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837 performance very slow


We have a Cisco 837 at a customers site.

The customer complained about slow performance.

We tried some alcatel modem and indeed, the Cisco was slower, and pretty much :

Cisco router:

(Tue May 18 2004 om 14:40:19 UTC+0200)

Download : 268.9 KByte/sec

Upload : 41.8 KByte/sec

Connection : 593.0 Conn/min

Ping test Nederland : 15.0 ms

Alcatel modem:

(Tue May 18 2004 om 14:45:46 UTC+0200)

Download : 346.1 KByte/sec

Upload : 59.0 KByte/sec

Connection : 1,209.0 Conn/min

Cisco router:

(Tue May 18 2004 om 15:12:44 UTC+0200)

Download : 278.2 KByte/sec

Upload : 31.9 KByte/sec

Connection : 565.0 Conn/min

Ping test Nederland : 13.0 ms

Alcatel modem:

(Tue May 18 2004 om 15:18:35 UTC+0200)

Download : 365.5 KByte/sec

Upload : 56.7 KByte/sec

Connection : 1,070.0 Conn/min

I've monitored the processor load but that wasn't the bottleneck.

I don't know what to monitor or to troubleshoot to find the origin of the problem.

Should i try another IOS version, change some config or is the Cisco not working properly ?

Thanks in advance,


2 Replies 2

Frequent Contributor
Frequent Contributor

Check for the buffers, or queues and drops in the show interface command. This can give you some idea about the problem. You can try reducing mtu on the ATM interface by giving ip tcp adjust-mss 1452 Remove crypto map from interface Adjusted mtu to 1380, re-apply the crypto map. If these steps didnot work upgrade your IOS to a 12.3 version.

The customer has a dsl connection of

640kbit up and 4096kbit down

I have tried several things.

First upgraded the ios to c837-k9o3sy6-mz.123-7.T1.bin ; without improvement of speed.

Second : I removed the access lists and ip inspect rules ; the result was a higher bandwidth.

Trying a speed test, it went from 38kbyte upload to 50 kbyte upload.

I tested the situation multiple times; with and without access lists and ip inspect rules.

The result is that with the inspect rules and access lists the cisco is REALLY slower.

Is this normal ? I thought the processor capacity of the router would be enough to perform some filtering.

The configuration isn't even that extended.

But it seems like putting some access lists on the router really slows it down.

I tested with 2 different 837 routers. Same results for both.

I find it hard to believe we need a pix for the filtering and an 837 for the modem connection.

I have not adjusted the MTU yet, there are no drops if i do a "sh int atm 0"

yourelement-router#sh int atm0

ATM0 is up, line protocol is up

Hardware is PQUICC_SAR (with Alcatel ADSL Module)

MTU 1500 bytes, sub MTU 1500, BW 640 Kbit, DLY 80 usec,

reliability 255/255, txload 3/255, rxload 50/255

Encapsulation ATM, loopback not set

Encapsulation(s): AAL5 AAL2, PVC mode

10 maximum active VCs, 1024 VCs per VP, 1 current VCCs

VC Auto Creation Disabled.

VC idle disconnect time: 300 seconds

Last input never, output 00:00:00, output hang never

Last clearing of "show interface" counters never

Input queue: 0/224/0/0 (size/max/drops/flushes); Total output drops: 173

Queueing strategy: Per VC Queueing

5 minute input rate 127000 bits/sec, 19 packets/sec

5 minute output rate 10000 bits/sec, 16 packets/sec

850994 packets input, 733298536 bytes, 0 no buffer

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

0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort

740742 packets output, 296495615 bytes, 0 underruns

0 output errors, 0 collisions, 2 interface resets

0 output buffer failures, 0 output buffers swapped out

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