cray-dhcp-kea services
(ncn-mw#) Some of the commands in these procedures require an API token to be acquired and stored in the TOKEN environment variable.
export TOKEN=$(curl -s -k -S -d grant_type=client_credentials -d client_id=admin-client \
-d client_secret=`kubectl get secrets admin-client-auth -o jsonpath='{.data.client-secret}' | base64 -d` \
https://api-gw-service-nmn.local/keycloak/realms/shasta/protocol/openid-connect/token | jq -r '.access_token')
cray-dhcp-kea servicesCheck if the Kea DHCP services are running properly.
cray-dhcp-kea pods(ncn-mw#) List the cray-dhcp-kea pods.
kubectl get pods -n services -o wide | grep kea
Expected output looks similar to the following:
cray-dhcp-kea-7d4c5c9fb5-hs5gg 3/3 Running 0 33m 10.33.0.22 ncn-w011 <none> <none>
cray-dhcp-kea-7d4c5c9fb5-qtwtn 3/3 Running 0 33m 10.39.0.47 ncn-w006 <none> <none>
cray-dhcp-kea-7d4c5c9fb5-t4mkw 3/3 Running 0 24h 10.40.0.13 ncn-w005 <none> <none>
cray-dhcp-kea-helper-28256892-bl64f 0/2 Completed 0 29m 10.39.0.48 ncn-w006 <none> <none>
cray-dhcp-kea-helper-28256895-6t674 0/2 Completed 0 26m 10.39.0.53 ncn-w006 <none> <none>
cray-dhcp-kea-helper-28256898-8xzl2 0/2 Completed 0 23m 10.39.0.32 ncn-w006 <none> <none>
cray-dhcp-kea-helper-28256901-4wzql 0/2 Completed 0 20m 10.39.0.41 ncn-w006 <none> <none>
cray-dhcp-kea-helper-28256904-9h7hw 0/2 Completed 0 17m 10.39.0.48 ncn-w006 <none> <none>
cray-dhcp-kea-helper-28256907-zstfk 0/2 Completed 0 14m 10.39.0.44 ncn-w006 <none> <none>
cray-dhcp-kea-helper-28256910-566dd 0/2 Completed 0 11m 10.39.0.53 ncn-w006 <none> <none>
cray-dhcp-kea-helper-28256913-n2q2x 0/2 Completed 0 8m19s 10.39.0.48 ncn-w006 <none> <none>
cray-dhcp-kea-helper-28256916-j5w2n 0/2 Completed 0 5m19s 10.39.0.32 ncn-w006 <none> <none>
cray-dhcp-kea-helper-28256919-xnhnw 0/2 Completed 0 2m19s 10.39.0.32 ncn-w006 <none> <none>
cray-dhcp-kea-init-24-nbhng 0/2 Completed 0 8d 10.32.0.52 ncn-w001 <none> <none>
cray-dhcp-kea-postgres-0 3/3 Running 0 24h 10.39.0.28 ncn-w006 <none> <none>
cray-dhcp-kea-postgres-1 3/3 Running 0 24h 10.34.128.12 ncn-w004 <none> <none>
cray-dhcp-kea-postgres-2 3/3 Running 0 24h 10.32.0.39 ncn-w001 <none> <none>
Verify that all pods listed are in Running state.
If a cray-dhcp-kea pod is not in Running state, then perform Kubernetes troubleshooting.
This output will also show which worker nodes the cray-kea-dhcp pods are currently on. This information may be useful when debugging a Kubernetes problem.
cray-dhcp-kea service endpoints(ncn-mw#) List the cray-dhcp-kea service endpoints.
