter this issue before? Is there any sample code (in micro 
C) lying around that transmits data over GE ports? 

Any help is appreciated. 

Chompi.