DHCP clients; where does the preffered routes come from?

Where do my DHCP clients pick up the gate way to point to the 192.168.2.5?

Is the default gateway that is configure in the IP address of the DNS
server passed on to the DHCP clients?

I have 3 router on a network some clients have configured different IP
address for their Default gateway.

Scenario:
Subnet 1: 192.168.1.x has DHCP server and clients
subnet 2: 192.168.2.x has DNS server
Two routers on subnet two 192.168.2.5 and 192.168.2.10.
The DHCP clients on subnet 1 can attach to shared resource of those clients
on subnet 2 that have been configured with a default gateway of 192.168.2.5
but the DHCP clients can not access client on subnet 2 with default gateway
of 192.168.2.10.
If the clients with Gateways of 192.168.2.10 are reconfigured with a GW of
192.168.2.5 the DHCP clients can access the resources.
If the clients with a GW of 192.168.2.10 have a "Route add" pointing to the
gate way ( not shown in this scenario) to get to the 192.168.1.x network.
Than the DHCP clients on 192.168.1.x can access the resources.

My question than is it looks like my DHCP clients are picking up a preferred
gateway of 192.168.2.5 where is this value coming from, if my DHCP clients
are on a subnet 192.168.1.X?

Your DHCP clients in the 192.168.1 subnet will be getting a default
gateway from DHCP. That default gateway must be a 192.168.1.x address. The
default gateway must be "reachable" - ie it must be on the same segment and
in the same IP subnet as the host machine.

The problem you are seeing will be caused by the default gateway
settings on the machines in the 192.168.2 subnet. The traffic from a
machine in the 192.168.1 subnet will go to the router which is defined as
the default gateway for the subnet. This router will deliver the packet to
the target machine in the 192.168.2 subnet.

The problem is then how does that machine send a reply back to the
192.168.1 subnet? As you say, if you give them a default gateway of
192.168.2.5 it will work. It will also work if you add a route to the target
machine to send traffic for 192.168.1 to that address.

I presume you want to leave the machines in 192.168.2 pointing to
192.168.2.10 as their default gateway but still be able to "see" the
machines in 192.168.1 ? The simplest way to achieve this is to add a static
route to the router at 192.168.2.10 . All traffic goes to that router by
default. Add a static route to it to "bounce" the local traffic to the
router at 192.168.2.5 . eg

192.168.1.0 255.255.255.0 192.168.2.5


vidro wrote:
> Where do my DHCP clients pick up the gate way to point to the
> 192.168.2.5?
>
> Is the default gateway that is configure in the IP address of the DNS
> server passed on to the DHCP clients?
>
> I have 3 router on a network some clients have configured different IP
> address for their Default gateway.
>
> Scenario:
> Subnet 1: 192.168.1.x has DHCP server and clients
> subnet 2: 192.168.2.x has DNS server
> Two routers on subnet two 192.168.2.5 and 192.168.2.10.
> The DHCP clients on subnet 1 can attach to shared resource of those
> clients on subnet 2 that have been configured with a default gateway
> of 192.168.2.5 but the DHCP clients can not access client on subnet 2
> with default gateway of 192.168.2.10.
> If the clients with Gateways of 192.168.2.10 are reconfigured with a
> GW of 192.168.2.5 the DHCP clients can access the resources.
> If the clients with a GW of 192.168.2.10 have a "Route add" pointing
> to the gate way ( not shown in this scenario) to get to the
> 192.168.1.x network. Than the DHCP clients on 192.168.1.x can access
> the resources.
>
> My question than is it looks like my DHCP clients are picking up a
> preferred gateway of 192.168.2.5 where is this value coming from, if
> my DHCP clients are on a subnet 192.168.1.X?

I may not have articulated my concern correctly.

I understand that my DHCP clients are going to get a default gateway in
their same subnet. GW 192.168.1.10

The gateway to get to the 192.168.1.x subnet from 192.168.2x subnet is
192.168.2.20 but I have 2 other interfaces 192.168.2.5 and 192.168.2.10 that
are actually my default gateways. I have gateways, plural because I am
testing performance and bottle necks, both gateways go to the same place just
different interfaces.

None of the computers in the 192.168.2.x subnet will point to 192.168.2.20
as a default gateway.
They will either point to 192.168.2.5 or 192.168.2.10 for GW

Again, to get to the 192.168.1.x subnet you have to go through 192.168.2.20.

Now this being the case why are those computers pointing to 192.168.2.5 able
to be access by the DHCP clients on 192.168.1.x subnet and those computer
that are configured with 192.168.2.10 GW can not be accessed by the DHCP
clients except with a manually added �route add�?

I know that these computers are picking up routing tables, I guess that
question is more of where?
Both these interface that are used as default gateways have the same values
in their routing tables.