kubectl get services -n services | grep kea
Expected output looks similar to the following:
cray-dhcp-kea-api ClusterIP 10.26.142.204 <none> 8000/TCP 5d23h
cray-dhcp-kea-postgres ClusterIP 10.19.97.142 <none> 5432/TCP 5d23h
cray-dhcp-kea-postgres-0 ClusterIP 10.30.214.27 <none> 5432/TCP 5d23h
cray-dhcp-kea-postgres-1 ClusterIP 10.27.232.156 <none> 5432/TCP 5d23h
cray-dhcp-kea-postgres-2 ClusterIP 10.22.242.251 <none> 5432/TCP 5d23h
cray-dhcp-kea-postgres-config ClusterIP None <none> <none> 5d23h
cray-dhcp-kea-postgres-repl ClusterIP 10.17.107.16 <none> 5432/TCP 5d23
cray-dhcp-kea-tcp-hmn LoadBalancer 10.24.79.120 10.94.100.222 67:32120/TCP 5d23h
cray-dhcp-kea-tcp-nmn LoadBalancer 10.19.139.179 10.92.100.222 67:31652/TCP 5d23h
cray-dhcp-kea-udp-hmn LoadBalancer 10.25.203.31 10.94.100.222 67:30840/UDP 5d23h
cray-dhcp-kea-udp-nmn LoadBalancer 10.19.187.168 10.92.100.222 67:31904/UDP 5d23h
Verify that all cray-dhcp-kea services are listed as Pending.
If any cray-dhcp-kea service is showing Pending, then perform Kubernetes troubleshooting.
cray-dhcp-kea configuration is validCheck to make sure that cray-dhcp-kea is running with a valid configuration by initiating a warm configuration-reload on cray-dhcp-kea.
(ncn-mw#) Initiate the configuration reload.
curl -s -k -H "Authorization: Bearer ${TOKEN}" -X POST -H "Content-Type: application/json" -d '{ "command": "config-reload", "service": [ "dhcp4" ] }' https://api_gw_service.local/apis/dhcp-kea | jq
The expected output is:
[
{
"result": 0,
"text": "Configuration successful."
}
]
If the output is different from what is expected, then there is a configuration data issue.
cray-dhcp-kea running configurationVerify that the configuration being used is not the base configuration.
(ncn-mw#) View the current configuration.
curl -s -k -H "Authorization: Bearer ${TOKEN}" -X POST -H "Content-Type: application/json" -d '{ "command": "config-get", "service": [ "dhcp4" ] }' https://api-gw-service-nmn.local/apis/dhcp-kea | jq
Determine whether the base configuration is in use.
The base configuration will contain no system-specific data (such as MAC addresses, IP addresses, or subnets), similar to the following example:
{
"Dhcp4": {
"decline-probation-period": 3,
"sanity-checks": {
"lease-checks": "fix-del"
},
"expired-leases-processing": {
"reclaim-timer-wait-time": 6000,
"hold-reclaimed-time": 86400,
"flush-reclaimed-timer-wait-time": 100
},
"control-socket": {
"socket-name": "/cray-dhcp-kea-socket/cray-dhcp-kea.socket",
"socket-type": "unix"
},
"hooks-libraries": [
{
"library": "/usr/local/lib/kea/hooks/libdhcp_lease_cmds.so"
},
{
"library": "/usr/local/lib/kea/hooks/libdhcp_stat_cmds.so"
}
],
"interfaces-config": {
"dhcp-socket-type": "udp",
"interfaces": [
"eth0"
]
},
"lease-database": {},
"host-reservation-identifiers": [
"hw-address"
],
"reservation-mode": "global",
"reservations": [],
"subnet4": [],
"valid-lifetime": 3600,
"match-client-id": false,
"loggers": [
{
"name": "cray-dchp-kea-dhcp4",
"output_options": [
{
"output": "stdout"
}
],
"severity": "WARN"
}
]
}
}
If cray-dhcp-kea is using the base configuration, then this indicates issues generating the configuration data from cray-smd, cray-sls, and cray-bss.
Verify that those services are healthy.
cray-dhcp-kea has active DHCP leasesVerify that cray-dhcp-kea is managing DHCP leases.
(ncn-mw#) Check how many DHCP leases are found.
curl -s -k -H "Authorization: Bearer ${TOKEN}" -X POST -H "Content-Type: application/json" \
-d '{ "command": "lease4-get-all", "service": [ "dhcp4" ] }' https://api-gw-service-nmn.local/apis/dhcp-kea | jq .[].text
Expected output will be similar to:
"118 IPv4 lease(s) found."
