Multiple DHCPREQUEST/DHCPACK logged for a single DHCPtransaction. Anyone seen this before?

[Chuck Anderson]

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.