"Bill Grant" wrote:

> Your DHCP clients in the 192.168.1 subnet will be getting a default
> gateway from DHCP. That default gateway must be a 192.168.1.x address. The
> default gateway must be "reachable" - ie it must be on the same segment and
> in the same IP subnet as the host machine.
>
> The problem you are seeing will be caused by the default gateway
> settings on the machines in the 192.168.2 subnet. The traffic from a
> machine in the 192.168.1 subnet will go to the router which is defined as
> the default gateway for the subnet. This router will deliver the packet to
> the target machine in the 192.168.2 subnet.
>
> The problem is then how does that machine send a reply back to the
> 192.168.1 subnet? As you say, if you give them a default gateway of
> 192.168.2.5 it will work. It will also work if you add a route to the target
> machine to send traffic for 192.168.1 to that address.
>
> I presume you want to leave the machines in 192.168.2 pointing to
> 192.168.2.10 as their default gateway but still be able to "see" the
> machines in 192.168.1 ? The simplest way to achieve this is to add a static
> route to the router at 192.168.2.10 . All traffic goes to that router by
> default. Add a static route to it to "bounce" the local traffic to the
> router at 192.168.2.5 . eg
>
> 192.168.1.0 255.255.255.0 192.168.2.5
>
>
> vidro wrote:
> > Where do my DHCP clients pick up the gate way to point to the
> > 192.168.2.5?
> >
> > Is the default gateway that is configure in the IP address of the DNS
> > server passed on to the DHCP clients?
> >
> > I have 3 router on a network some clients have configured different IP
> > address for their Default gateway.
> >
> > Scenario:
> > Subnet 1: 192.168.1.x has DHCP server and clients
> > subnet 2: 192.168.2.x has DNS server
> > Two routers on subnet two 192.168.2.5 and 192.168.2.10.
> > The DHCP clients on subnet 1 can attach to shared resource of those
> > clients on subnet 2 that have been configured with a default gateway
> > of 192.168.2.5 but the DHCP clients can not access client on subnet 2
> > with default gateway of 192.168.2.10.
> > If the clients with Gateways of 192.168.2.10 are reconfigured with a
> > GW of 192.168.2.5 the DHCP clients can access the resources.
> > If the clients with a GW of 192.168.2.10 have a "Route add" pointing
> > to the gate way ( not shown in this scenario) to get to the
> > 192.168.1.x network. Than the DHCP clients on 192.168.1.x can access
> > the resources.
> >
> > My question than is it looks like my DHCP clients are picking up a
> > preferred gateway of 192.168.2.5 where is this value coming from, if
> > my DHCP clients are on a subnet 192.168.1.X?
>
>
>

You cannot have two active default gateways. Even if you set two at the
same priority, the system will only use one of them. So you need to select
which one you want to use as the default, then use static routiong for any
traffic which needs to use some other gateway.

vidro wrote:
> I may not have articulated my concern correctly.
>
> I understand that my DHCP clients are going to get a default gateway
> in their same subnet. GW 192.168.1.10
>
> The gateway to get to the 192.168.1.x subnet from 192.168.2x subnet is
> 192.168.2.20 but I have 2 other interfaces 192.168.2.5 and
> 192.168.2.10 that are actually my default gateways. I have gateways,
> plural because I am testing performance and bottle necks, both
> gateways go to the same place just different interfaces.
>
> None of the computers in the 192.168.2.x subnet will point to
> 192.168.2.20 as a default gateway.
> They will either point to 192.168.2.5 or 192.168.2.10 for GW
>
> Again, to get to the 192.168.1.x subnet you have to go through
> 192.168.2.20.
>
> Now this being the case why are those computers pointing to
> 192.168.2.5 able to be access by the DHCP clients on 192.168.1.x
> subnet and those computer that are configured with 192.168.2.10 GW
> can not be accessed by the DHCP clients except with a manually added
> "route add"?
>
> I know that these computers are picking up routing tables, I guess
> that question is more of where?
> Both these interface that are used as default gateways have the same
> values in their routing tables.
>
>
> "Bill Grant" wrote:
>
>> Your DHCP clients in the 192.168.1 subnet will be getting a
>> default gateway from DHCP. That default gateway must be a
>> 192.168.1.x address. The default gateway must be "reachable" - ie it
>> must be on the same segment and in the same IP subnet as the host
>> machine.
>>
>> The problem you are seeing will be caused by the default gateway
>> settings on the machines in the 192.168.2 subnet. The traffic from a
>> machine in the 192.168.1 subnet will go to the router which is
>> defined as the default gateway for the subnet. This router will
>> deliver the packet to the target machine in the 192.168.2 subnet.
>>
>> The problem is then how does that machine send a reply back to
>> the 192.168.1 subnet? As you say, if you give them a default
>> gateway of 192.168.2.5 it will work. It will also work if you add a
>> route to the target machine to send traffic for 192.168.1 to that
>> address.
>>
>> I presume you want to leave the machines in 192.168.2 pointing to
>> 192.168.2.10 as their default gateway but still be able to "see" the
>> machines in 192.168.1 ? The simplest way to achieve this is to add a
>> static route to the router at 192.168.2.10 . All traffic goes to
>> that router by default. Add a static route to it to "bounce" the
>> local traffic to the router at 192.168.2.5 . eg
>>
>> 192.168.1.0 255.255.255.0 192.168.2.5
>>
>>
>> vidro wrote:
>>> Where do my DHCP clients pick up the gate way to point to the
>>> 192.168.2.5?
>>>
>>> Is the default gateway that is configure in the IP address of the
>>> DNS server passed on to the DHCP clients?
>>>
>>> I have 3 router on a network some clients have configured different
>>> IP address for their Default gateway.
>>>
>>> Scenario:
>>> Subnet 1: 192.168.1.x has DHCP server and clients
>>> subnet 2: 192.168.2.x has DNS server
>>> Two routers on subnet two 192.168.2.5 and 192.168.2.10.
>>> The DHCP clients on subnet 1 can attach to shared resource of those
>>> clients on subnet 2 that have been configured with a default gateway
>>> of 192.168.2.5 but the DHCP clients can not access client on subnet
>>> 2 with default gateway of 192.168.2.10.
>>> If the clients with Gateways of 192.168.2.10 are reconfigured with a
>>> GW of 192.168.2.5 the DHCP clients can access the resources.
>>> If the clients with a GW of 192.168.2.10 have a "Route add" pointing
>>> to the gate way ( not shown in this scenario) to get to the
>>> 192.168.1.x network. Than the DHCP clients on 192.168.1.x can access
>>> the resources.
>>>
>>> My question than is it looks like my DHCP clients are picking up a
>>> preferred gateway of 192.168.2.5 where is this value coming from, if
>>> my DHCP clients are on a subnet 192.168.1.X?

