Multiple DHCPREQUEST/DHCPACK logged for a single DHCPtransaction. Anyone seen this before?
Chuck Anderson
cra at WPI.EDU
Fri Nov 16 14:51:14 UTC 2007
On Fri, Nov 16, 2007 at 08:56:42AM -0500, Steve van der Burg wrote:
> Does anyone know if this indicates that my network is messed up
> somehow? Servers are a partner pair running ISC DHCPd 3.0.5.
> Network is quite large, and I don't run or configure it. I've
> always wondered about the two incoming gateway(?) addresses on the
> requests (.250 and .251). Our official router gateways are all
> .254.
>
> Is this at all normal? These entries have been edited to remove the
> server name and log facility, but are otherwise posted intact:
>
> Nov 16 08:42:27 dhcpd: DHCPREQUEST for 10.136.76.177 from 00:1a:4b:39:11:54 (ABC123) via 10.136.76.250
> Nov 16 08:42:27 dhcpd: DHCPACK on 10.136.76.177 to 00:1a:4b:39:11:54 (ABC123) via 10.136.76.250
> Nov 16 08:42:27 dhcpd: DHCPREQUEST for 10.136.76.177 from 00:1a:4b:39:11:54 (ABC123) via 10.136.76.251
> Nov 16 08:42:27 dhcpd: DHCPACK on 10.136.76.177 to 00:1a:4b:39:11:54 (ABC123) via 10.136.76.251
> Nov 16 08:42:27 dhcpd: DHCPREQUEST for 10.136.76.177 from 00:1a:4b:39:11:54 (ABC123) via 10.136.76.250
> Nov 16 08:42:27 dhcpd: DHCPACK on 10.136.76.177 to 00:1a:4b:39:11:54 (ABC123) via 10.136.76.250
> Nov 16 08:42:27 dhcpd: DHCPREQUEST for 10.136.76.177 from 00:1a:4b:39:11:54 (ABC123) via 10.136.76.251
> Nov 16 08:42:27 dhcpd: DHCPACK on 10.136.76.177 to 00:1a:4b:39:11:54 (ABC123) via 10.136.76.251
It could be that your routers are running VRRP or some similar
redundancy protocol, and the .250/.251 are the physical addresses,
with .254 being the virtual. In my setup, the DHCP relay agents use
the physical addresses, not the virtual. I get twice the number of
relayed DHCP packets that way, and it is normal/works fine.
> Nov 16 08:42:29 dhcpd: DHCPACK to 10.136.76.177 (00:1a:4b:39:11:54) via eri0
> Nov 16 08:42:29 dhcpd: DHCPACK to 10.136.76.177 (00:1a:4b:39:11:54) via eri0
...
This does seem to be an excessive number of consecutive ACKs, though.
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