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Hi, We have a scenario like my end LB is sending SYN message and from the far end it is sending ACK message instead of sending the SYN,ACK, and again LB end it is re-transmitting the packet.

Can you please help me why far end device/server is sending ACK message directly to SYN message instead of SYN,ACk, what could be the issue does we need to check at our LB side or far end server side.

Thank You, Suresh

asked 12 May, 06:57

Suresh%20Jothi's gravatar image

Suresh Jothi
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Suresh-

Are you sure the ACK is in response to the SYN and not an ACK to other data?

Do you have a complete trace?

Is it possible the far-end is not performing a 3-way handshake but trying to send discrete SYN and ACK messages in response to the initial SYN as diagrammed in RFC 793 on page 27? NOTE: I've never (EVER) seen a device do this but just speculating.

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answered 12 May, 07:07

dbAtAffirmed's gravatar image

dbAtAffirmed
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Suresh- I saw your trace (not sure why it doesn't show up here)... The far end looks quite broken. If you are not already running the capture on that device I would suggest you run it there (103.16.101.51) to get its point-of-view to ensure there isn't anything funny going on. /dave

(16 May, 08:13) dbAtAffirmed
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question asked: 12 May, 06:57

question was seen: 291 times

last updated: 16 May, 08:13

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