Network time protocol provides pretty much what its name says time. provide correct time to all network devices. in other words, NTP synchronizes the clock of the computer system over packet switch, variable-latency data networks. Correct network time within the network is important.
Correct time allows the tracking of the event in the network in the correct order. Cock synchronize is critical for the correct interpretation of events within the Syslog data.
Advantages of NTP :
It provides internet synchronization between the computer devices.
NTP provides enhanced security within the premises.
NTP is used in authentication systems.
NTP provides network acceleration which helps in troubleshooting problems.
let's see the configuration on the router:
Topology:
Goal :
- configure the topology as per the diagram above.
- configure the IP addresses to their ports
- configure routing with EIGRP AS 65100 and advertise all the ports
- configure NTP on router 3, server address will loopback 0
- make sure the rest of the routers get time which is provided by our NTP server.
R1(config)#interface fastEthernet 0/0
R1(config-if)#ip address 10.1.1.1 255.0.0.0
R1(config-if)#no shutdown
R1(config-if)#no keepalive
R1(config-if)#exit
R1(config)#interface serial 4/0
R1(config-if)#ip address 1.1.1.1 255.0.0.0
R1(config-if)#no shutdown
R1(config-if)#exit
R1(config)#interface loopback 0
R1(config-if)#ip address 192.168.1.1 255.255.255.0
R1(config-if)#no shutdown
R1(config-if)#exit
R1(config)#do show ip int br
Interface IP-Address OK? Method Status Protocol
FastEthernet0/0 10.1.1.1 YES manual up up
Serial4/0 1.1.1.1 YES manual up up
Loopback0 192.168.1.1 YES manual up up
R2(config)#interface fastEthernet 0/0
R2(config-if)#ip address 20.1.1.1 255.0.0.0
R2(config-if)#no shutdown
R2(config-if)#no keepalive
R2(config-if)#exit
R2(config)#interface serial 4/0
R2(config-if)#ip address 1.1.1.2 255.0.0.0
R2(config-if)#no shutdown
R2(config-if)#exit
R2(config)#interface serial 4/1
R2(config-if)#ip address 2.2.2.1 255.0.0.0
R2(config-if)#no shutdown
R2(config-if)#exit
R2(config)#interface loopback 0
R2(config-if)#ip address 192.168.2.2 255.255.255.0
R2(config-if)#no shutdown
R2(config-if)#exit
R2(config)#do show ip int br
Interface IP-Address OK? Method Status Protocol
FastEthernet0/0 20.1.1.1 YES manual up up
Serial4/0 1.1.1.2 YES manual up up
Serial4/1 2.2.2.1 YES manual up up
Loopback0 192.168.2.2 YES manual up up
R3(config)#interface fastEthernet 0/0
R3(config-if)#ip address 30.1.1.1 255.0.0.0
R3(config-if)#no shutdown
R3(config-if)#no keepalive
R3(config-if)#exit
R3(config)#interface serial 4/1
R3(config-if)#ip address 2.2.2.2 255.0.0.0
R3(config-if)#no shutdown
R3(config-if)#exit
R3(config)#interface serial 4/2
R3(config-if)#ip address 3.3.3.2 255.0.0.0
R3(config-if)#no shutdown
R3(config-if)#exit
R3(config)#interface loopback 0
R3(config-if)#ip address 192.168.3.3 255.255.255.0
R3(config-if)#no shutdown
R3(config-if)#exit
R3(config)#do show ip int br
Interface IP-Address OK? Method Status Protocol
FastEthernet0/0 30.1.1.1 YES manual up up
Serial4/1 2.2.2.2 YES manual up up
Serial4/2 3.3.3.2 YES manual up up
Loopback0 192.168.3.3 YES manual up up
R4(config)#interface fas
R4(config)#interface fastEthernet 0/0
R4(config-if)#ip address 40.1.1.1 255.0.0.0
R4(config-if)#no shutdown
R4(config-if)#no keepalive
R4(config-if)#exit
R4(config)#interface serial 4/2
R4(config-if)#ip address 3.3.3.3 255.0.0.0
R4(config-if)#no shutdown
R4(config-if)#exit
R4(config)#interface loopback 0
R4(config-if)#ip address 192.168.4.4 255.255.255.0
R4(config-if)#exit
R4(config)#do show ip int br
Interface IP-Address OK? Method Status Protocol
