[Kea-users] Moving to implementing shared-networks
Tim Požár
pozar at lns.com
Thu Jan 7 22:24:54 UTC 2021
Just to follow up with folks on the list.
We were able to get shared networks to work. Seems there were a couple
of problems in the implantation.
1] Index your subnet (id:) and don't let Kea auto-index them.
This bit us a couple of times in moving between configurations.
2] Shared Networks need to split the pool space up between HA servers.
This was not intuitive as we had an HA arrangement where we were not
splitting the pool space up between the servers. Taking a /24 pool
space and splitting that up into two /25 where each server was handling
one of them made things work.
Oh... There is one more thing here. Kea is pretty stringent about JSON
formatting. What we ended up doing to debug that was to stand up
another Kea server that was not a production box to "lint" the config on
before rolling out on a production box.
If folks want to see an example config that works, reply back and I will
send out a "sanitized" version of what we are using.
Tim
On 11/16/20 10:23 AM, Tim Požár wrote:
> Peter...
>
> Thanks for getting back on this. Alas, I had my head in a data center
> this weekend.
>
> We started off with no IDs in the non-shared example and found that
> moving to the shared example and adding the new prefix, we had a
> conflict with the leases db. In looking through the documentation, it
> suggested we assign Ids to pools, which make sense. That was added to
> avoid the conflict in the prefixes.
>
> The API call I demonstrated was for the non-shared config in showing that
> we were able to get leases out that way. Alas, I didn't keep the result
> from the API call when we tried to move to a shared-networks config. My
> bad.
>
> I do have PCAP files for both servers from the time we were trying to
> deploy this. Would that be helpful?
>
> Tim
>
> On 11/14/20 1:27 AM, Peter Davies wrote:
>> Hi Tim,
>> I notice that you are using "subnet id"s in the "shared network"
>> example whereas in your non "shared network example there appears to
>> be no "subnet id"s.
>> Also the "subnet id"s returned in "stat-lease4-get" call don't seem to
>> match your config?
>> If you are seeing relayed "offers" being sent from Kea but no
>> "requests" being received then either
>>
>> 1. The offers are not getting through to the client
>> 2. The requests from the client are not get back to Kea
>> 3. The client doesn't like the offer and does not send a request or it
>> has received an offer from some other source that it requests. If
>> the reason is that the client for some reason does not like the
>> offer then you should be seeing multiple discoveries from the client
>> Clients that already have leases should be unicasting renewal requests
>> directly to Kea.
>>
>> /Peter
>>
>> Sent from Outlook <http://aka.ms/weboutlook>
>> ------------------------------------------------------------------------
>> *From:* Kea-users <kea-users-bounces at lists.isc.org> on behalf of Tim
>> Požár <pozar at lns.com>
>> *Sent:* 14 November 2020 02:05
>> *To:* Kea-users at lists.isc.org <Kea-users at lists.isc.org>
>> *Subject:* [Kea-users] Moving to implementing shared-networks
>> 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
>> <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/
>> <http://10.1.9.2:8080/>",
>> "role": "primary"
>> },
>> {
>> "name": "dhcp02",
>> "url": "http://10.1.9.3:8080/
>> <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/
>> <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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