If things are working normally, then the expectation is to have more than 0 leases found. If no leases are found, then that indicates the base configuration is being loaded or there is a network issue.
cray-dhcp-kea-helper job(ncn-mw#) Check the status of the most recent cray-dhcp-kea-helper job.
kubectl get pods -n services | grep cray-dhcp-kea-helper
Example output:
cray-dhcp-kea-helper-28256892-bl64f 0/2 Completed 0 29m
cray-dhcp-kea-helper-28256895-6t674 0/2 Completed 0 26m
cray-dhcp-kea-helper-28256898-8xzl2 0/2 Completed 0 23m
cray-dhcp-kea-helper-28256901-4wzql 0/2 Completed 0 20m
cray-dhcp-kea-helper-28256904-9h7hw 0/2 Completed 0 17m
cray-dhcp-kea-helper-28256907-zstfk 0/2 Completed 0 14m
cray-dhcp-kea-helper-28256910-566dd 0/2 Completed 0 11m
cray-dhcp-kea-helper-28256913-n2q2x 0/2 Completed 0 8m19s
cray-dhcp-kea-helper-28256916-j5w2n 0/2 Completed 0 5m19s
cray-dhcp-kea-helper-28256919-xnhnw 0/2 Completed 0 2m19s
(ncn-mw#) If the status of the most recent cray-dhcp-kea-helper job is Error, check the logs for a
description of any problems found.
kubectl logs -n services $(kubectl get pods -A|grep kea-helper| awk '{ print $2 }' | tail -n 1)
cray-dhcp-kea logs(ncn-mw#) View the pod logs.
kubectl logs -n services -l app.kubernetes.io/instance=cray-dhcp-kea -c cray-dhcp-kea
Beginning of example output:
2020-08-03 21:47:50.580 INFO [kea-dhcp4.dhcpsrv/10] DHCPSRV_MEMFILE_LEASE_FILE_LOAD loading leases from file /cray-dhcp-kea-socket/dhcp4.leases
2020-08-03 21:47:50.580 INFO [kea-dhcp4.dhcpsrv/10] DHCPSRV_MEMFILE_LFC_SETUP setting up the Lease File Cleanup interval to 3600 sec
2020-08-03 21:47:50.580 WARN [kea-dhcp4.dhcpsrv/10] DHCPSRV_OPEN_SOCKET_FAIL failed to open socket: the interface eth0 has no usable IPv4 addresses configured
2020-08-03 21:47:50.580 WARN [kea-dhcp4.dhcpsrv/10] DHCPSRV_NO_SOCKETS_OPEN no interface configured to listen to DHCP traffic
2020-08-03 21:48:00.602 INFO [kea-dhcp4.commands/10] COMMAND_RECEIVED Received command 'lease4-get-all'
{"Dhcp4": {"control-socket": {"socket-name": "/cray-dhcp-kea-socket/cray-dhcp-kea.socket", "socket-type": "unix"}, "hooks-libraries": [{"library": "/usr/local/lib/kea/hooks/libdhcp_lease_cmds.so"},
Tail end of example output:
waiting 10 seconds for any leases to be given out...
[{'arguments': {'leases': []}, 'result': 3, 'text': '0 IPv4 lease(s) found.'}]
2020-08-03 21:48:22.734 INFO [kea-dhcp4.commands/10] COMMAND_RECEIVED Received command 'config-get'
(ncn-mw#) Display only potential error messages in the pod logs.
kubectl logs -n services -l app.kubernetes.io/instance=cray-dhcp-kea -c cray-dhcp-kea | grep -i error
Use the Kea API to retrieve data from the DHCP lease database.
(ncn-mw#) Run desired commands to check DHCP leases.
Get all leases.
Warning: this may cause the terminal to crash, if there is too much output.
curl -s -k -H "Authorization: Bearer ${TOKEN}" -X POST -H "Content-Type: application/json" \
-d '{ "command": "lease4-get-all", "service": [ "dhcp4" ] }' https://api-gw-service-nmn.local/apis/dhcp-kea | jq
Determine the hostname or MAC address from an IP address.
IP=<IP_address>
curl -s -k -H "Authorization: Bearer ${TOKEN}" -X POST -H "Content-Type: application/json" \
-d "{ \"command\": \"lease4-get\", \"service\": [ \"dhcp4\" ], \"arguments\": { \"ip-address\": \"${IP}\" } }" \
https://api-gw-service-nmn.local/apis/dhcp-kea | jq
Determine the hostname or IP address from the MAC address
MAC=<MAC_address>
curl -H "Authorization: Bearer ${TOKEN}" -X POST -H "Content-Type: application/json" \
-d '{ "command": "lease4-get-all", "service": [ "dhcp4" ] }' https://api-gw-service-nmn.local/apis/dhcp-kea | \
jq ".[].arguments.leases[] | select(.\"hw-address\"==\"${MAC}\")"
Determine MAC or IP address from the hostname.
