Edit:

Disregard the part about option 54. Upon further consideration, it likely has 
nothing at all to due with the issue of responses having a srcIP of the 
incoming interface, instead of the outgoing interface.

Thanks in advance for any tips!

> On Sep 13, 2017, at 1:34 PM, Jason Lixfeld <[email protected]> wrote:
> 
> Hi,
> 
> I have a use case where requests are received on one interface, and responses 
> are transmitted on another interface.  In ISC, this seems to have always 
> worked as expected, but in Kea, it seems that responses are transmitted with 
> the srcIP of the receiving interface, instead of the srcIP of the interface 
> that is expected to transmit the response.
> 
> i.e.:
> 
> 13:06:46.816502 IP (tos 0x0, ttl 253, id 48919, offset 0, flags [none], proto 
> UDP (17), length 349)
>    10.219.45.114.67 > 10.219.66.10.67: [udp sum ok] BOOTP/DHCP, Request from 
> 00:01:47:2d:7a:d0, length 321, hops 1, xid 0x1e875e1f, Flags [none] (0x0000)
>         Gateway-IP 10.63.255.1
>         Client-Ethernet-Address 00:01:47:2d:7a:d0
>         Vendor-rfc1048 Extensions
>           Magic Cookie 0x63825363
>           DHCP-Message Option 53, length 1: Discover
>           Client-ID Option 61, length 8: "0298056"
>           Requested-IP Option 50, length 4: 10.63.255.84
>           Parameter-Request Option 55, length 14:
>             Subnet-Mask, Default-Gateway, Domain-Name-Server, Hostname
>             Domain-Name, BR, Lease-Time, DHCP-Message
>             Server-ID, TFTP, NTP, Time-Zone
>             Option 120, Classless-Static-Route
>           Vendor-Class Option 60, length 20: "ZNID-GE-2628A-00-0GN"
>           Agent-Information Option 82, length 21:
>             Circuit-ID SubOption 1, length 6: ^@^D^L7^B^B
>             Remote-ID SubOption 2, length 11: ^A^Irgw01.lab
>           END Option 255, length 0
> 13:06:46.824359 IP (tos 0x0, ttl 64, id 43882, offset 0, flags [DF], proto 
> UDP (17), length 376)
>    10.219.66.10.67 > 10.63.255.1.67: [bad udp cksum 0x579b -> 0x037e!] 
> BOOTP/DHCP, Reply, length 348, hops 1, xid 0x1e875e1f, Flags [none] (0x0000)
>         Your-IP 10.63.255.84
>         Gateway-IP 10.63.255.1
>         Client-Ethernet-Address 00:01:47:2d:7a:d0
>         Vendor-rfc1048 Extensions
>           Magic Cookie 0x63825363
>           Subnet-Mask Option 1, length 4: 255.255.255.0
>           Domain-Name-Server Option 6, length 8: 66.207.192.4,206.223.173.6
>           Lease-Time Option 51, length 4: 60
>           DHCP-Message Option 53, length 1: Offer
>           Server-ID Option 54, length 4: 10.219.66.10
>           RN Option 58, length 4: 900
>           RB Option 59, length 4: 1800
>           Client-ID Option 61, length 8: "0298056"
>           TFTP Option 66, length 11: "10.63.255.1"
>           Classless-Static-Route Option 121, length 16: 
> (10.32.0.0/24:10.63.255.1),(10.32.11.0/24:10.63.255.1)
>           Agent-Information Option 82, length 21:
>             Circuit-ID SubOption 1, length 6: ^@^D^L7^B^B
>             Remote-ID SubOption 2, length 11: ^A^Irgw01.lab
>           END Option 255, length 0
> 
> root@kea1:/usr/local/etc/kea# ip route
> default via 10.219.66.1 dev ens32 onlink
> 10.32.0.0/11 dev ens34 scope link
> 10.32.0.32/28 dev ens34 proto kernel scope link src 10.32.0.40
> 10.219.66.0/24 dev ens32 proto kernel scope link src 10.219.66.10
> root@kea1:/usr/local/etc/kea#
> 
> OFFER is being sent to 10.63.255.1, but sourced from 10.219.66.10, when it 
> should be sourced from 10.32.0.40.
> 
> I can’t seem to adjust option 54 to force the server ID (which may be the 
> whole issue to begin with?):
> 
> 2017-09-13 13:31:33.238 DEBUG [kea-dhcp4.bad-packets/522] 
> DHCP4_PACKET_DROP_0007 [hwtype=1 00:01:47:2d:7a:d0], 
> cid=[00:30:32:39:38:30:35:36], tid=0x52055156: failed to process packet: 
> Option 54 already present in this message.
> 
> {
>        "client-class" : "rgw01.lab",
>        "subnet": "10.63.255.0/24",
>        "valid-lifetime": 60,
>        "option-data": [
>                {
>                        "name": "domain-name-servers",
>                        "code": 6,
>                        "space": "dhcp4",
>                        "csv-format": true,
>                        "data": "66.207.192.4, 206.223.173.6"
>                },
>                {
>                        "name": "tftp-server-name",
>                        "data": "10.63.255.1"
>                },
>                {
>                        "name" : "dhcp-server-identifier",
>                        "code" : 54,
>                        "space" : "dhcp4",
>                        "csv-format" : true,
>                        "data" : "10.63.255.1"
>                },
>                {
>                        "name": "classless-static-routes",
>                        "data": "180A20000A3FFF01180A200B0A3FFF01"
>                }
>        ],
>        "pools": [
>                {
>                        "pool": "10.63.255.2 - 10.63.255.254"
>                }
>        ],
>        "reservations": [
>                {
>                        "flex-id": "010972677730312e6c616200040c370201",
>                        "ip-address": "10.63.255.69",
>                        "boot-file-name": "byor/26xx_current/S0300608"
>                }
>        ]
> }
> 
> 
> Any pointers?
> 
> Thanks!
> 
> 
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