BINGO you said the word I can hone in on "system". What would be considered
the "system".
My DHCP clients get the default gateway that points to the interface
(192.168.1.10) that let's them get to the 192.168.2.x subnet.
Now all the clients on the 192.168.2.x subnet need to know to get to
192.168.1x they have to go to 192.168.2.20
two ways of doing this
1.either manually with "route add"
2. or the router that is configure as the default gateway has a route table
that tells the client were to go.

Really any router interface heading out the 192.168.2.x network could be
considered a default gateway. That preference is up to the Network engineer
(as long as the clients can get to where they need to go).

My question is my DHCP client want to hop 2 subnets, they know what the
local gateway is 192.168.1.10 How do they know what the default gateway is
on the other subnets?
Where does that info come from?

"Bill Grant" wrote:

> You cannot have two active default gateways. Even if you set two at the
> same priority, the system will only use one of them. So you need to select
> which one you want to use as the default, then use static routiong for any
> traffic which needs to use some other gateway.
>
> vidro wrote:
> > I may not have articulated my concern correctly.
> >
> > I understand that my DHCP clients are going to get a default gateway
> > in their same subnet. GW 192.168.1.10
> >
> > The gateway to get to the 192.168.1.x subnet from 192.168.2x subnet is
> > 192.168.2.20 but I have 2 other interfaces 192.168.2.5 and
> > 192.168.2.10 that are actually my default gateways. I have gateways,
> > plural because I am testing performance and bottle necks, both
> > gateways go to the same place just different interfaces.
> >
> > None of the computers in the 192.168.2.x subnet will point to
> > 192.168.2.20 as a default gateway.
> > They will either point to 192.168.2.5 or 192.168.2.10 for GW
> >
> > Again, to get to the 192.168.1.x subnet you have to go through
> > 192.168.2.20.
> >
> > Now this being the case why are those computers pointing to
> > 192.168.2.5 able to be access by the DHCP clients on 192.168.1.x
> > subnet and those computer that are configured with 192.168.2.10 GW
> > can not be accessed by the DHCP clients except with a manually added
> > "route add"?
> >
> > I know that these computers are picking up routing tables, I guess
> > that question is more of where?
> > Both these interface that are used as default gateways have the same
> > values in their routing tables.
> >
> >
> > "Bill Grant" wrote:
> >
> >> Your DHCP clients in the 192.168.1 subnet will be getting a
> >> default gateway from DHCP. That default gateway must be a
> >> 192.168.1.x address. The default gateway must be "reachable" - ie it
> >> must be on the same segment and in the same IP subnet as the host
> >> machine.
> >>
> >> The problem you are seeing will be caused by the default gateway
> >> settings on the machines in the 192.168.2 subnet. The traffic from a
> >> machine in the 192.168.1 subnet will go to the router which is
> >> defined as the default gateway for the subnet. This router will
> >> deliver the packet to the target machine in the 192.168.2 subnet.
> >>
> >> The problem is then how does that machine send a reply back to
> >> the 192.168.1 subnet? As you say, if you give them a default
> >> gateway of 192.168.2.5 it will work. It will also work if you add a
> >> route to the target machine to send traffic for 192.168.1 to that
> >> address.
> >>
> >> I presume you want to leave the machines in 192.168.2 pointing to
> >> 192.168.2.10 as their default gateway but still be able to "see" the
> >> machines in 192.168.1 ? The simplest way to achieve this is to add a
> >> static route to the router at 192.168.2.10 . All traffic goes to
> >> that router by default. Add a static route to it to "bounce" the
> >> local traffic to the router at 192.168.2.5 . eg
> >>
> >> 192.168.1.0 255.255.255.0 192.168.2.5
> >>
> >>
