Cisco 800 series issue

By jason.sincock ·
Hi all,

I have an issue with an 800 series router.
We are using it as a backup connection for our email.
When I created a nat for the emails to come through, normal emails
would come through fine but any emails with an attachment on it
would be blocked.
In theory it should work because it still has the normal connection to
use and the cisco's connection as backup.
I am wondering if there is a setting that limits the size of traffic
coming through?
Your help is greatly appreciated.

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All Answers

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Yes and no

by Fregeus In reply to Cisco 800 series issue

Yes there are commands that will limit the traffic going through your router. But no, that command will only restrict the flow of traffic, not the quantity. To your email would get through, just slower. Your cause is somewhere else.


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Further help

by jason.sincock In reply to Yes and no

Any idea where that cause is?

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by Fregeus In reply to Further help

I can tell you that i doubt very much that the network is the culprit. My guess (from experience) would be possibly an antivirus, antispam or firewall system that withholds the attachments for some reason. specially if the mail itself, without the attachement, gets to the destination.

So I would do a thorough investigation of all step needed for mail to get in and see which system has the ability to withhold part of the message (ie the attachement).


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by Jellimonsta In reply to Cisco 800 series issue

Do you have NBAR enabled on your ISR 800 router?
Or do you have CBAC rules that are inspecting Email and attachments on the router?

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Still denying attachments

by jason.sincock In reply to NBAR

I checked this and the IOS on the router doesn't have NBAR.
I checked CBAC rules and none are configured.

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Issue found

by jason.sincock In reply to Still denying attachments

For those who are interested,
we changed the router with a modem and found the issue
still there so it looks like a problem with the mtu of the line.

Thanks for the help

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