Re: newbie to home network dhcp worries

From: Leythos (void_at_nowhere.lan)
Date: 01/09/05 

Date: Sun, 09 Jan 2005 14:41:07 GMT

In article <O2DrZbj9EHA.3504@TK2MSFTNGP12.phx.gbl>, elmoono@yahoo.co.uk
says...
> Hi, i have just connected 3 pc's to a Linksys BEFSR41 router, the router is
> etherneted to a Linksys ADSL2MUE modem. I have changed the routers IP to
> 192.168.2.1 as the modems address is 192.168.1.1
> Both these boxes have a dhcp server - and NAT firewalls. My concern is
> should both boxes be acting as dhcp servers? if not which one is
> prefferable? Should both have the NAT firewall running?
> Any advice suggestions appreciated! I have asked on a couple of home
> networking forums only to come up with different opinions! some say its fine
> to have both as dhcp servers, others say you should not have both doing
> this!
> Thanks

If I understand you correctly you have this setup:

INTERNET <> ADSL2MUE <> BEFSR41 <> Computers

With this setup your ADSL get's an IP from the ISP, the BEFSR41 get's
and IP from the ADSL unit, and the computers get an IP from the BEFSR.

As long as the private side of both ADSL and BEFSR are different
networks you are fine.

You could setup the BEFSR41 to have a Fixed WAN address, but, you would
need to specify the DNS settings. In reality, your setup is not much
different than others, both systems get a leased IP from their parent
and your traffic is working.

Where you may run into trouble is getting inbound traffic from the
internet (for games, VOIP, etc...) to work properly through a double
NAT. You also need to understand that NAT does not make either of these
devices a Firewall, not even close. NAT only blocks unsolicited inbound
traffic to your network.

In your setup, since the ADSL is using NAT, there should be no
unsolicited traffic reaching the BEFSR unit.

I would setup the ADSL unit to pass the public IP through to the BEFSR
unit, meaning that I would not NAT the public IP at the ADSL unit. I
would let the BEFSR unit do the NAT - this way you could install
WallWatcher on a PC and enable logs in the router and watch all in/out
bound traffic for problems.

In summary, as long as both NAT networks are on different subnets
(192.168.1.X and 192.168.2.X with a 255.255.255.0 mask) you will have no
problems, even with DHCP enabled. Both devices are completely capable of
working in a Dynamic mode and will update just fine. 

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