[nSLUG] Eastlink cable modem access

Gerald linux at zdoit.airpost.net
Thu Jan 31 13:51:26 AST 2008


Jon wrote:
. . . .
> Interesting. Granted, I don't spend a lot of time watching DHCP logs, 
> but I would think that the second example is more indicative of a 
> 'normal' DHCP request as it is a broadcast request on port 67. This is 
> designed to hit any DHCP server on the network in the hopes that it will 
> give out an address.
> 
> Given that a computer without an IP address cannot communication on a 
> TCP/IP network. I can't see how a DHCP request to a specific address 
> (like  in your first snippet) would succeed. Perhaps it's a refresh 
> request in that the interface already has an IP assigned to it and can 
> therefore query a specific DHCP server.
> 
> Curious...
> 
> Jon

Jon,

I wasn't looking at the logs until I noticed a connection from my router 
to the 10.6.x.x address on a DHCP port. Then I started looking at the logs.

My understanding of the DHCP protocol is it can/must ask first for a 
renewal from the same DHCP server that offered the address to be 
renewed. That leads to requests to a specific address instead of the 
255.255.255.255 address.

-- 
Gerald



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