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DPC3825 Non-Stop Network Traffic

I've Been Around
Posts: 1
Registered: ‎04-04-2012

Hello All,


I just had Rogers installed and they installed a DPC3825 modem..  My problem is my Ethernet lights are flashing non-stop and it happens with any device that I plug into it. 


As an example I have a DNS-321 NAS and the link light on the front is blinking really fast and it never stops, but it doesn't do that when plugged into my previous router.


I have worked with all the settings and checked everything..  I plug my devices into the old router and they are all normal..  I plug any device into this router and it flashes non-stop. 


What is this thing doing.. Is this modem defective? It shouldn't be sending traffic all over my network constantly unless the devices attached are actually sending or receiving traffic..

Re: DPC3825 Non-Stop Network Traffic

I'm a Senior Advisor
Posts: 847
Registered: ‎02-16-2011

Bottom line - the modems that Rogers now supplies are garbage. If I were you I would inform Rogers. You would also be wise to continue to use your old router by having the new modem put into bridge mode and forget about the router part of the CISCO DPC 3825 - the wireless range is extremely poor and dropped connections are very common!

Re: DPC3825 Non-Stop Network Traffic

I've Been Here Awhile
Posts: 2
Registered: ‎04-27-2012

I just got the same modem/router and have the exact same issue.


However, it's worse than you think.


(in my case at least) The DPC3825 is forwarding an IPv6 "Neighbor solicitation".  This is a multicast packet that ALL my devices in my home receive!

(using WireShark) I captured 457 of these ICMPv6  packets in 60 seconds out of 625 total (73% of my pc’s idle traffic!).  I’m not totally sure whether these packets are being produced by the router or coming from outside (if I disconnect the cable connection they do stop though…).


Average packet size is 87 bytes, so:

87 bytes X 457 packets / min X 60 min/hour X 24 hours/day = ~55 mega bytes / day

That’s about 1.7 Gigabytes / month!


Let’s face it; if these packets are hitting my/our routers you know **bleep** well it’s hitting our cap. Whether your router can filter these or not, Rogers meter is still running.


I haven't talked directly to Rogers about this yet - not sure who would understand - or care.


Ultimately 2 issues here;

1)      These packets shouldn’t be coming in the first place – which is a Rogers issue. (I’m guessing it’s Rogers own equipment testing IPv6.)

2)      Our router should be blocking them – which is a Cisco issue.


I'll post this offically as well and see what happens.

Re: DPC3825 Non-Stop Network Traffic

I Plan to Stick Around
Posts: 19
Registered: ‎03-10-2012

I just ran wireshark and I do not see this on my 3825. However I am in bridge mode.

Re: DPC3825 Non-Stop Network Traffic

I've Been Here Awhile
Posts: 2
Registered: ‎04-27-2012

Is your modem access light flashing like crazy? I’m thinking of switching to bridged mode myself and plopping my old router back in front of it.

However, it still doesn’t prevent the actual multicast packets from hitting my/our modems. If they make it that far we both know Rogers is counting it on our Cap. (1.7 gig/month I’ve calculated).

Here are two packets (out of the ~500/min) I get;


Packet 1:

Source: 2607:f798:805:f003:221:a0ff:fefb:13e0  

Dest: ff02::<local>

Prot: ICMPv6    

Len: 86 

Info: Neighbor Solicitation for fe80::<local> from 00:21:a0:fb:13:e0


Packet 2:

Source: fe80::221:a0ff:fefb:13e0

Dest: ff02::<local>

Type: ICMPv6   

Len: 86 

Info: Neighbor Solicitation for fe80::<local> from 00:21:a0:fb:13:e0


I know very little about IPv6 but FF02:: prefixed addresses are multicast destinations.  F880:: are local-link addresses, but WireShark still shows it coming from the same MAC address. A MAC address that I do not own.

I did an IPv6 lookup of 2607:f798:805:f003:221:a0ff:fefb:13e0 and found it to be owned by Rogers.

My guess is they are testing IPv6 and like the rest of the world have no idea how to implement it.


I have an icident open now with Rogers but I'm getting the boilerplate "resest config" and "unplug it for 30 seconds"  "tech' support responses.

Re: DPC3825 Non-Stop Network Traffic

I've Been Here Awhile
Posts: 3
Registered: ‎05-02-2012
bmiller i agree with you......

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