[Kea-users] Multiple shared subnets

[Friedrich Weissing]

Greetings,

I work for an ISP and we are considering moving away from our current DHCP solution to ISC-DHCP or to KEA.

We would prefer to use KEA as the old ISC-DHCP will be EOL at some point.

I am having issues with my config. We have many vlans, each with multiple subnets on them that need to be able to relay DHCP requests to KEA. I have tried this with Kea version 1.6.2 and with the new 1.7 verision

"shared-networks": [{
"name": "VLAN4067",
"relay": {
             # This relay address is inherited by both subnets.
            "ip-addresses": [ "192.168.28.1" ]
                },
"subnet4": [
  {
      "pools": [ { "pool":  "192.168.28.2 - 192.168.28.2" } ],
      "subnet": "192.168.28.0/30",
        "option-data": [
                {
                    "name": "routers",
                    "data": "192.168.28.1"
                }
            ]
  },
  {
      "pools": [ { "pool": "192.168.28.10 - 192.168.28.14" } ],
        "subnet": "192.168.28.8/29",
        "option-data": [
                {
                    "name": "routers",
                    "data": "192.168.28.9"
                }
            ]
  },
  {
      "pools": [ { "pool": "192.168.28.18 - 192.168.28.30" } ],
      "subnet": "192.168.28.16/28",
        "option-data": [
                {
                    "name": "routers",
                    "data": "192.168.28.17"
                }
            ]
  }]
},
{
"name": "VLAN4068",
"relay": {
             # This relay address is inherited by both subnets.
            "ip-addresses": [ "192.168.28.5" ]
},
"subnet4": [
  {
      "pools": [ { "pool":  "192.168.28.6 - 192.168.28.6" } ],
      "subnet": "192.168.28.4/30",


        "option-data": [
                {
                    "name": "routers",
                    "data": "192.168.28.5"
                }
            ]
  }]
}],

I have tried many different variations of the above config and each produces a different error message/issue.
With this version it will hand out IP addresses from the first subnet4/192.168.28.1 relay IP but it will not hand out an IP from the 192.168.28.5 relay IP.

When I relay the requests from 192.168.28.5 I just get this in my DHCP log.

"Failed to allocate an IPv4 address for client with classes"

For those not familiar with having multiple subnets on a VLAN it looks like this.

!
interface Vlan4067
description "Test DHCP FCW"
bandwidth 10000000
ip dhcp relay information trusted
ip address 192.168.28.1 255.255.255.252 secondary
ip address 192.168.28.5 255.255.255.252
ip helper-address 192.168.22.234
arp timeout 300
end

I also tried this config for kea.

"shared-networks": [{
"name": "VLAN4067",
"relay": {
            "ip-addresses": [ "192.168.28.1" ]
                },
"subnet4": [
  {
      "pools": [ { "pool":  "192.168.28.2 - 192.168.2" } ],
      "subnet": "192.168.28.0/30",
        "option-data": [
                {
                    "name": "routers",
                    "data": "192.168.28.1"
                }
            ]
  },
  {
      "pools": [ { "pool": "192.168.10 - 192.168.28.14" } ],
      "subnet": "192.168.28.8/29",
        "option-data": [
                {
                    "name": "routers",
                    "data": "192.168.28.9"
                }
            ]
  },
  {
      "pools": [ { "pool": "192.168.28.18 - 192.168.28.30" } ],
      "subnet": "192.168.28.16/28",
        "option-data": [
                {
                    "name": "routers",
                    "data": "192.168.28.17"
                }
            ]
  }]
}],



"shared-networks": [{
"name": "test",
"relay": {
            "ip-addresses": [ "192.168.28.5" ]
},
"subnet4": [
  {
      "pools": [ { "pool":  "192.168.6 - 192.168.28.6" } ],
      "subnet": "192.168.28.4/30",
        "option-data": [
               {
                    "name": "routers",
                    "data": "192.168.28.5"
                }
            ]
  }]
}],

With this config I get this error in my kea log.

"DHCP4_PACKET_NAK_0001 [hwtype=1 cc:be:59:XX:XX:XXX], cid=[no info], tid=0x3f0630e4: failed to select a subnet for incoming packet, src 192.168.28.1, type DHCPDISCOVER"

If have tried many different configs and so far I can't get the multiple shared networks to differentiate between each other based on relay IP.

Has anyone set up a network along these lines before that would be willing to give me some pointers?

Sincerely,

<https://www.hbci.com/>
Friedrich Weissing
Network Analyst
Email: fweissing at exchange.hbci.com
Phone: (507)474-5830

 www.hbci.com<https://www.hbci.com/> | (888) 474-9995

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