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Get the latest news in this issue of the Cisco Small Business Monthly Newsletter

Workaround for SRP500 Issues


** Update **

These and a number of other issues have been addressed in SRP520 MR3.  Please see for details on how to access this code.

There have been a number of reports of the SRP500 becoming unresponsive after a period of use.

Symptoms have included, but are not limited to:

  • DHCP failing
  • No web access to GUI
  • Port forwarding stops
  • DNS proxy fails

Thanks  to all of you that have provided feedback and advice, this had helped  us to isolate the issue, which we are now working hard to fix.   Specifically, remote attacks against the voice ports are causing the  failure of various device services.

In the mean time, it is possible to protect your SRP from these issues by configuring one of both of the following parameters.

Firstly, configure your device to accept only SIP messaging from configured voice services.

To achieve this, log in using the admin user role and select the "Voice" configuration tab.

Select "Line 1" and scroll to "SIP Settings", then set "Restrict Source IP" to yes.

Repeat this configuration for Line 2.

In  addition, if you are not using the voice ports on your SRP, it is good  practice to disable them.  To do this, set "Line Enable" to no for both lines.

One settings have been made for both lines, click on Submit at the bottom of the screen.



Hi Andrew,

I'm a very unhappy owner of a Cisco SRP521W based in New Zealand and I have to say I'm at the end of my patience with Linksys/Cisco. I purchased this model two weeks ago to replace a Linksys WRP400 that was suffering from a constant slow down of internet/WAN speed. I had several opinions from network administrator aquaintances that the WRP400 was bad, so I bit-the-bullet and forked out over NZ$300 for this newer (aparently better) model which after reading the product literature would be the perfect device for our office.

Much to my disgust, I discovered the SRP521W is suffering the exact same symptoms. What's worse, the more I try and find help on the problem, I find that there are many many forum topics raised and that most of the Linksys/Cisco range is suffering the same issues. Can that be true?!

We have been experiencing consistent and gradual WAN speed decreases ever since we've been using your equipment, and it's got to the point now where I've almost been in tears trying to troubleshoot and correct this problem. Enough is enough. We run a small online business, with VoIP and a web/mail/ftp server, and the daily need to be offline for up to 2 minutes (while we switch off then on and wait for the SRP521W which appears to reboot twice) is completely unacceptable. Our customers lose service during their uploads, our phone service is knocked out, and also our rankings with Google suffer with constant "Network Unreachable" errors for our indexed pages.

Here's our setup:

  • 100Mbps symmetrical fibre/cable internet service
  • Cisco SRP521W with:
    • 1 LAN port for a web/mail/ftp server for our small online business
    • 1 LAN port for an 8-port switch for our office network (up to 5 computers connected)
    • 1 Phone port used for VoIP services through WorldxChange (NZ) Ltd. (I have confirmation through WxC that their remote provisioning has RESTRICT SOURCE IP set to YES).
    • 1-2 devices connected to WLAN at any one time.

(Note: we previously had the same setup with the WRP400)

Here's a description of our problem:

After a reboot the SRP521W will function at full WAN speed of about 90Mbps/86Mbps down/up. After about 5 hours uptime, the next speed test will yield about 77Mbps/68Mbps. After about 10 hours uptime, 64Mbps/62Mbps. After 28 hours uptime, we are down to 27Mbps/30Mbps. And it keeps going down from there until we eventually get pissed off with slow (or no existent) online services - usually a day or two. WLAN users also notice a drop off in throughput as the WAN speed drops, and the VoIP quality suffers too after about 48 hours uptime - if we leave it that long.

The reason I now know that this is a Linksys/Cisco problem is because I have swapped the SRP521W for a cheap TP Link router that I borrowed, and after 3 days of use, there has been NO LOSS OF WAN SPEED.

So, this message is literally a plea for help. Cisco PLEASE PLEASE PLEASE help us sort this out. We're sick of spending money and sick of waiting for you.

Mike Walen


Hey Mike,

I don't think I'm going to  waste my time looking at the Cisco SRP-521W as a replacement for the  WRP-400. Maybe it time to accept that an "all-in-one device" is not the best solution, at leaset not from Cisco right now. I have heard of way too many open issues in this forum and others that are not getting anyone's attention at Cisco.

As a VoIP  services provider I can't afford the customer frustration and downtime. I  think I'm just going to go back to a good low-end Router/Firewall/WiFi  device like the SonicWall TZ-100W and keep the ATA out of the router. There are plenty of good ATAs on the market that work well as SIP and/or IAX connections.

I welcome your  comments on another $200-$400 USD price range Router/Firewall/WiFi device  (Cisco or other) that has good control over QoS for VoIP traffic and  bandwdith management. I would also like my ideal small office router to  have SNMP.

Nicky Smith, President

+1-336-544-4000 Ext 105

Cisco Employee

Hi Mike,

Thanks for your comments.  I'll make our release candidate for MR3 available to you now.  This includes many fixes for issues that you and customers like you have been seeing over the last six months.  I hope you find that this improves your experience with this product.




Hi Andrew,

We're eagerly trying 1.01.19 RC now on our SRP521W and will report back in a few days with some results. Thanks for your response, it's really appreciated.

Kind regards,

Mike Walen.


Hi Andrew,

Well we've tried the 1.01.19 RC firmware for over 30 hours now, and while there is a small improvement, I don't think it's there quite yet. Below is a section from a table that I have been updating regularly with my findings. Although we're experiencing the slow down just like always, it seems to be bottoming out at around 55Mbps Down/Up, whereas previously we'd be down to about 30Mbps and it would still be decreasing (to eventually become unresponsive).