FastEthernet0/0 40.1.1.1 YES manual up up
Serial4/2 3.3.3.3 YES manual up up
Loopback0 192.168.4.4 YES manual up up
R1(config)#router eigrp 65100
R1(config-router)#network 10.0.0.0
R1(config-router)#network 1.0.0.0
R1(config-router)#network 192.168.1.0
R1(config-router)#no auto-summary
R1(config-router)#exit
R2(config)#router eigrp 65100
R2(config-router)#network 20.0.0.0
R2(config-router)#network 1.0.0.0
R2(config-router)#network 2.0.0.0
R2(config-router)#network 192.168.2.0
R2(config-router)#no auto-summary
R2(config-router)#exit
*Feb 11 12:54:25.263: %DUAL-5-NBRCHANGE: EIGRP-IPv4 65100: Neighbor 1.1.1.1 (Serial4/0) is up: new adjacency
R3(config)#router eigrp 65100
R3(config-router)#network 30.0.0.0
R3(config-router)#network 2.0.0.0
R3(config-router)#network 2.0.0.0
R3(config-router)#network 3.0.0.0
R3(config-router)#network 192.168.3.0
R3(config-router)#no au
R3(config-router)#no auto-summary
R3(config-router)#exit
R3(config)#end
*Feb 11 12:54:58.699: %DUAL-5-NBRCHANGE: EIGRP-IPv4 65100: Neighbor 2.2.2.1 (Serial4/1) is up: new adjacency
*Feb 11 12:55:29.027: %DUAL-5-NBRCHANGE: EIGRP-IPv4 65100: Neighbor 3.3.3.3 (Serial4/2) is up: new adjacency
R4(config)#router eigrp 65100
R4(config-router)#network 40.0.0.0
R4(config-router)#network 3.0.0.0
R4(config-router)#network 192.168.4.0
R4(config-router)#no auto-summary
R4(config-router)#exit
R4(config)#end
*Feb 11 12:55:08.211: %DUAL-5-NBRCHANGE: EIGRP-IPv4 65100: Neighbor 3.3.3.2 (Serial4/2) is up: new adjacency
R1#show eigrp protocols
EIGRP-IPv4 Protocol for AS(65100)
Metric weight K1=1, K2=0, K3=1, K4=0, K5=0
NSF-aware route hold timer is 240
Router-ID: 192.168.1.1
Topology : 0 (base)
Active Timer: 3 min
Distance: internal 90 external 170
Maximum path: 4
Maximum hopcount 100
Maximum metric variance 1
R1#show ip route eigrp
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP
+ - replicated route, % - next hop override
Gateway of last resort is not set
D 2.0.0.0/8 [90/2681856] via 1.1.1.2, 00:02:52, Serial4/0
D 3.0.0.0/8 [90/3193856] via 1.1.1.2, 00:02:00, Serial4/0
D 20.0.0.0/8 [90/2172416] via 1.1.1.2, 00:02:19, Serial4/0
D 30.0.0.0/8 [90/2684416] via 1.1.1.2, 00:02:05, Serial4/0
D 40.0.0.0/8 [90/3196416] via 1.1.1.2, 00:01:36, Serial4/0
D 192.168.2.0/24 [90/2297856] via 1.1.1.2, 00:02:47, Serial4/0
D 192.168.3.0/24 [90/2809856] via 1.1.1.2, 00:01:54, Serial4/0
D 192.168.4.0/24 [90/3321856] via 1.1.1.2, 00:01:31, Serial4/0
R2#show eigrp protocols
EIGRP-IPv4 Protocol for AS(65100)
Metric weight K1=1, K2=0, K3=1, K4=0, K5=0
NSF-aware route hold timer is 240
Router-ID: 192.168.2.2
Topology : 0 (base)
Active Timer: 3 min
Distance: internal 90 external 170
Maximum path: 4
Maximum hopcount 100
Maximum metric variance 1
R2#show ip route eigrp
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP
+ - replicated route, % - next hop override
Gateway of last resort is not set
D 3.0.0.0/8 [90/2681856] via 2.2.2.2, 00:01:48, Serial4/1
D 10.0.0.0/8 [90/2172416] via 1.1.1.1, 00:02:47, Serial4/0
D 30.0.0.0/8 [90/2172416] via 2.2.2.2, 00:01:53, Serial4/1
D 40.0.0.0/8 [90/2684416] via 2.2.2.2, 00:01:22, Serial4/1
D 192.168.1.0/24 [90/2297856] via 1.1.1.1, 00:02:47, Serial4/0
D 192.168.3.0/24 [90/2297856] via 2.2.2.2, 00:01:43, Serial4/1
D 192.168.4.0/24 [90/2809856] via 2.2.2.2, 00:01:17, Serial4/1
R3#show eigrp protocols
EIGRP-IPv4 Protocol for AS(65100)
Metric weight K1=1, K2=0, K3=1, K4=0, K5=0
NSF-aware route hold timer is 240
Router-ID: 192.168.3.3
Topology : 0 (base)
Active Timer: 3 min
Distance: internal 90 external 170
Maximum path: 4
Maximum hopcount 100
Maximum metric variance 1
R3#show ip ei
R3#show ip eigrp route
^
% Invalid input detected at '^' marker.
