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Check Link Hook

This example demonstrates how to process outgoing NHRP traffic in a scenario using one Tunnel with GRE encapsulation.

../../../../../_images/topology19.svg

Test Marks In NHRP Traffic

Description

In this scenario, a traffic policy was configured to log outgoing NHRP traffic, which is non-IP Layer 3 protocol. The special hook link-out can be used to process these outgoing frames.

Scenario

Step 1: Set the following configuration in DUT0 :

set interfaces ethernet eth0 address 192.168.100.10/24
set interfaces tunnel tun0 address 10.0.0.1/32
set interfaces tunnel tun0 encapsulation gre
set interfaces tunnel tun0 local-address 192.168.100.10
set interfaces tunnel tun0 nhrp
set interfaces tunnel tun0 traffic policy link-in LOG_NHRP
set interfaces tunnel tun0 traffic policy link-out LOG_NHRP
set system login user admin authentication encrypted-password '$6$GSjsCj8gHLv$/VcqU6FLi6CT2Oxn0MJQ2C2tqnRDrYKNF8HIYWJp68nvXvPdFccDsT04.WtigUONbKYrgKg8d6rEs8PjljMkH0'
set traffic policy LOG_NHRP rule 1 log prefix NHRP__
set traffic policy LOG_NHRP rule 1 selector NHRP_SEL
set traffic selector NHRP_SEL rule 1 ether-type 8193

Note

NHRP packets use ethertype 8193 (0x2001).

Step 2: Set the following configuration in DUT1 :

set interfaces ethernet eth0 address 192.168.100.20/24
set interfaces tunnel tun0 address 10.0.0.2/32
set interfaces tunnel tun0 encapsulation gre
set interfaces tunnel tun0 local-address 192.168.100.20
set interfaces tunnel tun0 nhrp holdtime 5
set interfaces tunnel tun0 nhrp nhs 10.0.0.1 nbma 192.168.100.10
set system login user admin authentication encrypted-password '$6$GSjsCj8gHLv$/VcqU6FLi6CT2Oxn0MJQ2C2tqnRDrYKNF8HIYWJp68nvXvPdFccDsT04.WtigUONbKYrgKg8d6rEs8PjljMkH0'

Step 3: Run command protocols ip show nhrp at DUT0 and check if output matches the following regular expressions:

tun0\s+dynamic\s+10\.0\.0\.2
Show output
Iface      Type     Protocol         NBMA             Claimed NBMA     Expires(s)   Flags  Identity
tun0       local    10.0.0.1         192.168.100.10   192.168.100.10   -                   -
tun0       dynamic  10.0.0.2         192.168.100.20   192.168.100.20   5            UT

Step 4: Run command system journal show | cat at DUT0 and check if output matches the following regular expressions:

\[NHRP__-1\] ACCEPT IN=tun0 OUT=\w+
\[NHRP__-1\] ACCEPT IN= OUT=tun0
Show output
Apr 17 00:25:36.000164 osdx systemd-timedated[1142036]: Changed local time to Fri 2026-04-17 00:25:36 UTC
Apr 17 00:25:36.001550 osdx OSDxCLI[1117731]: User 'admin' executed a new command: 'set date 2026-04-17 00:25:36'.
Apr 17 00:25:36.003324 osdx systemd-journald[126917]: Time jumped backwards, rotating.
Apr 17 00:25:36.307477 osdx systemd-journald[126917]: Runtime Journal (/run/log/journal/a3fecc5be5e949c7a083b0adeea4bb21) is 1.9M, max 13.8M, 11.9M free.
Apr 17 00:25:36.311360 osdx systemd-journald[126917]: Received client request to rotate journal, rotating.
Apr 17 00:25:36.311431 osdx systemd-journald[126917]: Vacuuming done, freed 0B of archived journals from /run/log/journal/a3fecc5be5e949c7a083b0adeea4bb21.
Apr 17 00:25:36.318201 osdx OSDxCLI[1117731]: User 'admin' executed a new command: 'system journal clear'.
Apr 17 00:25:36.532971 osdx OSDxCLI[1117731]: User 'admin' executed a new command: 'system coredump delete all'.
Apr 17 00:25:36.780968 osdx OSDxCLI[1117731]: User 'admin' entered the configuration menu.
Apr 17 00:25:36.863448 osdx OSDxCLI[1117731]: User 'admin' added a new cfg line: 'set interfaces ethernet eth0 address 192.168.100.10/24'.
Apr 17 00:25:36.956030 osdx OSDxCLI[1117731]: User 'admin' added a new cfg line: 'set interfaces tunnel tun0 traffic policy link-out LOG_NHRP'.
Apr 17 00:25:37.016647 osdx OSDxCLI[1117731]: User 'admin' added a new cfg line: 'set interfaces tunnel tun0 traffic policy link-in LOG_NHRP'.
Apr 17 00:25:37.109971 osdx OSDxCLI[1117731]: User 'admin' added a new cfg line: 'set interfaces tunnel tun0 address 10.0.0.1/32'.
Apr 17 00:25:37.166279 osdx OSDxCLI[1117731]: User 'admin' added a new cfg line: 'set interfaces tunnel tun0 encapsulation gre'.
Apr 17 00:25:37.271565 osdx OSDxCLI[1117731]: User 'admin' added a new cfg line: 'set interfaces tunnel tun0 local-address 192.168.100.10'.
Apr 17 00:25:37.341812 osdx OSDxCLI[1117731]: User 'admin' added a new cfg line: 'set interfaces tunnel tun0 nhrp'.
Apr 17 00:25:37.445392 osdx OSDxCLI[1117731]: User 'admin' added a new cfg line: 'set traffic policy LOG_NHRP rule 1 log prefix NHRP__'.
Apr 17 00:25:37.521862 osdx OSDxCLI[1117731]: User 'admin' added a new cfg line: 'set traffic policy LOG_NHRP rule 1 selector NHRP_SEL'.
Apr 17 00:25:37.584447 osdx OSDxCLI[1117731]: User 'admin' added a new cfg line: 'set traffic selector NHRP_SEL rule 1 ether-type 8193'.
Apr 17 00:25:37.685554 osdx OSDxCLI[1117731]: User 'admin' added a new cfg line: 'show working'.
Apr 17 00:25:37.750794 osdx ubnt-cfgd[1148023]: inactive
Apr 17 00:25:37.827674 osdx systemd[1]: Reloading frr.service - FRRouting...
Apr 17 00:25:37.846597 osdx watchfrr[1147899]: [NG1AJ-FP2TQ] Terminating on signal
Apr 17 00:25:37.947564 osdx frrinit.sh[1148053]: Stopped watchfrr.
Apr 17 00:25:37.948775 osdx frrinit.sh[1148053]: Starting watchfrr with command: '  /usr/lib/frr/watchfrr  -d  --min-restart-interval 1 --max-restart-interval 600 --timeout 600 --restart-timeout 600 zebra mgmtd nhrpd staticd'.
Apr 17 00:25:37.958446 osdx watchfrr[1148071]: [T83RR-8SM5G] watchfrr 10.4.1 starting: vty@0
Apr 17 00:25:37.958532 osdx watchfrr[1148071]: [QDG3Y-BY5TN] zebra state -> up : connect succeeded
Apr 17 00:25:37.958575 osdx watchfrr[1148071]: [QDG3Y-BY5TN] mgmtd state -> up : connect succeeded
Apr 17 00:25:37.958628 osdx watchfrr[1148071]: [ZCJ3S-SPH5S] nhrpd state -> down : initial connection attempt failed
Apr 17 00:25:37.958630 osdx watchfrr[1148071]: [QDG3Y-BY5TN] staticd state -> up : connect succeeded
Apr 17 00:25:37.958814 osdx watchfrr[1148071]: [YFT0P-5Q5YX] Forked background command [pid 1148072]: /usr/lib/frr/watchfrr.sh restart nhrpd
Apr 17 00:25:37.963752 osdx frrinit.sh[1148072]: Cannot stop nhrpd: pid file not found
Apr 17 00:25:37.964969 osdx watchfrr.sh[1148077]: Cannot stop nhrpd: pid file not found