Although we're getting 55Mbps, consistently at this stage, we're noticing that online services (e.g. web browsing, streaming video, downloading large files) are not snappy and quick like they are after a reboot but are still sluggish and slow (almost like we're on an ASDL connection despite having a 100Mbps fibre connection).

DateTimeRouter UptimeD/loadU/loadPing

As you can see from the table, the speeds start off excellent, then slowly decrease down. We will continue to use this RC firmware, but as you can appreciate, this is still well below our expectations and what we require from this device.

We have about a week left before I will have to return the SRP521W to our supplier for a refund and begin the search for another suitable router so I REALLY hope something big happens in that time

If you require more information about our setup or configuration, please don't hesitate to contact me.

Mike Walen


Hi again Andrew,

Well, we've been using the 1.01.19 RC firmware for 4 days now and I am unimpressed again. I noticed our router mysteriously return to high-speed on two mornings now, which was great, but it made me curious and a little suspicious as to why it suddenly went back up from being so slow.

From what I can tell, the 1.01.19 RC firmware upgrade is basically a script that reboots the router every 48 hours.

I can't see any reference to this feature in any of the GUI menus, mainly because my VoIP provider has remote provisioned and locked down the admin side of things, but I can clearly see the router is rebooting every second day at 5:30am (which is when I installed the RC firmware) just by looking at the up-time clock in the status section.

Now I can't speak for anyone else using a SRP500 series router, but this is literally a poor bandaid to cover the real problem(s). As mentioned in a previous post, we host an in-house web/mail/ftp server behind the router and rebooting of the SRP521W (at any time of the day) means a loss of service to our customers and is completely unacceptable.

So, all I can say now is good luck in fixing the SRP500 series (and the WRP400) routers Cisco. I'm returning our SRP521W back to our supplier and looking for a better option.

All the best.
Mike Walen.

Hello. I apologize for imperfect English. My router also has problems with speed. In version 01.19RC not noticed until now voip termination. Earlier in the downlink as 01.11 voip interrupted. I hope that Cisco will improve the firmware to make it perfect. Because the router was very expensive and unfortunately, this translates into quality. Regards Arthur.

Cisco Employee

Hi Mike,

Many thanks for your feedback and specifically the details of the throughput degradation.  Before your report, I hadn't been aware of this, but will certainly commence an investigation now (I regret that this will be too late for you now).

I will also make a point of understanding why the performance bounces back every couple of days - there is no reboot script in this release (although there may be some monitoring processes that periodically clears up unused resources).

Best Regards,

Andy Hickman

Hello. Please note the CPU usage before and after the restart. Regards Arthur.


We have just upgraded to the SRP 527W router because of the scalability of services on offer. Currently we are not using it for VOIP at all, but without fail since we installed afetr around 24 hours/48 hours after a reboot the Wireless network mysteriously is unconectable which suggests DHCP failure and also there is no access to the GUI via or a specifically set up address of

The only option to get round this issue is to reboot every 48 hours which is completely unacceptable. There is not even an option within the GUI to upgrade firmware either in the admin screen.

I take it this is a known issue now, but what is the solution to:

- DHCP failure

- No access to Web GUI

I thought this was going to be the router that ends all of our problems and lets us get on with business, but it looks like i was wrong.

Cisco Employee

Hi Malcom,

Which firmware are you using?  The two symptoms that you describe are characteristic of the issue described initially in this thread.  Have you configured the work around setting? (it doesn't matter whether you use voice or not, the workaround would still be required).

Also, as mentioned above, this issue is fixed in MR3 (I'll post a copy of the release candidate for you if you wish to try it in advance of formal posting on

Please let us know (via this thread) if you continue to have issues following either configuration of the work around, or upgrading to the MR3 release candidate.



Cisco Employee

Thank you Artur,

It's not unusual to see the CPU spike from time to time - especially on intially boot.  Are you saying the the CPU stays at 99% for a long time?

Is this using the MR3 release candidate code?

We will investigate the throughput degradation issue this week.



Model:SRP527W, ADSL2+ AnnexA, 802.11n ETSI, 2FXS/1FXO
Version ID:V01
Hardware Version:4.0.0
Boot Version:1.1.17 (Jan 4 2010 - 21:15:46)
Firmware Version:1.01.09 (001) Apr 7 2010
ADSL Firmware Version:0.41.0
Recovery Firmware:1.01.09 (001)
Setup Wizard Version:1.01.09 (000)
WAN MAC Address:
Current Time:Mon, 31 Jan 2011 14:00:21

Thank you for the release files, I have sent you an email with a question regarding this.


Dear Andrew. My router firmware is version 01.19 MR3 RC. As you've seen the peak occurs all the time downloading the file. Then it drops performance. The processor achieves almost 100% load. After the restart downloading the same file and then it's full capacity. Then, the CPU load reaches 50% all the time downloading the file.Please note the speed. Before the reboot is wrong. After a reboot everything returns to normal for several hours.Please click on my images. My post earlier in this thread.The first picture when you reboot. The second image before rebooting the router.The difference can be seen very clearly.


I have been checking with our test devices looking for the slow down, Micheal you are a customer of ours, the device you have resyncs every 48 hours on it's config profile.

I am running the same unit on a test Fibre circuit running a 30/6 Mb profile have been running this for 3 almost 4 days and no impact on throughput that I can see, Voice operation, downloading via LAN and wirelesss are running at peak.