After replacing an SRX device, management access (SSH/Telnet) to the fxp interface stopped working, even though basic connectivity (ping) was successful.

SSH/Telnet to SRX fxp interface fails. 

Ping works normally

SRX unable to SSH to the directly connected switch:

• SYN received on SRX
• SYN-ACK sent from SRX
• SYN-ACK not received on switch (EX)

Interface flap on switch or Removing firewall filters on SRX and EX does not help. 

Identified that Dot1x authentication was enabled on the Switch port 

After SRX replacement, the new device details (MAC/SN) were not updated in the authentication server

 

Fix options:

• Workaround - Disable Dot1x on the switch port
• Update the authentication server with the new SRX device credentials.