Can’t UNC to SAN (49173 > [SYN] Seq=0 Win=8192 Len=0 MSS=1460 WS=8 SACK_perm=1)

Question

I have a whole subnet on a 3650 that can't UNC in to one of all of my SAN's. When I attempt to UNC in to it using a laptop with wire shark installed I get back the returned black packets:

(49173  >Microsoft-ds [SYN] Seq=0 Win=8192 Len=0 MSS=1460 WS=8 SACK_perm=1)
(49175  >NetBIOS-ssn [SYN] Seq=0 Win=8192 Len=0 MSS=1460 WS=8 SACK_perm=1)
(49174  >http [SYN] Seq=0 Win=8192 Len=0 MSS=1460 WS=8 SACK_perm=1)

What do these mean?

Answer 1

SYN means that the computer sending it tries to setup a connection, and when it's not answered with a SYN/ACK it is retried a couple of times, sometimes on alternate ports depending on the protocol.