Во! У меня похожая проблема!
Есть 7206 и Catalyst 3750. В среднем раз в пол-минуты теряются пинги на 72-ю циску. Она включена в каталист. Пинги на каталист не пропадают. Причем по разным виланам похожая картина. 1-й вилан не использую. Между цисками гигабит по оптике (сегодня поставил), до того была медь 100Мб - та же история. Т.е. пинги пропадают, параметры про дропы растут, как на дрожжах:
Input queue: 3/75/95218/449819 (size/max/drops/flushes); Total output drops: 1145144
Что еще можно сделать - не знаю.
да, на каталистовском интерфейсе ошибок вообще нет.
На всякий случай вот sh run и sh int интерфейсов:
(gi0/1 - на 72-й циске, gi2/0/4 - на 3750)

sh int gi0/1
GigabitEthernet0/1 is up, line protocol is up
  Hardware is BCM1250 Internal MAC, address is 0019.aacd.581b (bia 0019.aacd.581b)
  Description: To inside
  MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,
     reliability 255/255, txload 1/255, rxload 2/255
  Encapsulation ARPA, loopback not set
  Keepalive set (10 sec)
  Full Duplex, 1000Mbps, 1000BaseLX, Auto-negotiation, media type is LX
  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 never
  Input queue: 3/75/97782/457211 (size/max/drops/flushes); Total output drops: 1153471
  Queueing strategy: fifo
  Output queue: 0/40 (size/max)
  5 minute input rate 7862000 bits/sec, 3168 packets/sec
  5 minute output rate 6754000 bits/sec, 1615 packets/sec
     185464608 packets input, 783339605 bytes, 0 no buffer
     Received 35297067 broadcasts (0 IP multicasts)
     0 runts, 0 giants, 2823 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     0 watchdog, 61620 multicast, 0 pause input
     145346041 packets output, 3055984970 bytes, 0 underruns
     8 output errors, 0 collisions, 6 interface resets
     0 babbles, 0 late collision, 0 deferred
     8 lost carrier, 0 no carrier, 0 PAUSE output
     0 output buffer failures, 0 output buffers swapped out

sh run int gi0/1
Building configuration...

Current configuration : 273 bytes
!
interface GigabitEthernet0/1
description To inside
no ip address
ip flow ingress
no ip route-cache cef
no ip mroute-cache
media-type gbic
speed auto
duplex auto
negotiation auto
end

sh int gi2/0/4
GigabitEthernet2/0/4 is up, line protocol is up (connected)
  Hardware is Gigabit Ethernet, address is 0014.69ef.9984 (bia 0014.69ef.9984)
  Description: To 10.25.0.19 opt
  MTU 1546 bytes, BW 1000000 Kbit, DLY 10 usec,
     reliability 255/255, txload 2/255, rxload 1/255
  Encapsulation ARPA, loopback not set
  Keepalive not set
  Full-duplex, 1000Mb/s, link type is auto, media type is 1000BaseLX SFP
  input flow-control is on, output flow-control is unsupported
  ARP type: ARPA, ARP Timeout 04:00:00
  Last input 00:00:02, output 00:00:24, output hang never
  Last clearing of "show interface" counters never
  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
  Queueing strategy: fifo
  Output queue: 0/40 (size/max)
  5 minute input rate 6684000 bits/sec, 1646 packets/sec
  5 minute output rate 7930000 bits/sec, 3326 packets/sec
     2145627 packets input, 1044829874 bytes, 0 no buffer
     Received 955 broadcasts (0 multicast)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     0 watchdog, 27 multicast, 0 pause input
     0 input packets with dribble condition detected
     4325153 packets output, 1245674211 bytes, 0 underruns
     0 output errors, 0 collisions, 4 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

sh run int gi2/0/4
Building configuration...

Current configuration : 360 bytes
!
interface GigabitEthernet2/0/4
switchport trunk encapsulation dot1q
switchport trunk allowed vlan ....................
switchport mode trunk
flowcontrol receive on
spanning-tree bpdufilter enable
spanning-tree bpduguard enable
end