[c-nsp] Dropping traffic on a Cat6k plattform

[gal.9430 at googlemail.com]

Hi there,

I've some problems on a Cat6k plattform with SUP720-3BXL running
15.1(1)SY1. On one port on a WS-X6724-SFP linecard the traffic differs
between interface stats and real life experiences.

!
interface GigabitEthernet4/1
 switchport
 switchport access vlan 53
 switchport mode access
 no cdp enable
!
interface Vlan53
 ip address x.x.x.x 255.255.255.248
 ipv6 address x:x:x::x/64
 ipv6 nd ra suppress
!

#show inter utilization Gi4/1
5 minute input/output port rates


Port       Rcv-Packet-Rate      Rcv-Bits-Rate
-----    -------------------- --------------------

 4/1            10732                37674000

Port       Xmit-Packet-Rate     Xmit-Bits-Rate
-----    -------------------- --------------------

 4/1            9521                 58149000

#show interface Gi4/1
GigabitEthernet4/1 is up, line protocol is up (connected)
  Hardware is C6k 1000Mb 802.3, address is 0019.0628.4d34 (bia
0019.0628.4d34)
  MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,
     reliability 255/255, txload 14/255, rxload 9/255
  Encapsulation ARPA, loopback not set
  Keepalive set (10 sec)
  Full-duplex, 1000Mb/s, media type is 1000BaseT
  input flow-control is off, output flow-control is off
  Clock mode is auto
  ARP type: ARPA, ARP Timeout 04:00:00
  Last input never, output never, output hang never
  Last clearing of "show interface" counters never
  Input queue: 0/2000/0/0 (size/max/drops/flushes); Total output drops: 0
  Queueing strategy: fifo
  Output queue: 0/40 (size/max)
  5 minute input rate 37755000 bits/sec, 10758 packets/sec
  5 minute output rate 58486000 bits/sec, 9557 packets/sec
     627435059 packets input, 252877736829 bytes, 0 no buffer
     Received 3457 broadcasts (3453 multicasts)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     0 watchdog, 0 multicast, 0 pause input
     0 input packets with dribble condition detected
     547916832 packets output, 402605377354 bytes, 0 underruns
     0 output errors, 0 collisions, 3 interface resets
     0 babbles, 0 late collision, 0 deferred
     0 lost carrier, 0 no carrier, 0 PAUSE output
     0 output buffer failures, 0 output buffers swapped out

Thought, that the reason is the uRPF check but this is disabled:

#show mls cef ip rpf

RPF global mode:        loose
RPF mpath mode:         pass

 Index   Interfaces
-------+----------------------------------------
   0
   1
   2
   3

On this port it _must_ be possible that traffic with other source can
pass. Former, on a *real* router plattform (NPE-G2), the same config
works as expected :-( Any ideas whats the reason for this problem?


Thanks,

Robert