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Steve_Carroll_1's avatar
Steve_Carroll_1
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Dec 04, 2014

Why is my F5 dropping telnet on port 25 for one network?

I have configured SMTP on my LTM (11.4.1) and have configured a SNAT of 10.229.104.37 so all connections from the LTM are sent with this address and I have no iRule configured.   If telnet 10.229....
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Steve_Carroll_1's avatar
Steve_Carroll_1
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I have resolved the issue and it seems that the previous F5 engineer put a packet filter on the LTM for port 25 and some networks.

 

However, the network in question was not in the allowed list. There was also a deny list for port 25. Also logging was disabled on both filters.

 

I've added the network to the allow packet filter and it now connect.

 

PT2012_73791's avatar
PT2012_73791
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Jun 04, 2015
Hmmm. Glad you posted the answer. Same problem on a new SMTP VIP. Funnily I imagine it was on the same chassis. I can't see why logging on a filter would ever want to be disabled. It makes trouble shooting very hard.