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blocked ports?

Tutor

blocked ports?

Is there a list of ports that are blocked by ATT?

outbound ports list:

inbound ports list:

 

Is there a method to have the list modified per customer?

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Message 1 of 10
ACE - Expert

Re: blocked ports?

Maybe this ATT article will help. It says:

 

As noted above, AT&T blocks certain ports that transfer malicious or disruptive traffic to protect our customers and our network. Below is more information about port blocking that is currently in place. We may block additional ports in the future based upon threat assessments.

Port

Transport

Protocol

Direction

Threats

0

TCP

Reserved

Both

Reserved Port

19

UDP

Chargen

Both

Reflective DDOS

25

TCP

SMTP

Outbound

SPAM, Malware

68

UDP

BOOTP

Outbound

DHCP server spoofing

123

UDP

NTP

Both

Reflective DDOS

135

TCP

NetBios

Both

Worms, Malware, Reflective DDoS

139

TCP

NetBios

Both

Worms, Malware

445

TCP

MS-DS SMB

Both

Worms, Malware

520

UDP

RIPv1

Both

Reflective DDOS

1900

UDP

SSDP

Both

Reflective DDOS

3479

TCP

Twrpc

Both

End user device instability

7547

TCP

CWMP

Inbound

End user device instability

61001

TCP

IPDR

Inbound

Data exposure, end user device instability

Port 25 I believe can be unblocked for $49 by requesting it (assuming they still do that).  I don't know if any of the other ports can be requested to be unblocked probably because why would you want any of those unblocked?

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*The views and opinions expressed on this forum are purely my own. Any product claim, statistic, quote, or other representation about a product or service should be verified with the manufacturer, provider, or party.
Message 2 of 10
ACE - Expert

Re: blocked ports?

This table doesn't distinguish between source port blocking and destination port blocking.  NTP, for example, is source port blocked (i.e. a destination port of 123 is allowed to pass, but a source port of 123 is not).  As your outbound traffic goes through NAT translation, the source port will be changed and the traffic will pass, if configured to not go through NAT, then the unchanged source port will be blocked.

 

Award for Community Excellence 2019 Achiever*
*The views and opinions expressed on this forum are purely my own. Any product claim, statistic, quote, or other representation about a product or service should be verified with the manufacturer, provider, or party.
Message 3 of 10
Tutor

Re: blocked ports?

Thank you both.

I was able to find what I needed and used that to get a port I needed opened Smiley Happy

Message 4 of 10

Re: blocked ports?

@rudyg305  How did you do this? What did you do to get your port unblocked?

Message 5 of 10
Tutor

blocked ports?

I don't recall exactly who I spoke with nor the department they were in - it was some time ago.
But I did mange to reach someone at AT&T that understand what I needed and was able to open the ports I needed opened.
I've had no related problem since then Smiley Happy
Message 6 of 10
Contributor

Re: blocked ports?

I have a custom application that ATT seems to want to block after an hour or so ...  its not about configuring a pinhole through the firewall in the router (as it works for a period of time), its not about usage as I have unlimited gigabit over fiber ... it works for awhile and that after a time, my application stops working and I see the port is blocked (not in my router but somewhere on the ATT side).

 

It’s a dance .... I change the port ...it works until it stops, find the port blocked somewhere, change the port in the firewall and the application ..its works for a while ..rinse and repeat ...

Message 7 of 10
Tutor

blocked ports?

That sounds like a completely different issue.
What is the "reason" shown for the drop?
Message 8 of 10
ACE - Expert

Re: blocked ports?

@ackerthehacker, do you have a BGW 210 Gateway?  And if so, what version firmware?

One version of the firmware (1.6.7 if I remember correctly) had an issue where port forwarding would only work for a few hours, then fail.  The fix is to get off that version of the firmware.

 

Award for Community Excellence 2019 Achiever*
*The views and opinions expressed on this forum are purely my own. Any product claim, statistic, quote, or other representation about a product or service should be verified with the manufacturer, provider, or party.
Message 9 of 10
Tutor

Re: blocked ports?

Well it seems there is some inconsistency with what AT&T blocks.

 

This thread focused on ports, but it could be that what is getting blocked is the "application".

When opening up a connection, be it by http, https, or direct from a local application, there are firewall inspections that will happen and many times, regardless of the actual port, the firewall will see an application being used. Sometimes this is by correlating the ports used and the destination, other times is by the actual source or destination application.

AT&T blocks, on SOME towers, PCoIP, which breaks the ability to use VMwares Horizonview.

This is a business application and should not be blocked, as it provides remote access for employees working in the field.

It does not appear the used ports are blocked, but rather an inconsistency in firewall rules applied to the towers/traffic.

 

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