How can I connect one VLAN to two different routers ports? Should I do it, or will be better if I connect switches with each other and then connect one of them into router?
You can, and you should. If the switches are stacking switches then you can even have the ports on 2 separate switches. It's a rather simple port-channel configuration on the router and switch. Cisco has a document explaining this, Configuring EtherChannel and 802.1Q Trunking Between Catalyst L2 Fixed Configuration Switches and a Router (InterVLAN Routing).
interface Port-channel1 switchport trunk native vlan 10 switchport mode trunk no ip address flowcontrol send off ! interface FastEthernet0/1 no ip address ! interface FastEthernet0/2 switchport trunk native vlan 10 switchport mode trunk no ip address channel-group 1 mode on ! interface FastEthernet0/3 switchport trunk native vlan 10 switchport mode trunk no ip address channel-group 1 mode on
And on the router:
interface Port-channel1 no ip address hold-queue 150 in ! interface Port-channel1.10 encapsulation dot1Q 10 native ip address 10.10.10.1 255.255.255.0 ! interface Port-channel1.20 encapsulation dot1Q 20 ip address 10.10.11.1 255.255.255.0 ! !--- Output suppressed. ! interface FastEthernet3/0 no ip address channel-group 1 ! interface FastEthernet4/0 no ip address channel-group 1
If you mean should you use a router to connect two separate switches to each other at Layer 2 then probably not no.
A router is designed to be a gateway between two different layer two domains rather than linking them at Layer 2.
If you want the VLAN on each switch to be a single VLAN spanning both switches then connect them to each other. If you want to use the same VLAN ID to provide two separate VLANs, one on each switch, with different subnets assigned, then sure go via the router.
All that said, you can often make a router bridge two interfaces together, which is effectively making the router ports "switch", as switches are just bridging really. In Cisco land, they call this integrated routing and bridging.