I believe you have a duplicate IP.In your first post you said "NMS-Server (10.10.0.99)" But the config of your switch shows:interface vlan 20
name VL20_DMZ
ip address 10.10.0.99 255.255.255.0 If this is correct, you've configured your switch with t...
Have you set a default gateway on the switch? In this case it should be set to the IP address of your firewall on the 192.168.1.0/24 network, or 192.168.1.1. Its happened to me a few times to forget adding that in!
Here's the KB for 2960X - https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst2960x/software/15-0_2_EX/network_management/configuration_guide/b_nm_15ex_2960-x_cg/b_nm_15ex_2960-x_cg_chapter_0100.html#task_BBC527F034B94EB1BFE37A4E219952DD Prett...
Any specific reason you've chosen to back up to your own tftp server? As @balaji.bandi mentioned above, there's a few commercial and open source solutions that have solved this problem already. It comes down to a bit of time vs. money / build vs. buy...