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strange network issue

Last response: in Networking
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April 11, 2013 6:04:45 AM

Hi,

I have this strange problem with my network and was wondering if anyone might be able to help me out.

Here is my topology:
I have an ADSL modem router (Netcomm NB1300plus4) connecting to the Internet. It's assigned with a static Public IP address.

From my modem router, it is connected to both my mail server and a Netgear router FVS318. Both my mail server and Netgear router are assigned with static Public IP address because I have a block of 8 subnet IP addresses: 69.xxx.xxx.xxx/29 and subnet mask: 255.255.255.248

Then, all my LAN network are sitting behind the Netgear router.

The strange problem I'm getting is that most of the time when I can't access to my mail-server from home (outside my office), I have to reboot my Netgear router. Then, everything is working again. I find this bizarre because the one that I should reboot is the modem router, not the netgear router.

This happens quite regularly which worries me a lot because it causes problem for my staff to be able to check their mails from outside the LAN.

When it happened for the first time, I thought I lost the Internet connection which might be the reason I could not connect to my mail-server from home so I came to the office to restart my modem router (Netcomm). This did not do the trick as I still could not access to my mail-server.

Then, I tried to reboot my Netgear router by accident. To my surprise, everything seemed to work again. I could log into my webmail from both office and home.

I wonder why the problem (if any) with the Netgear router could affect the Internet connection to my mail-server which sits outside the Netgear router.

Any help would be greatly appreciated.

Thank you very much

More about : strange network issue

April 11, 2013 8:46:26 AM

it almost sounds like your Netgear router is creating large traffic to the modem.

is there a switch connected to the Netgear?

can you still communicate to the Netgear and the LAN when it happens?

does it happen at random times? Is there a pattern to the madness?
April 11, 2013 6:57:35 PM

Thank you for your reply.

Emerald said:
it almost sounds like your Netgear router is creating large traffic to the modem.
Yes, I agree with you but unable to figure out what's causing it.

is there a switch connected to the Netgear?
Yes, there is a couple of old switches (unmanaged ones) connecting to the Netgear router

can you still communicate to the Netgear and the LAN when it happens?
Not at all. I tried to access to it by typing into my web browser \\192.168.0.1 and I waited too long until I got connection error.

does it happen at random times? Is there a pattern to the madness?
Yes, you're right. sometimes it works for a week or two, and other times it can work only for a couple of days before it happens again.


This drives me up to the wall. Thank you so much in advance
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April 11, 2013 9:17:26 PM

You do have the Netcomm configured in full bridge mode, NOT as a router, correct?
April 11, 2013 10:40:51 PM

Thanks for your reply.

eibgrad said:
You do have the Netcomm configured in full bridge mode, NOT as a router, correct?

No, I have the bridge mode disabled on Netcomm.

Just to give you more info on my Netcomm configuration, I have the bridge mode disabled, the NAT disabled and DHCP server disabled. My mail server sits behind the Netcomm as I mentioned before and it's been assigned with static Public IP address.

Thank you
April 11, 2013 10:51:57 PM

Well that's sounds like a problem. If the Netcomm is configured as a router, and the WAN of the Netcomm and the devices behind it are using the same network (69.xxx.xxx.xxx/29 and subnet mask: 255.255.255.248), that makes routing ambiguous. You only use routing when the WAN and LAN are supporting different networks. If they're the same network, then all devices on the Netcomm should simply be bridged/switched, not routed.

In fact, if it was me, and the Netgear supported it, I’d also probably use one-to-one NAT and place the mail server behind the Netgear router (to take advantage of its firewall, and simplify the configuration). So now the mail server has a local IP behind the Netgear, put appears to have its own public IP to the outside world (separate from the other public IPs).

But at the very least, it seems to me the Netcomm should be bridged.

April 11, 2013 11:39:27 PM

eibgrad said:
Well that's sounds like a problem. If the Netcomm is configured as a router, and the WAN of the Netcomm and the devices behind it are using the same network (69.xxx.xxx.xxx/29 and subnet mask: 255.255.255.248), that makes routing ambiguous. You only use routing when the WAN and LAN are supporting different networks. If they're the same network, then all devices on the Netcomm should simply be bridged/switched, not routed.

In fact, if it was me, and the Netgear supported it, I’d also probably use one-to-one NAT and place the mail server behind the Netgear router (to take advantage of its firewall, and simplify the configuration). So now the mail server has a local IP behind the Netgear, put appears to have its own public IP to the outside world (separate from the other public IPs).

But at the very least, it seems to me the Netcomm should be bridged.



Ok, now I understand it, thank you eibgrad for your support and your advice.

I'd enable the bridge mode on my netcomm given that all devices sitting behind it are on the same subnet 255.255.255.248

Thank you for enlightening me.
April 12, 2013 12:15:29 AM

Btw, it's not clear whether this issue of routed vs. bridged explains the behavior you're experiencing. It might not. But when you have this kind of configuration error, there's no telling what goofy behavior it may generate. So it's still important to make sure that we don't make the situation worse because of some obvious misconfiguration.
April 12, 2013 5:45:27 AM

I avoided this question because I think he is using a router that in effect allows it have a subnet assigned to the wan port. So unlike most routers I deal with where you have a wan block and then route the private block to the routers WAN address this device somehow assigns all the address the wan adapter. I almost pulled my hair out helping someone with a router like this, it is very different. Maybe someone who has used one of these routers is reading this and can help.
April 12, 2013 9:27:53 AM

I see what you're saying.
April 13, 2013 4:22:41 AM

eibgrad said:
I see what you're saying.


Thank you for your reply.

hmmm... sounds like I have a very strange router issue here indeed.

Anyhow, What I'll do for now is to configure it correctly on my Netcomm modem router by turning on the bridge mode so that it'll act as just a modem at least. Then, I'll wait and see what happens from here.

Worse comes to worst, I just need to change to Netgear FVS318G prosafe or FVS318N. And perhaps, using the same brand Netgear for my ADSL modem router in replacement of my Netcomm modem router.

Thank you so much for your help. I'll update you how it goes.
!