Apr 17 00:25:37.975263 osdx zebra[913455]: [V98V0-MTWPF] client 36 says hello and bids fair to announce only nhrp routes vrf=0
Apr 17 00:25:37.984445 osdx frrinit.sh[1148082]: sh: line 1: ipsec: command not found
Apr 17 00:25:37.995204 osdx nhrpd[1148079]: [W9E3X-A5P3X] nhrpd: set-config-loaded received, marking as loaded
Apr 17 00:25:37.996088 osdx watchfrr[1148071]: [QDG3Y-BY5TN] nhrpd state -> up : connect succeeded
Apr 17 00:25:37.996095 osdx watchfrr[1148071]: [KWE5Q-QNGFC] all daemons up, doing startup-complete notify
Apr 17 00:25:37.996590 osdx frrinit.sh[1148053]: Started watchfrr.
Apr 17 00:25:38.098152 osdx systemd[1]: Reloaded frr.service - FRRouting.
Apr 17 00:25:38.127322 osdx kernel: 8021q: adding VLAN 0 to HW filter on device eth0
Apr 17 00:25:38.171284 osdx WARNING[1148176]: No supported link modes on interface eth0
Apr 17 00:25:38.172894 osdx modulelauncher[1148176]: osdx.utils.xos cmd error: /sbin/ethtool -A eth0 autoneg on
Apr 17 00:25:38.172906 osdx modulelauncher[1148176]: Command '/sbin/ethtool -A eth0 autoneg on' returned non-zero exit status 76.
Apr 17 00:25:38.174018 osdx modulelauncher[1148176]: osdx.utils.xos cmd error: /sbin/ethtool -s eth0 autoneg on advertise Pause off Asym_Pause off --
Apr 17 00:25:38.174026 osdx modulelauncher[1148176]: Command '/sbin/ethtool -s eth0 autoneg on advertise Pause off Asym_Pause off --' returned non-zero exit status 75.
Apr 17 00:25:38.196002 osdx (udev-worker)[1148204]: Network interface NamePolicy= disabled on kernel command line.
Apr 17 00:25:38.467944 osdx cfgd[1833]: [1117731]Completed change to active configuration
Apr 17 00:25:38.479645 osdx OSDxCLI[1117731]: User 'admin' committed the configuration.
Apr 17 00:25:38.502491 osdx OSDxCLI[1117731]: User 'admin' left the configuration menu.
Apr 17 00:25:40.143750 osdx OSDxCLI[1117731]: User 'admin' executed a new command: 'protocols ip show nhrp'.
Apr 17 00:25:40.999463 osdx kernel: [NHRP__-1] ACCEPT IN=tun0 OUT= MAC=45:00:00:74:95:38:40:00:40:2f:5b:b3:c0:a8:64:14:c0:a8:64:0a:00:00:20:01
Apr 17 00:25:41.003320 osdx kernel: [NHRP__-1] ACCEPT IN= OUT=tun0 MAC=45:01:00:00:00:00:40:00:40:2f:00:00:c0:a8:64:0a:c0:a8:64:14:00:00:20:01
Apr 17 00:25:41.003362 osdx kernel: [NHRP__-1] ACCEPT IN=tun0 OUT=eth0 MAC=00:01:08:00:00:00:00:00:00:40:00:70:2b:43:00:34:01:04:04:00:04:04:00:02
Apr 17 00:25:41.999964 osdx kernel: [NHRP__-1] ACCEPT IN=tun0 OUT= MAC=45:00:00:74:96:28:40:00:40:2f:5a:c3:c0:a8:64:14:c0:a8:64:0a:00:00:20:01
Apr 17 00:25:42.000032 osdx kernel: [NHRP__-1] ACCEPT IN= OUT=tun0 MAC=45:01:00:00:00:00:40:00:40:2f:00:00:c0:a8:64:0a:c0:a8:64:14:00:00:20:01
Apr 17 00:25:42.000041 osdx kernel: [NHRP__-1] ACCEPT IN=tun0 OUT=eth0 MAC=00:01:08:00:00:00:00:00:00:40:00:70:2b:42:00:34:01:04:04:00:04:04:00:02
Apr 17 00:25:42.222869 osdx OSDxCLI[1117731]: User 'admin' executed a new command: 'protocols ip show nhrp'.

Step 5: Run command traffic policy show at DUT0 and check if output matches the following regular expressions:

1\s+NHRP_SEL\s+\b[^0]\d*
Show output
Policy LOG_NHRP -- ifc tun0 -- hook link-in prio very-high

---------------------------------------------------------------
rule   selector  pkts match  pkts eval  bytes match  bytes eval
---------------------------------------------------------------
1      NHRP_SEL           4          4          456         456
---------------------------------------------------------------
Total                     4          4          456         456

Policy LOG_NHRP -- ifc tun0 -- hook link-out prio very-high

---------------------------------------------------------------
rule   selector  pkts match  pkts eval  bytes match  bytes eval
---------------------------------------------------------------
1      NHRP_SEL           2          2          272         272
---------------------------------------------------------------
Total                     2          2          272         272
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