I am working with a small ISP that got a /22 of v4 space and is using
kea 1.6.2 in HA mode on two VMs. From the /22 they use a /23 for DHCP
customers. The rest is for statics, loopbacks, etc.
The servers are sitting behind a Juniper MX104 using subscriber services
so the stanard, get a dhcp packet with a particular DHCP Agent info of
double tag, start to build the demux interface, look the customer up in
Radius and assign them an IP address via DHCP and finish the demux
interface on the last DHCP ACK.
They have nearly exhausted the /23 so they would like to add another
small prefix (/26) to get them another 60 addresses or so to tied them
over until the can pick up another /22 or so to move their dhcp
customers too.
Working REDACTED config...
---
{
"Dhcp4": {
"interfaces-config": {
"interfaces": [ "eth0", "eth1", "eth2" ]
},
[...]
"valid-lifetime": 4000,
"renew-timer": 1000,
"rebind-timer": 2000,
"reservation-mode": "disabled",
"control-socket": {
"socket-type": "unix",
"socket-name": "/tmp/kea-dhcp4-ctrl.sock"
},
"lease-database": {
"type": "memfile",
"persist": true,
"name": "/var/lib/kea/kea-leases4.csv",
"lfc-interval": 3600
},
[...]
"option-data": [
{
"name": "domain-name-servers",
"data": "9.9.9.9, 8.8.8.8"
}
],
[...]
// For a list of available hook libraries, see
https://gitlab.isc.org/isc-projects/kea/wikis/Hooks-available
"hooks-libraries": [
{
"library": "/usr/lib64/kea/hooks/libdhcp_ha.so",
"parameters": {
"high-availability": [
{
"this-server-name": "dhcp01",
"mode": "load-balancing",
"peers": [
{
"name": "dhcp01",
"url": "http://10.1.9.2:8080/";,
"role": "primary"
},
{
"name": "dhcp02",
"url": "http://10.1.9.3:8080/";,
"role": "secondary"
}
]
}
]
}
}
],
"subnet4": [
{
// "name": "Networks",
"option-data": [
{
"data": "1.2.3.1",
"name": "routers"
}
],
"pools": [{"pool": "1.2.3.2 - 1.2.4.254"}],
"reservations": [],
"subnet": "1.2.3.0/23",
"relay": {
"ip-addresses": [ "1.2.3.1","1.2.5.1" ]
}
},
[...]
I moved the subnet4 stanza for the 1.2.3.1/23 pool to a shared-network
stanza and added a new /26 that looks like:
[...]
"shared-networks": [
{
"name": "BNG-Users1",
"relay": {
"ip-addresses": [ "1.2.3.1","1.2.5.1" ]
},
"subnet4": [
{
// "name": "Customer Network Prefix #2",
"option-data": [
{
"data": "1.2.5.1",
"name": "routers"
}
],
"pools": [{"pool": "1.2.5.2 - 1.2.5.62"}],
"reservations": [],
"subnet": "1.2.5.0/26",
"id": 5
},
{
// "name": "Customer Network Prefix #1",
"option-data": [
{
"data": "1.2.3.1",
"name": "routers"
}
],
"pools": [{"pool": "1.2.3.2 - 1.2.4.254"}],
"reservations": [],
"subnet": "1.2.3.0/23",
"id": 110
}
]
}
],
[...]
In starting this up, it hands out the /26 pool and then doesn't assign
much (6 to 12) from the old /23 pool. Reversing the prefixes will mean
it will only assign perhaps a dozen leases and then stops.
Running TCPDUMP on the Kea VMs I see a bunch of broken DHCP handshakes
where I see:
DHCP Discover
DHCP Offer
and not the full handshake of:
DHCP Discover
DHCP Offer
DHCP Request
DHCP ACK
Or I will see a number of Discover/Offer exchanges and after some time a
Discover/Offer/Request/ACK.
If I look at the API with something like:
curl -X POST -H "Content-Type: application/json" -d '{ "command":
"stat-lease4-get","service": [ "dhcp4" ]}' http://127.0.0.1:8080/ |
python3 -m json.tool
[
{
"arguments": {
"result-set": {
"columns": [
"subnet-id",
"total-addreses",
"assigned-addreses",
"declined-addreses"
],
"rows": [
[
1,
509,
499,
0
],
[
2,
967,
0,
0
],
[
3,
1013,
219,
0
],
[
4,
1013,
0,
0
]
],
"timestamp": "2020-11-13 06:08:34.067055"
}
},
"result": 0,
"text": "stat-lease4-get[all subnets]: 4 rows found"
}
]
This is an example of a working dhcp server. If I try the
shared-networks, the pools always show 0 assigned-addresses.
Is shared-networks pretty stable on 1.6.2? Any suggestion on why only a
small percent or none of these handshakes work? Any suggestion on
debugging this further? I did create some rather large kea logs with
logging set to DEBUG and debug set to 99 if that can be of help.
Tim Pozar
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