[c-nsp] CPU comparison - bridge vs. route on 7206?

[Chris Hale]

We have a set of 7206VXR's, NPE400 CPUs on each end of a point to point OC3
using PA-POS-OC3 cards.  We bridge these circuits through a PA-GE interface
(essentially turning the 7206's into a OC-3 to GigE converter) with a single
bridge group.

We are trying to push nearly 130-140Mbps, but per the MRTG graphs, we seem
to be capping @ ~110Mbps.  The CPU is also averaging 80-90%.  We're seeing a
large number of input errors (ignored, total of 5% of input packets) and a
fair amount of output pauses (0.12% of output packets).

GigabitEthernet1/0 is up, line protocol is up
  Hardware is WISEMAN, address is 0016.46e6.1c1c (bia 0016.46e6.1c1c)
  MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,
     reliability 255/255, txload 36/255, rxload 16/255
  Encapsulation ARPA, loopback not set
  Keepalive set (10 sec)
  Full-duplex, 1000Mb/s, link type is autonegotiation, media type is unknown
media type
  output flow-control is XON, input flow-control is XON
  ARP type: ARPA, ARP Timeout 04:00:00
  Last input 00:00:00, output 00:00:00, output hang never
  Last clearing of "show interface" counters 12w0d
  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 208
  Queueing strategy: fifo
  Output queue: 0/40 (size/max)
  30 second input rate 66046000 bits/sec, 29231 packets/sec
  30 second output rate 141617000 bits/sec, 31690 packets/sec
     2816822087 packets input, 1367339773 bytes, 0 no buffer
     Received 7138653 broadcasts, 0 runts, 0 giants, 0 throttles
     143326584 input errors, 0 CRC, 0 frame, 481945 overrun, 142844639
ignored
     0 watchdog, 4536607 multicast, 0 pause input
     0 input packets with dribble condition detected
     3993978307 packets output, 979813878 bytes, 0 underruns
     0 output errors, 0 collisions, 0 interface resets
     0 babbles, 0 late collision, 0 deferred
     4 lost carrier, 0 no carrier, 4808187 pause output
     0 output buffer failures, 0 output buffers swapped out

If we move this to a routed infrastructure with CEF, can we expect the CPU
to drop considerably?   The routing will be static only, very simple config
with no ACLs, no policy maps, etc.  We're just trying to get the routers to
let us push as much of the OC3 bandwidth as possible.

We would rather not upgrade the NPE400's if possible.  The internal LAN
equipment is Nortel L3 switches which don't seem to support flow-control.

Thanks in advance for any ideas.

Chris

-- 
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Chris Hale
chale99 at gmail.com