Ip cisco phone goes down - packet tracer?

Question

Cisco

I am doing a lab at the Cisco rate and the task is how to find why the IP phone from the 1st network constantly drops and goes down? in a minute, registration starts again and everything works, as soon as you call another IP, the phone drops again. I haven't found the problem yet, can anyone help? I thought about loops in the network, but there are no loops, everything is divided by Vlan 10 data and 20 voice. The only thing I tried was to turn off the third router on the network, and everything works fine, but it’s not clear which side it interferes with. What methods can be used to find a problem on the network?

configs
1 router

spoiler

hostname R2
ip dhcp excluded-address 10.0.0.1 10.0.0.10
ip dhcp excluded-address 10.0.1.1 10.0.1.10
ip dhcp pool VOIP_DHCP
 network 10.0.1.0 255.255.255.0
 default-router 10.0.1.1
 option 150 ip 10.1.1.1
 dns-server 10.0.1.1
ip dhcp pool COMP_DHCP
 network 10.0.0.0 255.255.255.0
 default-router 10.0.0.1
 dns-server 10.0.0.1
interface GigabitEthernet0/0
 ip address 192.168.0.2 255.255.255.0
interface GigabitEthernet0/1
 no ip address
interface GigabitEthernet0/1.10
 description Comp
 encapsulation dot1Q 10
 ip address 10.0.0.1 255.255.255.0
interface GigabitEthernet0/1.20
 description VOIP
 encapsulation dot1Q 20
 ip address 10.0.1.1 255.255.255.0
ip route 0.0.0.0 0.0.0.0 192.168.0.1 
!

2 router

spoiler

hostname R1
ip dhcp excluded-address 10.1.0.1 10.1.0.10
ip dhcp excluded-address 10.1.1.1 10.1.1.10
ip dhcp pool VOIP_DHCP
 network 10.1.1.0 255.255.255.0
 default-router 10.1.1.1
 option 150 ip 10.1.1.1
 dns-server 10.1.0.1
ip dhcp pool COMP_DHCP
 network 10.1.0.0 255.255.255.0
 default-router 10.1.0.1
 dns-server 10.1.0.1
spanning-tree mode pvst
interface FastEthernet0/0
 ip address 192.168.0.1 255.255.255.0
interface FastEthernet0/1
 no ip address
interface FastEthernet0/1.10
 description Comp
 encapsulation dot1Q 10
 ip address 10.1.0.1 255.255.255.0
interface FastEthernet0/1.20
 description VOIP
 encapsulation dot1Q 20
 ip address 10.1.1.1 255.255.255.0
interface FastEthernet1/0
 ip address 192.168.20.1 255.255.255.0
interface FastEthernet1/1
 no ip address
router rip
ip route 0.0.0.0 0.0.0.0 192.168.0.2 
ip route 0.0.0.0 0.0.0.0 192.168.20.2 
telephony-service
 max-ephones 24
 max-dn 48
 ip source-address 10.1.1.1 port 2000
ephone-dn 1
 number 101500
ephone-dn 2
 number 101502
ephone 1
 device-security-mode none
 mac-address 00D0.D3D1.BC2D
 type 7960
 button 1:1
ephone 2
 device-security-mode none
 mac-address 0060.4724.C75A
 type 7960
 button 1:2
end

router 3

spoiler

hostname Router

ip dhcp excluded-address 10.2.0.1 10.2.0.10
ip dhcp pool COMP_DHCP
 network 10.2.0.0 255.255.255.0
 default-router 10.2.0.1
 dns-server 10.2.0.1

interface GigabitEthernet0/0
 ip address 192.168.20.2 255.255.255.0

interface GigabitEthernet0/1
 ip address 10.2.0.1 255.255.255.0

Answer 1

Most likely due to incorrect routing.
On your second router,
ip route 0.0.0.0 0.0.0.0 192.168.0.2
ip route 0.0.0.0 0.0.0.0 192.168.20.2
are the default routes to the first and third rotaries. With this config, the packets will go either to the first or to the third router. When you turn off the third router then ip route 0.0.0.0 0.0.0.0 192.168.20.2 this line stops working and everything else starts working.
Solution:
1. remove the default route and prescribe static routes depending on the networks that you have.
2. remove the default route and set up dynamic routing, it will do the rest for you.
try to solve the problem yourself, if it doesn't work, write