# ISP says i have a loop.

## arndawg

Hi. My ISP say we have a loop and that's why we have unstable internet connection. They gave me a mac adress and that was the WAN port of my firewall. So i changed that networkcard but the problem happend again and the ISP gave me the mac-adress of that new networkcard. So i'm guessing it's something on my network. I have 30 VLANS through the WAN (From isp)port so i'm guessing it's something from there, but i don't know how to find such a thing. 

I'm using gentoo, iptables, iproute2 and vconfig. I'm totally clueless. I tried using Snort to perhaps locate anything wierd but i'm not sure what i'm looking for. 

Any help GREATLY appriciated.

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## tylerwylie

Are you watching broadcast traffic on  your WAN interface? that could be what's causing that.

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## arndawg

 *tylerwylie wrote:*   

> Are you watching broadcast traffic on  your WAN interface? that could be what's causing that.

 

Not quite sure how. Any magical command?    :Embarassed: 

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## tylerwylie

Check tcpdump, if you're sending out excessive broadcasts that could be what they are talking about.

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## arndawg

 *tylerwylie wrote:*   

> Check tcpdump, if you're sending out excessive broadcasts that could be what they are talking about.

 

thanks. installing it now.

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## arndawg

Ok.  On one vlan interface i get this:

 *Quote:*   

> 14:04:30.358007 IP 169.254.190.22.netbios-ns > 169.254.255.255.netbios-ns: UDP, length 50
> 
> 14:04:31.096143 IP 169.254.138.172.netbios-ns > 169.254.255.255.netbios-ns: UDP, length 50
> 
> 14:04:31.858514 IP 169.254.190.22.netbios-ns > 169.254.255.255.netbios-ns: UDP, length 50
> ...

 

Does anyone know what this means? I think that's strange.

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## tylerwylie

That's a good bit of netbios traffic all destined for a local fallback(169.254)  IP address. Got any windows machines on there?

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## arndawg

 *tylerwylie wrote:*   

> That's a good bit of netbios traffic all destined for a local fallback(169.254)  IP address. Got any windows machines on there?

 

6 windows machines, nothing else except 3 switches.

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