Cisco 877 not getting full ADSL speed?

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Hi everyone, thanks for all the input! I have now got to the root of the problem! But could still use a little help!

The issue is with the BVI interface

When I do not have a bridge interface assigned, and am using a cable connection in VLAN 2, with Interface VLAN 2 set up as the NAT inside interface, I get 13.5mb throughput.

However as soon as I move the IP address and NAT statments to the BVI interface and add the VLAN interface to the bridge group, the speedtest result is reduced to 9.5mb. This speed is the same on the LAN and WLAN connections.

The question is... why?! Is the router maybe not capable of converting over the bridge at the speed I need?

I'm pleased to have identified the cause of this

And for info, I also set up an 877 router at work thats not wireless and it achieves 17mb downstream, so that proves these routers are capable

Cheers
Tim

 

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Good work, Tim!

 

Hi all,

Well I reconfigured the router, so that I had a differnet VLAN on the LAN and WLAN. I scrapped the BVI interfaces, and instead gave the dot11 sub-interface an IP address, and made it a IP NAT inside interface. I did the same with the LAN VLAN interface

And I thought this was the end of it, but... sadly not!

Now if I run a speedtest using a cable onto the LAN VLAN, I get 13.8mb in Speedtests - NICE!

But from the wireless, I STILL only get 9.5mb

I am stumped once again. The CPU utilisation is still quite high (95%) during a Speedtest, if thats an indicator?

Thanks
Tim

 

The CPU's gotta decrypt those wireless packets as they come in. I'm guessing that's at least part of the issue.

 

This is true, however I turned off all encryption and the results were the same

 

Is the channel clean? If not, the router is having to listen to traffic from all those other sources that are broadcasting on that channel.

Plus, how many devices do you have on your network associating with the router? They generate traffic as well... all things to consider in a wireless environment.

 

Haha is this how the CCNAs roll

 

I am not totally sure how to get the router to choose a clean channel.... When I turn on the Dot11 interface it says its scanning for a suitable frequency, is this looking for the cleanest one?

I have been testing with just 1 device associated

What do you mean? Are you implying I should know this because I have sat a CCNA?

 

I am not certain, but I am fairly sure that you can statically assign the channel that it uses.

In any case, you'd have to sniff to see how congested the other channels are. I've used Netstumbler in the past.

 

channel XXXX <- (Center Frequency )

http://www.cisco.com/en/US/docs/routers/access/1800/wireless/configuration/guide/s37chan.html

 

Something to check - you mention cpu usage is 95%, but what process is responsible?

Use "sh proc cpu sort 5sec" and see what process is eating up cpu time.

Also, you can use "sh dot11 int" to see statistics, in particular look at the last 5 seconds data, while testing transfer rates. Clear the stats just before a test to get a good picture as well.


Spice Weasel

 

having seen the 12Mbps throughput limitation on a few sites, I just thought i'd comment that the 877 is capable of more than that

Code:

                 DS Channel1      DS Channel0   US Channel1       US Channel0
Speed (kbps):             0            19043             0              1023
Cells:                    0        225694765             0         513143799
Reed-Solomon EC:          0             5898             0                 0
CRC Errors:               0             1804             0                 0
Header Errors:            0             1654             0                 0
Total BER:                0E-0           1235E-8
Leakage Average BER:      0E-0           7458E-10
Interleave Delay:         0               23             0                 0

Have been downloading a 10gb file, and getting sustained 15MBps, CPU is showing

Code:

CPU utilization for five seconds: 69%/66%; one minute: 63%; five minutes: 63%

And just some of the other stats for completeness really

Code:

Alcatel 20190 chipset information
                ATU-R (DS)                      ATU-C (US)
Modem Status:    Showtime (DMTDSL_SHOWTIME)
DSL Mode:        ITU G.992.5 (ADSL2+) Annex A
ITU STD NUM:     0x03                            0x2 
Chip Vendor ID:  'STMI'                          'GSPN'
Chip Vendor Specific:  0x0000                    0x0010
Chip Vendor Country:   0x0F                      0xFF
Modem Vendor ID: 'CSCO'                          'GSPN'
Modem Vendor Specific: 0x0000                    0x1000
Modem Vendor Country:  0xB5                      0xFF
Serial Number Near:    FHK13012268
Serial Number Far:     
Modem VerChip ID:        C196 (0)
DFE BOM:         DFE3.0 Annex A (1)
Capacity Used:   99%                             100%
Noise Margin:     5.5 dB                         12.0 dB
Output Power:    20.0 dBm                        12.5 dBm
Attenuation:     23.0 dB                          8.0 dB
Defect Status:   None                            None                        
Last Fail Code:  None
Watchdog Counter: 0xE9
Watchdog Resets: 0
Selftest Result: 0x00
Subfunction:     0x00 
Interrupts:      8289 (0 spurious)
PHY Access Err:  0
Activations:     1
LED Status:      ON
LED On Time:     100
LED Off Time:    100
Init FW:         init_AMR-3.0.014_no_bist.bin
Operation FW:    AMR-3.0.014.bin
FW Source:       embedded
FW Version:      3.0.14

 

Sorry to bump a semi-old thread, but is the conclusion here that the 877w can support the higher speeds of ADSL2+?

I saw ADSL2+ and Cisco and just sort of presumed it would...

My Thomson router from O2 is currently synced at 14,405/1,325 (it's normally a bit higher, but the router is slowly dying, hence the replacement), and the throughput is usually very near the sync speed. I'm only planning to use it at home with no more than three users connected at once, but it'd still be nice to get the speeds I pay for!

 

ADSL 2+ is still very much dependant on the distance you are from your exchange and more specifically your ISP's DSLAMS. Contact your ISP if you think your not getting the speeds you should, there are many tweaks that could improve things for you.

 

Sorry for not responding to my own thread.

In the end I gave up. The Cisco 877 is definitely capable of up to 22mb (I've set up a few recently on 20mb circuits). It suffers with the wireless part - for some reason the wireless cannot get the speed.

If you are using a Ethernet cable you will get the speed.

So maybe you need a Cisco 877 (non wireless), and another brand wireless AP?

Tim

 

Sorry, what I meant was, I get ~15Mbps on my Thomson box, would I get that on a Cisco 877w or is it limited to 12Mbps?

I'm quite happy with the speed that I'm getting at the moment, but the router needs replacing. I just wanted to make sure that the Cisco 877w wouldn't have any sort of bottleneck, and that I'll get the maximum speed my line supports.

 

I would say you will get the full 15mpbs, but only about 10 will get to your machine over wifi. Any cabled connection will get the full 15

 

Just saw this, perfect.

The house is wired with Cat5e anyway, and there are two additional access points (lead lined chimneys + Victorian walls = wifi fail) in the house, so as long as the wired throughput is good, I'm happy.

It's just a shame Cisco don't do any integrated services routers with built in gigabit switches. I might even end up going for a Linksys/Billion.

 

That's the nature of wireless... encryption and CSMA/CA will lower the amount of throughput you're gonna get.

 

Although my Netgear router manages it without any hassle!!