DHCP

[Lou]

I'm reasonably sure of what I've observed but that has proven wrong in
the past so ...l.

Environment: Win XP Home, Local lan connected to Linksys Router which
has DHCP function.

Observation: When I configure my system to automatically obtain an IP
address, DHCP is activated. ZoneAlarm shows a lot of outbound
activity being blocked, all UDP. When I configure my sysstem with
static IP address, DHCP is not acitive and ZoneAlarm shows no outbound
traffic being blocked.

It seems there is a small processing price to pay for the slightly
easier manner of Lan configuration.

Am I correct in my observation? Any thoughts?

Thanks

 

[Malke]

I'm reasonably sure of what I've observed but that has proven wrong in
the past so ...l.

Environment: Win XP Home, Local lan connected to Linksys Router which
has DHCP function.

Observation: When I configure my system to automatically obtain an IP
address, DHCP is activated. ZoneAlarm shows a lot of outbound
activity being blocked, all UDP. When I configure my sysstem with
static IP address, DHCP is not acitive and ZoneAlarm shows no outbound
traffic being blocked.

It seems there is a small processing price to pay for the slightly
easier manner of Lan configuration.

Am I correct in my observation? Any thoughts?

Thanks

This has nothing to do with a "lan configuration". DHCP is Dynamic Host
Configuration Protocol. You use it when you want your router to assign
internal IP addresses to the computers on your lan. You can also assign
static IP addresses to computers on your lan if you prefer. This is
normal behavior.

Malke

 

[SlowJet]

For a static AT HOME desktop computer you are probably correct but for a
traveling wireless notebook no.

Imagine you have a home net work and you P/C is really a client connected to
your ISP.
Your client would ask the first computer for a non routable IP through DHCP
and the NAT router proxy firewall combo on the first computer would return
your client an IP and would also be the DSN server for the Client.

So where did the ISP host p/C get it's ip and DSN severs? From the ISP's
computer thru DHCP and DSN.

In affect, your router is like a little computer getting it's IP from the
ISP, and sending you a non routable one. Then it gets the DNS severs ip's
from the ISP and passes them on to you. In the old old days there were only
computers, and some were rounters, some were firewalls, some were proxies.
Now it's all in a little black box.

SJ

 

[Lou]

Observation: When I configure my system to automatically obtain an IP

This has nothing to do with a "lan configuration". DHCP is Dynamic Host
Configuration Protocol. You use it when you want your router to assign
internal IP addresses to the computers on your lan. You can also assign
static IP addresses to computers on your lan if you prefer. This is
normal behavior.

OK.

But why all the blocked traffic after I have already been assigned an
IP address when I configure my P/C to use Dynamic addressing?

There is no blocked traffic if I use static addressing

 

[SlowJet]

Well, this is a good example of not enough details about your network,
router, and ip vs. my assuming you ran the network wizard to open ports on
the WFW.

a.. If you select This computer connects to the Internet through a
residential gateway or through another computer on my network on the Select
a connection method page, the Network Setup Wizard will open the Windows
Firewall ports needed to discover a residential gateway and ensure that
Internet Gateway Device Discovery and Control is running.

Try that, ???

SJ

 

[CZ]

Observation: When I configure my system to automatically obtain an IP
Lou:

Yes.
In general:
For the initial discovery process:
A DHCP client will send a broadcast (UDP) to find a DHCP server.
A DHCP server can respond with an IP address and DHCP options.
The DHCP client can accept the offer.
The DHCP client will broadcast several frames (ARP) to test the exclusivity
of the assigned IP address it accepted.

To renew an existing IP address lease, the DHCP client and DHCP server only
send one UDP packet each. And the DHCP client will broadcast several frames
(ARP) to test the exclusivity of the IP address.


In the ZA log on a DHCP client, you should see source port 68, and
destination port 67 for the outbound UDP activity.

 

[CZ]

In affect, your router is like a little computer getting it's IP from the
SJ:

Just a slight twist:
Private IP addresses are routable, but are not supposed to be routed over
the Internet.

For example: in test setups, I frequently have 10.x.x.x on one side of a
router and 192.168.x.x on the other side.

 

[SlowJet]

Wouldn't that only be needed if you were routing more than one sub net??

Besides, 10 is cheating. lol

So many options.

SJ

 

[CZ]

CZ wrote:
Private IP addresses are routable, but are not supposed to be routed over
the Internet.
For example: in test setups, I frequently have 10.x.x.x on one side of a
router and 192.168.x.x on the other side.

SJ wrote:
Wouldn't that only be needed if you were routing more than one sub net??

SJ:

IMO, you do not "route a subnet", you use an IP router to communicate
between different subnets. If you are only communicating within one subnet,
then a router is not needed.