ACL_Refresher_R1toR5

I have done a “wr er” / “reload” on R1 and R5, configuring only loopbacks, and opened Fa0/1 interfaces to be Area 0 between the two. No NBMA, no oddities (hopefully), and see how it works with a lot of troubleshooting.

So to begin, I’ll set R1 first as the NTP master with a clock time:

R1#clock set 18:00:00 30 mar 2017
R1#
*Mar 30 18:00:00.000: %SYS-6-CLOCKUPDATE: System clock has been updated from 18:43:02 UTC Thu Mar 30 2017 to 18:00:00 UTC Thu Mar 30 2017, configured from console by console.
R1#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
R1(config)#ntp master ?
  <1-15>  Stratum number
  <cr>

R1(config)#ntp master 3
R1(config)#int fa0/1
R1(config-if)#ntp broadcast ?
  client       Listen to NTP broadcasts
  destination  Configure broadcast destination address
  key          Configure broadcast authentication key
  version      Configure NTP version
  <cr>

R1(config-if)#ntp broadcast
R1(config-if)#

So that is all configured, unfortunately R1 is running on 12.x IOS code, so it is using NTPv3 (and is only capable of running version 3). So lets go to R5 and see if we can get this working:

R5#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
R5(config)#int fa0/1
R5(config-if)#ntp ?
  broadcast  Configure NTP broadcast service
  disable    Disable NTP traffic (both IP and IPv6)
  multicast  Configure NTP multicast service

R5(config-if)#ntp broadcast ?
  client       Listen to NTP broadcasts
  destination  Configure broadcast destination address
  key          Configure broadcast authentication key
  version      Configure NTP version
  <cr>

R5(config-if)#ntp broadcast client ?
  <cr>

R5(config-if)#ntp broadcast client
R5(config-if)#^Z
R5#debug
*Mar 30 17:05:01.491: %SYS-5-CONFIG_I: Configured from console by console
R5#debug ntp pack
NTP packets debugging is on
R5#
*Mar 30 17:05:10.659: NTP message received from 172.12.15.1 on interface ‘FastEthernet0/1’ (255.255.255.255).
R5#sh clock
*17:05:27.923 UTC Thu Mar 30 2017
R5#

Just as easy as that, that is how it is supposed to work 🙂

One thing I noticed on R5 running 15.1 IOS code is the NTP messages are so much smaller and concise, a lot of the basic infrastructure works the same between IOS versions but I do like some of the subtle differences.

So now I’ll reverse roles with debug still running, and see what happens starting with R5:

R5#sh clock
.18:45:28.132 UTC Thu Mar 30 2017
R5#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
R5(config)#ntp master ?
  <1-15>  Stratum number
  <cr>

R5(config)#ntp master 3 ?
  <cr>

R5(config)#ntp master 3
R5(config)#int fa0/1
R5(config-if)#ntp broadcast ?
  client       Listen to NTP broadcasts
  destination  Configure broadcast destination address
  key          Configure broadcast authentication key
  version      Configure NTP version
  <cr>

R5(config-if)#ntp broadcast version ?
  <2-4>  NTP version number

R5(config-if)#ntp broadcast version 4
R5(config-if)#^Z
R5#deb
.Mar 30 18:49:32.833: %SYS-5-CONFIG_I: Configured from console by console
R5#debug ntp pack
.Mar 30 18:49:38.737: NTP message sent to 255.255.255.255, from interface ‘FastEthernet0/1’ (172.12.15.5).
R5#debug ntp pack
NTP packets debugging is on
R5#

I changed it to Version 4 NTP to see if R1 who only understands up to version 3 can still pick up the time from R5, so debugs running lets see what happens with R1:

R1#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
R1(config)#int fa0/1
R1(config-if)#ntp broadcast client
R1(config-if)#do sh clock
18:54:12.613 UTC Thu Mar 30 2017
R1(config-if)#
ASR#2
[Resuming connection 2 to r5 … ]

Mar 30 18:52:48.736: NTP message sent to 255.255.255.255, from interface ‘FastEthernet0/1’ (172.12.15.5).
R5#
Mar 30 18:53:54.736: NTP message sent to 255.255.255.255, from interface ‘FastEthernet0/1’ (172.12.15.5).
R5#
Mar 30 18:54:57.735: NTP message sent to 255.255.255.255, from interface ‘FastEthernet0/1’ (172.12.15.5).
R5#sh clock
18:55:04.327 UTC Thu Mar 30 2017
R5#clock set 21:00:00 30 mar 2017
R5#
.Mar 30 21:00:00.000: %SYS-6-CLOCKUPDATE: System clock has been updated from 18:55:35 UTC Thu Mar 30 2017 to 21:00:00 UTC Thu Mar 30 2017, configured from console by console.
R5#
.Mar 30 21:00:26.763: NTP message sent to 255.255.255.255, from interface ‘FastEthernet0/1’ (172.12.15.5).
R5#
ASR#1
[Resuming connection 1 to r1 … ]

R1(config-if)#do sh clock
18:56:17.338 UTC Thu Mar 30 2017
R1(config-if)#

So it is not updating, as I believe it just doesn’t understand NTP version 4, so I’ll change it to version 3 and see if we can get this working:

R5(config)#int fa0/1
R5(config-if)#no ntp broadcast version 4
R5(config-if)#ntp broadcast version 3
R5(config-if)#do sh clock
21:03:18.143 UTC Thu Mar 30 2017
R5(config-if)#
Mar 30 21:03:55.763: NTP message sent to 255.255.255.255, from interface ‘FastEthernet0/1’ (172.12.15.5).
R5(config-if)#
ASR#1
[Resuming connection 1 to r1 … ]

R1(config-if)#do sh clock
18:59:56.341 UTC Thu Mar 30 2017

So it’s not liking that, so I tried removing and re-adding the the “ntp broadcast client” on R1 to see if that’d kick it into gear but it did not so I did have to reboot R1, however:

R1>en
Password:
R1#sh clock
21:24:00.844 UTC Thu Mar 30 2017
R1#

Almost gets me teary how proud I am of my routers to work as expected 🙂

So that is it, done with NTP for now, we have officially beaten that dead horse into the ground!

One thing to note, as this NTP battle has underscored running IOS code 12.x sucks for the current CCNP ROUTE exam, all of the concepts we have troubleshot have been overcome by logic, and not incompatibility between the versions. I will definitely demonstrate on my 2 routers I have running IOS 15.x any critical to know material that are not on my NBMA routers (R1 / R2 / R3 are on 12.x IOS code), however it really does not alter the behaviors of most protocols beyond newer versions of them – So don’t take this as irrelevant due to the 12.x code over the NBMA I would just rather invest that money into the exams