Trying to make CRC errors with scapy

I'm trying to make CRC errors with scapy on Linux, but the Cisco 3750 and 2950 switches won't show any CRC or FCS errors. I just wanted to make some to help someone testing SNMP. Wiresharks running on both my Linux eth2 port and on the SPAN port show "Frame check sequence: 0x61616161 [incorrect, should be 0xcfc42298]".

Any ideas on what could be the issue? I'm guessing Cisco just expects the FCS to be somewhere else.

[root@localhost ~]# scapy
INFO: Can't import python gnuplot wrapper . Won't be able to plot.
INFO: Can't import PyX. Won't be able to use psdump() or pdfdump().
WARNING: No route found for IPv6 destination :: (no default route?)
Welcome to Scapy (2.0.0.10 beta)
>>> from scapy.all import *
>>> import socket
>>> s = socket.socket(socket.AF_PACKET, socket.SOCK_RAW)
>>> s.bind(("eth2",0))
>>> frame = Ether()/IP(dst="10.10.11.254")/ICMP()/"XXXXXXXXXXXXXXX"
>>> s.send(str(frame)+"aaaa")
61
>>>


LABSWITCH#sh int gi0/1
GigabitEthernet0/1 is up, line protocol is up (connected)
Hardware is Gigabit Ethernet, address is 0016.9d66.1bd9 (bia 0016.9d66.1bd9)
MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Full-duplex, 1000Mb/s, media type is RJ45
input flow-control is off, output flow-control is on
ARP type: ARPA, ARP Timeout 04:00:00
Last input never, output 00:00:09, output hang never
Last clearing of "show interface" counters 01:13:15
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 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
1359 packets input, 87114 bytes, 0 no buffer
Received 1347 broadcasts (0 multicast)
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
1408 packets output, 120119 bytes, 0 underruns
0 output errors, 0 collisions, 0 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


LABSWITCH#sh controllers ethernet-controller gigabitEthernet 0/1

Transmit Receive
137118 Bytes 120984 Bytes
1623 Frames 1813 Frames
1009 Multicast frames 0 FCS errors
58 Broadcast frames 0 Multicast frames
0 Pause frames 1786 Broadcast frames
0 Single defer frames 0 Control frames
0 Multiple defer frames 0 Pause frames
0 1 collision frames 0 Unknown opcode frames
0 2-15 collisions 0 Alignment errors
0 Late collisions 0 Length out of range
0 Excessive collisions 0 Symbol error frames
0 Total collisions 0 False carrier errors
0 Control frames 0 Valid frames, too small
0 VLAN discard frames 0 Valid frames, too large
0 Too old frames 0 Invalid frames, too small
0 Tagged frames 0 Invalid frames, too large
0 Aborted Tx frames 0 Discarded frames

Transmit and Receive
2362 Minimum size frames
1055 65 to 127 byte frames
12 128 to 255 byte frames
4 256 to 511 byte frames
0 512 to 1023 byte frames
3 1024 to 1518 byte frames
0 1519 to 1522 byte frames