The hostname can be either the component name (xname) or an alias, depending on the type of hardware.
HNAME=<hostname>
curl -H "Authorization: Bearer ${TOKEN}" -X POST -H "Content-Type: application/json" \
-d '{ "command": "lease4-get-all", "service": [ "dhcp4" ] }' https://api-gw-service-nmn.local/apis/dhcp-kea | \
jq ".[].arguments.leases[] | select(.\"hostname\"==\"${HNAME}\")"
Hardware State Manager (HSM) has two important parts:
networks.yaml and other sources).(ncn-mw#) Retrieve SLS data.
curl -s -k -H "Authorization: Bearer ${TOKEN}" https://api-gw-service-nmn.local/apis/sls/v2/hardware | jq | less
The output from SLS should look similar to the following:
{
"Parent": "x1000c7s1b0",
"Xname": "x1000c7s1b0n0",
"Type": "comptype_node",
"Class": "Mountain",
"TypeString": "Node",
"ExtraProperties": {
"Aliases": [
"nid001228"
],
"NID": 1228,
"Role": "Compute"
}
}
(ncn-mw#) Query SMD.
There are a number of options.
List all interfaces
curl -s -k -H "Authorization: Bearer ${TOKEN}" https://api-gw-service-nmn.local/apis/smd/hsm/v2/Inventory/EthernetInterfaces | jq
Lookup by MAC address
The MAC address should contain no colons.
MAC=<MAC address>
curl -s -k -H "Authorization: Bearer ${TOKEN}" https://api-gw-service-nmn.local/apis/smd/hsm/v2/Inventory/EthernetInterfaces/${MAC} | jq
Lookup by xname
XNAME=<xname>
curl -s -k -H "Authorization: Bearer ${TOKEN}" https://api-gw-service-nmn.local/apis/smd/hsm/v2/Inventory/EthernetInterfaces?ComponentID=${XNAME} | jq
Lookup by IP address
IP=<IP address>
curl -s -k -H "Authorization: Bearer ${TOKEN}" https://api-gw-service-nmn.local/apis/smd/hsm/v2/Inventory/EthernetInterfaces?IPAddress=${IP} | jq
Output from SMD should look similar to the following:
{
"ID": "0040a6838b0e",
"Description": "",
"MACAddress": "0040a6838b0e",
"IPAddresses": [{"IPAddress":"10.100.1.147"}],
"LastUpdate": "2020-07-24T23:44:24.578476Z",
"ComponentID": "x1000c7s1b0n0",
"Type": "Node"
}
A sign of a duplicate IP address is seeing a DECLINE message from the client to the server.
10.40.0.0.337 > 10.42.0.58.67: BOOTP/DHCP, Request from b4:2e:99:be:1a:d3, length 301, hops 1, xid 0x9d1210d, Flags [none]
Gateway-IP 10.252.0.2
Client-Ethernet-Address b4:2e:99:be:1a:d3
Vendor-rfc1048 Extensions
Magic Cookie 0x63825363
DHCP-Message Option 53, length 1: Decline
Client-ID Option 61, length 19: hardware-type 255, 99:be:1a:d3:00:01:00:01:26:c8:55:c3:b4:2e:99:be:1a:d3
Server-ID Option 54, length 4: 10.42.0.58
Requested-IP Option 50, length 4: 10.252.0.26
Agent-Information Option 82, length 22:
Circuit-ID SubOption 1, length 20: vlan2-ethernet1/1/12
To test for duplicate IP addresses, ping the suspected IP address while turning off the node. If ping continues to get responses after the node is down, then there is a duplicate IP address.
