Fiber-optic connection between two routers is always off, regardless of any configuration

Question

I have modeled the following network on packettracer. The fiber-optic connections between Router4 and Router8 is down and doesn't get up. Whatever I do, the connection remains off. The source file of the model is uploaded here. I wonder if anybody knows why the connection is off.

---

I add running configuration of routers here. Running configuration of Router4:

Router#show running-config 
Building configuration...

Current configuration : 1009 bytes
!
version 12.2
no service timestamps log datetime msec
no service timestamps debug datetime msec
no service password-encryption
!
hostname Router
!
!
!
!
ip dhcp excluded-address 192.168.16.1
!
ip dhcp pool POOL
 network 192.168.16.0 255.255.255.0
 default-router 192.168.16.1
 dns-server 172.16.100.2
!
!
!
ip cef
no ipv6 cef
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
interface FastEthernet0/0
 ip address 192.168.16.1 255.255.255.0
 duplex auto
 speed auto
!
interface FastEthernet1/0
 no ip address
 duplex auto
 speed auto
 shutdown
!
interface Serial2/0
 no ip address
 clock rate 2000000
 shutdown
!
interface Serial3/0
 no ip address
 clock rate 2000000
 shutdown
!
interface FastEthernet4/0
 ip address 192.168.0.2 255.255.255.0
!
interface FastEthernet5/0
 ip address 10.0.4.1 255.255.255.0
!
router rip
 version 2
 network 10.0.0.0
 network 192.168.0.0
 network 192.168.16.0
 no auto-summary
!
ip classless
!
ip flow-export version 9
!
!
!
!
!
!
!
line con 0
!
line aux 0
!
line vty 0 4
 login
!
!
!
end

Running configuration of Router 8:

Router#show running-config 
Building configuration...

Current configuration : 1057 bytes
!
version 12.2
no service timestamps log datetime msec
no service timestamps debug datetime msec
no service password-encryption
!
hostname Router
!
!
!
!
ip dhcp excluded-address 192.168.137.1
!
ip dhcp pool POOL1
 network 192.168.137.0 255.255.255.0
 default-router 192.168.137.1
 dns-server 172.16.100.2
!
!
!
ip cef
no ipv6 cef
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
interface FastEthernet0/0
 ip address 192.168.137.1 255.255.255.0
 duplex auto
 speed auto
!
interface FastEthernet1/0
 no ip address
 duplex auto
 speed auto
 shutdown
!
interface Serial2/0
 no ip address
 clock rate 2000000
 shutdown
!
interface Serial3/0
 no ip address
 clock rate 2000000
 shutdown
!
interface FastEthernet4/0
 ip address 10.0.1.2 255.255.255.0
!
interface FastEthernet5/0
 ip address 10.0.2.1 255.255.255.0
!
interface GigabitEthernet8/0
 ip address 10.0.4.2 255.255.255.0
!
router rip
 version 2
 network 10.0.0.0
 network 192.168.137.0
 no auto-summary
!
ip classless
!
ip flow-export version 9
!
!
!
!
!
!
!
line con 0
!
line aux 0
!
line vty 0 4
 login
!
!
!
end

Answer 1

There is a mismatch in speed between Router4, Fa5/0 and Router8, Gi8/0. Router8 Gi8/0 was configured with a Gbit GBIC module, which was connected to a 100 Mbit FX GBIC module. The mismatch caused the connectivity problems.