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New Member

CRC and error in fast ethernet

Dear all,

I'm facing lot of errors and CRC on LAN interface. any one can help to determine the problem where,

I'm connecting Fastethernet to Mentat accelator and then to PIX firewall. all interfaces touch the router configured full duplex and 100Mbps. any advice will be much appreciated.

interface FastEthernet0/0

ip address *.*.*.* secondary

ip address *.*.*.*

no ip redirects

no ip proxy-arp

ip accounting precedence input

ip route-cache flow

ip policy route-map oracle-vip

load-interval 30

speed 100


no cdp enable


FastEthernet0/0 is up, line protocol is up

Hardware is AmdFE, address is 0008.a3b6.6860 (bia 0008.a3b6.6860)

Internet address is *.*.*.* /27

MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,

reliability 255/255, txload 1/255, rxload 1/255

Encapsulation ARPA, loopback not set

Keepalive set (10 sec)

Full-duplex, 100Mb/s, 100BaseTX/FX

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 00:01:01

Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0

Queueing strategy: fifo

Output queue: 0/40 (size/max)

30 second input rate 205000 bits/sec, 82 packets/sec

30 second output rate 587000 bits/sec, 86 packets/sec

5206 packets input, 1596894 bytes

Received 0 broadcasts, 0 runts, 0 giants, 0 throttles

946 input errors, 946 CRC, 93 frame, 0 overrun, 0 ignored

0 watchdog

0 input packets with dribble condition detected

5374 packets output, 4562932 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 output buffer failures, 0 output buffers swapped out

New Member

Re: CRC and error in fast ethernet

check cables lengths and integrity. also 100BaseTX/FX reported by sh int seems strange for me. is it a "twin port" where only one physical connector is active in any time? try to hardcode media for this int in that case.

New Member

Re: CRC and error in fast ethernet

here is hardware for F0/0

cable is showing amber this means there is a lost in cable or mismatching i confused now :)? but still 123 input errors, 123 CRC, 60 frame increased? Maybe missmatch with Mentat accelator?

sh controllers f0/0

Interface FastEthernet0/0

Hardware is AMD Am79c971

ADDR: 63D16774, FASTSEND: 60032A04, MCI_INDEX: 0


Route Cache Flag: 203

LADRF=0x0000 0x0100 0x0000 0x0000

CSR0 =0x00000072, CSR3 =0x00001044, CSR4 =0x0000491D, CSR15 =0x00000180

CSR80 =0x00009900, CSR114=0x00000000, CRDA =0x0799AEE0, CXDA =0x0799B420

BCR9 =0x00000001 (full-duplex)

CSR5 =0x00000001, CSR7 =0x00000820, CSR100=0x0000F000, CSR125=0x00005C3C

BCR2 =0x00000000, BCR9 =0x00000001, BCR18 =0x000019E0, BCR22 =0x0000FF06

BCR25 =0x000000FF, BCR26 =0x00000080, BCR27 =0x00000010, BCR32 =0x00004480

HW filtering information:

Promiscuous Mode Disabled, PHY Addr Enabled, Broadcast Addr Enabled

PHY Addr=0008.A3B6.6860, Multicast Filter=0x0000 0x0100 0x0000 0x0000

amdp2_instance=0x63D17F24, registers=0x38000000, ib=0x799AB20

rx ring entries=64, tx ring entries=128

rxring=0x799AB80, rxr shadow=0x63D18190, rx_head=54, rx_tail=0

txring=0x799AFC0, txr shadow=0x63D182BC, tx_head=70, tx_tail=70, tx_count=0

Software MAC address filter(hash:length/addr/mask/hits):

0xC0: 0 0100.0ccc.cccc 0000.0000.0000 0

spurious_idon=0, filtered_pak=0, throttled=0, enabled=0, disabled=0

rx_framing_err=0, rx_overflow_err=0, rx_buffer_err=0

rx_bpe_err=0, rx_soft_overflow_err=0, rx_no_enp=0, rx_discard=0

tx_one_col_err=3, tx_more_col_err=16, tx_no_enp=0, tx_deferred_err=68

tx_underrun_err=0, tx_late_collision_err=0, tx_loss_carrier_err=0

tx_exc_collision_err=0, tx_buff_err=0, fatal_tx_err=0

hsrp_conf=0, need_af_check=0


PHY registers:

Register 0x00: 2100 780D 7810 0003 0101 0000 0000 0000

Register 0x08: 0000 0000 0000 0000 0000 0000 0000 0000

Register 0x10: 0000 0000 4000 0000 3CFB 0010 0000 0002

Register 0x18: 0001 0000 0000 0000 0000

New Member

Re: CRC and error in fast ethernet

Some thoughts:

You state that all devices are configured for full duplex, but it looks to me like symptoms of a duplex mismatch still.

Double check the device that is on the other end of fa0/0 is set to full duplex.

Try setting fa0/0 to half duplex and watch the counters some more.

Is the other device maybe physically still at half even though the config says full?

Do they both operate fine when configured for half? (And give regular collision related errors?)

New Member

Re: CRC and error in fast ethernet

Thanks all,

I have tried to make it half duplex. after monitoring there is no errors appearing.?

But I'm affraid if that will affect the performance?

Is it OK to leave it half?

New Member

Re: CRC and error in fast ethernet

Half duplex is perfectly fine on a link where you are not expecting a lot of raw-throughput. The only time you will notice a performance difference is if you intend to do 80% or more bandwitdh (in 100mbps that is 8 Megabytes per second) each way simultaneously. you can do one way at 8, or two ways at 4. (Very roughly speaking).

For obvious reasons, full-duplex will give you up to 2x the bandwidth available because the bidirectional traffic is not sharing the bandwidth.

New Member

Re: CRC and error in fast ethernet

But when I configured the link with Half dublex I got lot of collisions and deferred and both are increased with average of hour monitoring? is it normal situation and have to believe it?

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