[Kea-users] kea answers to relay using giaddr instead of source address. any way to fix?

Marcin Siodelski marcin at isc.org
Thu Sep 28 09:24:53 UTC 2017


On 28.09.2017 11:14, Sergey Klusov wrote:
> Hi, i'm using kea-dhcp4 version 1.1.0 from epel repo.
> Here is tcpdump:
>
> 13:35:31.734452 IP (tos 0x0, ttl 63, id 0, offset 0, flags [DF], proto
> UDP (17), length 335)
>     x.x.x.156.67 > x.x.x.90.67: [udp sum ok] BOOTP/DHCP, Request from
> f4:8b:32:a3:79:3f, length 307, hops 1, xid 0x88cd169e, secs 2, Flags
> [none] (0x0000)
>           Gateway-IP 100.101.101.1
>           Client-Ethernet-Address f4:8b:32:a3:79:3f
>           Vendor-rfc1048 Extensions
>             Magic Cookie 0x63825363
>             DHCP-Message Option 53, length 1: Discover
>             Client-ID Option 61, length 7: ether f4:8b:32:a3:79:3f
>             MSZ Option 57, length 2: 1500
>             Vendor-Class Option 60, length 18: "android-dhcp-6.0.1"
>             Hostname Option 12, length 17: "MINOTELTE-MiPhone"
>             Parameter-Request Option 55, length 9:
>               Subnet-Mask, Default-Gateway, Domain-Name-Server, Domain-Name
>               MTU, BR, Lease-Time, RN
>               RB
> 13:35:31.736533 IP (tos 0x10, ttl 128, id 0, offset 0, flags [DF], proto
> UDP (17), length 330)
>     x.x.x.90.67 > 100.101.101.1.67: [udp sum ok] BOOTP/DHCP, Reply,
> length 302, hops 1, xid 0x88cd169e, Flags [none] (0x0000)
>           Your-IP 100.101.101.132
>           Gateway-IP 100.101.101.1
>           Client-Ethernet-Address f4:8b:32:a3:79:3f
>           Vendor-rfc1048 Extensions
>             Magic Cookie 0x63825363
>             Subnet-Mask Option 1, length 4: 255.255.255.0
>             Default-Gateway Option 3, length 4: 100.101.101.1
>             Domain-Name-Server Option 6, length 4: x.x.x.10
>             Hostname Option 12, length 17: "MINOTELTE-MiPhone"
>             Lease-Time Option 51, length 4: 86400
>             DHCP-Message Option 53, length 1: Offer
>             Server-ID Option 54, length 4: x.x.x.90
>             Client-ID Option 61, length 7: ether f4:8b:32:a3:79:3f
>
> Agent's giaddr is not reachable by server, why it keeps sending replies
> to it?
> Is there an option to reply to packet's source address?
> _______________________________________________
> Kea-users mailing list
> Kea-users at lists.isc.org
> https://lists.isc.org/mailman/listinfo/kea-users

>From RFC2131:

"If the 'giaddr' field in a DHCP message from a client is non-zero,
   the server sends any return messages to the 'DHCP server' port on the
   BOOTP relay agent whose address appears in 'giaddr'."

I read this as the server is doing what it is supposed to do.

Marcin



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