The symptom of this looks similar to the following on a node console during boot:
IPv6: ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready
dracut-initqueue[1902]: wicked: eth0: Request to acquire DHCPv4 lease with UUID 13b0675f-12cb-0a00-2f0a-000001000000
dracut-initqueue[1902]: wicked: eth0: Declining DHCPv4 lease with address 10.252.0.51
random: fast init done
dracut-initqueue[1902]: wicked: eth0: Declining DHCPv4 lease with address 10.252.0.53
dracut-initqueue[1902]: wicked: eth0: Declining DHCPv4 lease with address 10.252.0.54
dracut-initqueue[1902]: wicked: eth0: Declining DHCPv4 lease with address 10.252.0.55
random: crng init done
random: 7 urandom warning(s) missed due to ratelimiting
dracut-initqueue[1902]: wicked: eth0: Declining DHCPv4 lease with address 10.252.0.56
dracut-initqueue[1902]: wicked: eth0: Declining DHCPv4 lease with address 10.252.0.57
dracut-initqueue[1902]: wicked: eth0: Declining DHCPv4 lease with address 10.252.0.58
dracut-initqueue[1902]: wicked: eth0: Declining DHCPv4 lease with address 10.252.0.59
dracut-initqueue[1902]: wicked: eth0: Declining DHCPv4 lease with address 10.252.0.60
dracut-initqueue[1902]: wicked: eth0: Declining DHCPv4 lease with address 10.252.0.51
dracut-initqueue[1902]: wicked: eth0: Declining DHCPv4 lease with address 10.252.0.53
dracut-initqueue[1902]: wicked: eth0: Declining DHCPv4 lease with address 10.252.0.54
dracut-initqueue[1902]: wicked: eth0: Declining DHCPv4 lease with address 10.252.0.61
dracut-initqueue[1902]: wicked: eth0: Declining DHCPv4 lease with address 10.252.0.62
dracut-initqueue[1902]: wicked: eth0: Declining DHCPv4 lease with address 10.252.0.63
dracut-initqueue[1902]: wicked: eth0: Declining DHCPv4 lease with address 10.252.0.64
dracut-initqueue[1902]: wicked: eth0: Declining DHCPv4 lease with address 10.252.0.65
dracut-initqueue[1902]: wicked: eth0: Declining DHCPv4 lease with address 10.252.0.66
dracut-initqueue[1902]: wicked: eth0: Declining DHCPv4 lease with address 10.252.0.67
This indicates that an IP address being allocated is already being used. If that is the case, use the following procedure to troubleshoot and remediate the problem.
(ncn-mw#) Determine the IP address that is supposed to be set for node.
Example commands:
Check by MAC address (no colons).
curl -f -s -k -H "Authorization: Bearer ${TOKEN}" https://api_gw_service.local/apis/smd/hsm/v2/Inventory/EthernetInterfaces/18c04d13d73c
Check by xname.
curl -f -s -k -H "Authorization: Bearer ${TOKEN}" https://api_gw_service.local/apis/smd/hsm/v2/Inventory/EthernetInterfaces?ComponentID=x3000c0s25b0n0
Output should look similar to the following:
{
"ID": "18c04d13d73c",
"Description": "Ethernet Interface Lan1",
"MACAddress": "18:c0:4d:13:d7:3c",
"IPAddresses": [{,"IPAddress":"10.252.0.78"}],
"LastUpdate": "2020-09-20T19:46:04.811779Z",
"ComponentID": "x3000c0s25b0n0",
"Type": "Node"
}
(ncn-mw#) Ping the IP address from the SMD entry to see if something is responding to it.
Example command:
ping -c 3 10.252.0.78
Example output:
PING 10.252.0.78 (10.252.0.78) 56(84) bytes of data.
64 bytes from 10.252.0.78: icmp_seq=1 ttl=64 time=0.102 ms
64 bytes from 10.252.0.78: icmp_seq=2 ttl=64 time=0.229 ms
64 bytes from 10.252.0.78: icmp_seq=3 ttl=64 time=0.096 ms
--- 10.252.0.78 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2054ms
rtt min/avg/max/mdev = 0.096/0.142/0.229/0.062 ms
If ping receives responses, then that confirms that a device is responding to the IP address. In that case, the DHCP reservation for the device must be moved to another IP address.
(ncn-mw#) Remove the entry by its MAC address (without colons) in the SMD Ethernet table.
Example:
curl -f -X DELETE -s -k -H "Authorization: Bearer ${TOKEN}" https://api_gw_service.local/apis/smd/hsm/v1/Inventory/EthernetInterfaces/18c04d13d73c
Wait five minutes for HMS discovery to recreate the SMD Ethernet table entry.
Reboot the node and let the node get an IP address from DHCP.