R3#show ip route ei
R3#show ip route eigrp
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP
+ - replicated route, % - next hop override
Gateway of last resort is not set
D 1.0.0.0/8 [90/2681856] via 2.2.2.1, 00:01:30, Serial4/1
D 10.0.0.0/8 [90/2684416] via 2.2.2.1, 00:01:30, Serial4/1
D 20.0.0.0/8 [90/2172416] via 2.2.2.1, 00:01:30, Serial4/1
D 40.0.0.0/8 [90/2172416] via 3.3.3.3, 00:01:00, Serial4/2
D 192.168.1.0/24 [90/2809856] via 2.2.2.1, 00:01:30, Serial4/1
D 192.168.2.0/24 [90/2297856] via 2.2.2.1, 00:01:30, Serial4/1
D 192.168.4.0/24 [90/2297856] via 3.3.3.3, 00:00:54, Serial4/2
R4#show eigrp protocols
EIGRP-IPv4 Protocol for AS(65100)
Metric weight K1=1, K2=0, K3=1, K4=0, K5=0
NSF-aware route hold timer is 240
Router-ID: 192.168.4.4
Topology : 0 (base)
Active Timer: 3 min
Distance: internal 90 external 170
Maximum path: 4
Maximum hopcount 100
Maximum metric variance 1
R4#show ip route ei
R4#show ip route eigrp
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP
+ - replicated route, % - next hop override
Gateway of last resort is not set
D 1.0.0.0/8 [90/3193856] via 3.3.3.2, 00:00:39, Serial4/2
D 2.0.0.0/8 [90/2681856] via 3.3.3.2, 00:00:39, Serial4/2
D 10.0.0.0/8 [90/3196416] via 3.3.3.2, 00:00:39, Serial4/2
D 20.0.0.0/8 [90/2684416] via 3.3.3.2, 00:00:39, Serial4/2
D 30.0.0.0/8 [90/2172416] via 3.3.3.2, 00:00:39, Serial4/2
D 192.168.1.0/24 [90/3321856] via 3.3.3.2, 00:00:39, Serial4/2
D 192.168.2.0/24 [90/2809856] via 3.3.3.2, 00:00:39, Serial4/2
D 192.168.3.0/24 [90/2297856] via 3.3.3.2, 00:00:39, Serial4/2
R3#show clock
*13:05:18.351 UTC Fri Feb 11 2022
R3#clock set 15:15:15 25 july 2020
*Jul 25 15:15:15.000: %SYS-6-CLOCKUPDATE: System clock has been updated from 13:06:12 UTC Fri Feb 11 2022 to 15:15:15 UTC Sat Jul 25 2020, configured from console by console.
R3#show clock
15:15:23.199 UTC Sat Jul 25 2020
R3(config)#NTP master 8
R3(config)#exit
R3(config)#ntp source loopback 0
R3(config)#ntp server 192.168.3.3
R1#show clock
*13:14:36.687 UTC Fri Feb 11 2022
R1#show clock
*13:14:39.259 UTC Fri Feb 11 2022
R1(config)#ntp server 192.168.3.3
R1(config)#exit
R1#show clock
*15:23:34.069 UTC Sat Jul 25 2020
R2#show clock
*13:13:01.619 UTC Fri Feb 11 2022
R2(config)#ntp server 192.168.3.3
R2(config)#exit
R2#show clock
*15:24:01.200 UTC Sat Jul 25 2020
R4#show clock
*13:14:40.535 UTC Fri Feb 11 2022
R4(config)#ntp server 192.168.3.3
R4(config)#exit
R4#show clock
15:24:56.677 UTC Sat Jul 25 2020
R3#show ntp packets
Ntp In packets : 27
Ntp Out packets : 36
Ntp bad version packets : 0
Ntp protocol error packets : 0
R3#show ntp status
Clock is synchronized, stratum 8, reference is 127.127.1.1
nominal freq is 250.0000 Hz, actual freq is 250.0000 Hz, precision is 2**18
ntp uptime is 55200 (1/100 of seconds), resolution is 4000
reference time is E2C6CD63.0A3E5987 (15:25:23.040 UTC Sat Jul 25 2020)
clock offset is 0.0000 msec, root delay is 0.00 msec
root dispersion is 0.35 msec, peer dispersion is 0.23 msec
loopfilter state is 'CTRL' (Normal Controlled Loop), drift is 0.000000000 s/s
system poll interval is 16, last update was 8 sec ago.
R3#show ntp associations
address ref clock st when poll reach delay offset disp
*~127.127.1.1 .LOCL. 7 14 16 377 0.000 0.000 0.235
~192.168.3.3 .INIT. 16 - 64 0 0.000 0.000 15937.
* sys.peer, # selected, + candidate, - outlyer, x falseticker, ~ configured
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