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hi guys,

if i want to connect from client to an application server on TCP port 135 (and the port is open on the server) but let's say there is a security device along the way from client to server that will block TCP port 135 it will not allow to establish the connection, right ?

Thank you for clearing my doubts !

asked 11 Dec '15, 02:00

adasko's gravatar image

accept rate: 0%

Yes. That's what ACLs (Access Control Lists) and Firewalls do. Depending on the blocking mechanism you will either see a "blocked" result or a "rejected" result. The difference is that for "block" you'll not see any kind of answer to your connection attempt, while "reject" will tell you that you're not allowed to access that port. Firewalls usually "block" to avoid being detected/tested - your connection simply fails but you cannot easily tell who blocked the packet.

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answered 11 Dec '15, 02:57

Jasper's gravatar image

Jasper ♦♦
accept rate: 18%

Thank you Jasper for your clear answer ! out of curiosity, is it common to block TCP port 135 ?

thank you

(11 Dec '15, 03:06) adasko

On perimeter firewalls (meaning: the ones at the edge to the internet): yes, absolutely. Internal firewalls may or may not do this, depending on the network segmentation and security requirements.

(11 Dec '15, 05:55) Jasper ♦♦
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question asked: 11 Dec '15, 02:00

question was seen: 1,354 times

last updated: 11 Dec '15, 05:55

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