Sorry for the newb question, I am trying to figure out how to best link up an subinterface on a Cisco 1921 router, with an external network, by connecting the router and the cable from the external network, to a Cisco Catalyst 2960 switch and isolating them into their own VLAN. The external network recommended I use a 172.A.A.102 255.255.252 for my router IP, and ping 172.A.A.101 on their network. I was able to ping successfully by connecting the external network's cable to my laptop and configuring their IP information, but I cant ping from my router after what I setup:
I created the subinterface for the external network on my router with:
interface GigabitEthernet0/0.3 encapsulation dot1Q 802 ip address 172.A.A.102 255.255.255.252
On the switch I configured two ports: f0/5 for the router, and f0/6 for the external network cable with:
But unfortunately I cannot ping 172.A.A.101. Please what am I doing wrong?
interface FastEthernet0/5 switchport mode trunk spanning-tree portfast !
interface FastEthernet0/6 switchport access vlan 802 switchport mode access spanning-tree portfast