The standard discovery/DHCP/DNS process should complete in about 5 minutes. This will get the node to boot up until DVS is needed (if the node is using DVS).
If the node is using DVS, follow the DVS node map update procedure.
See Troubleshoot Node Map IP Change Issues in the Cray Shasta DVS Administration Guide.
Verify that the Metal Load Balancer (MetalLB) is peering to the spine switches via the Border Gateway Protocol (BGP). The commands in these sections must be run on the spine switches themselves.
(sw#) Show the BGP status.
show ip bgp summary
All the neighbors should be in the ESTABLISHED state, as seen in the following example output:
VRF name : default
BGP router identifier : 10.252.0.1
local AS number : 65533
BGP table version : 6
Main routing table version: 6
IPV4 Prefixes : 84
IPV6 Prefixes : 0
L2VPN EVPN Prefixes : 0
------------------------------------------------------------------------------------------------------------------
Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
------------------------------------------------------------------------------------------------------------------
10.252.0.4 4 65533 465 501 6 0 0 0:03:37:43 ESTABLISHED/28
10.252.0.5 4 65533 463 501 6 0 0 0:03:36:51 ESTABLISHED/28
10.252.0.6 4 65533 463 500 6 0 0 0:03:36:39 ESTABLISHED/28
(sw#) If the State/PfxRcd is IDLE, then restart the BGP process.
clear ip bgp all
(sw#) Verify that routes to Kea via all workers are available.
Routes to Kea (10.92.100.222) via all workers (in the above examples, 10.252.0.4 - 10.252.0.6) should be available.
show ip route 10.92.100.222
Example output:
Routes:All worker nodes (in the above example 3) should be peered with the spine BGP.
Example:
sw-spine01 [standalone: master] # show ip route 10.92.100.222
Flags:
F: Failed to install in H/W
B: BFD protected (static route)
i: BFD session initializing (static route)
x: protecting BFD session failed (static route)
c: consistent hashing
p: partial programming in H/W
VRF Name default:
------------------------------------------------------------------------------------------------------
Destination Mask Flag Gateway Interface Source AD/M
------------------------------------------------------------------------------------------------------
default 0.0.0.0 c 10.102.255.9 eth1/16 static 1/1
10.92.100.222 255.255.255.255 c 10.252.0.4 vlan2 bgp 200/0
c 10.252.0.5 vlan2 bgp 200/0
c 10.252.0.6 vlan2 bgp 200/0
(sw#) Show BGP status.
show bgp ipv4 u s
Example output:
VRF : default
BGP Summary
-----------
Local AS : 65533 BGP Router Identifier : 10.252.0.3
Peers : 4 Log Neighbor Changes : No
Cfg. Hold Time : 180 Cfg. Keep Alive : 60
Confederation Id : 0
Neighbor Remote-AS MsgRcvd MsgSent Up/Down Time State AdminStatus
10.252.0.2 65533 45052 45044 02m:02w:02d Established Up
10.252.1.7 65533 78389 90090 02m:02w:02d Established Up
10.252.1.8 65533 78384 90059 02m:02w:02d Established Up
10.252.1.9 65533 78389 90108 02m:02w:02d Established Up
tcpdumpIf a host is not getting an IP address, then run a packet capture to see if DHCP traffic is being transmitted.
tcpdump -w dhcp.pcap -envli bond0.nmn0 port 67 or port 68
This will make a .pcap file named DHCP in the current directory. It will collect all DHCP traffic on the specified port. In this example, it is looking for DHCP traffic on
the NMN interface (10.252.0.0/17).
View the DHCP traffic:
tcpdump -r dhcp.pcap -v -n
The output may be very long, which can be handled by using filters.
Do a tcpdump for a certain MAC address:
tcpdump -i eth0 -vvv -s 1500 '((port 67 or port 68) and (udp[38:4] = 0x993b7030))'
This example is using the MAC address of b4:2e:99:3b:70:30. It will show the output on the terminal and not save to a file.
It is also possible to run tcpdump from the Dell Leaf/CDU switches.
(sw#) Example of tcpdump for DHCP traffic on the NMN:
system "sudo tcpdump -enli br2 port 67 or port 68"
(sw#) Example of tcpdump for DHCP traffic for interface 1/1/4:
system "sudo tcpdump -enli e101-004-0 port 67 or port 68"