> >> vidro wrote:
> >>> Where do my DHCP clients pick up the gate way to point to the
> >>> 192.168.2.5?
> >>>
> >>> Is the default gateway that is configure in the IP address of the
> >>> DNS server passed on to the DHCP clients?
> >>>
> >>> I have 3 router on a network some clients have configured different
> >>> IP address for their Default gateway.
> >>>
> >>> Scenario:
> >>> Subnet 1: 192.168.1.x has DHCP server and clients
> >>> subnet 2: 192.168.2.x has DNS server
> >>> Two routers on subnet two 192.168.2.5 and 192.168.2.10.
> >>> The DHCP clients on subnet 1 can attach to shared resource of those
> >>> clients on subnet 2 that have been configured with a default gateway
> >>> of 192.168.2.5 but the DHCP clients can not access client on subnet
> >>> 2 with default gateway of 192.168.2.10.
> >>> If the clients with Gateways of 192.168.2.10 are reconfigured with a
> >>> GW of 192.168.2.5 the DHCP clients can access the resources.
> >>> If the clients with a GW of 192.168.2.10 have a "Route add" pointing
> >>> to the gate way ( not shown in this scenario) to get to the
> >>> 192.168.1.x network. Than the DHCP clients on 192.168.1.x can access
> >>> the resources.
> >>>
> >>> My question than is it looks like my DHCP clients are picking up a
> >>> preferred gateway of 192.168.2.5 where is this value coming from, if
> >>> my DHCP clients are on a subnet 192.168.1.X?
>
>
>

That information is set in your DHCP scope options. DHCP doesnt care
what you plug in as the gateway to hand out to clients.

psg

The gateway which DHCP hands out gives the clients the default gateway
for the local subnet. When a client needs to send a packet the decision is
usually simple. If it is on the local subnet, it is delivered directly (on
the wire using hardware addressing). If it is not on the local subnet, the
packet is sent to the default router (or gateway). The client does not know
or care what the next hop is.

The gateway router examines its routing table and redirects the packet
based on that information. If there is a specific route for the packet, that
is used. If there is not, the router's default route is used (and so on for
as many hops as it takes!).

chrispsg wrote:
> That information is set in your DHCP scope options. DHCP doesnt care
> what you plug in as the gateway to hand out to clients.
>
> psg

Good explanation bill... I think his problem lies here:

"My question than is it looks like my DHCP clients are picking up a
preferred
gateway of 192.168.2.5 where is this value coming from, if my DHCP
clients
are on a subnet 192.168.1.X? "

>From the OP it would lead me to believe that he has 192.168.2.5 as a
gateway for clients on the 192.168.1.x subnet. If this is the case
clients on the 192.168.1.x subnets would not be able to reach the
gateway. DHCP needs to give out a gateway that is on the same subnet
then that router needs a route added to the 192.168.2.x subnet.

psg

Negative. Problem does not lie there.

The verbiage is not clear in the explanation.
The DHCP clients picks up the correct default gateway on their subnet
(192.168.1.x) this gets them over to the 192.168.2. x subnet.

If the Internet gateway is on the 192.168.2.x subnet where is my DHCP
clients on the 192.168.1 x subnet picking up the information.


Client is on the 192.168.1.x subnet
DHCP server is on the 192.168.1.x subnet
DNS is on the 192.168.2.x subnet
I-net gateway is on the 192.168.2.x subnet

"chrispsg" wrote:

> Good explanation bill... I think his problem lies here:
>
> "My question than is it looks like my DHCP clients are picking up a
> preferred
> gateway of 192.168.2.5 where is this value coming from, if my DHCP
> clients
> are on a subnet 192.168.1.X? "
>
> >From the OP it would lead me to believe that he has 192.168.2.5 as a
> gateway for clients on the 192.168.1.x subnet. If this is the case
> clients on the 192.168.1.x subnets would not be able to reach the
> gateway. DHCP needs to give out a gateway that is on the same subnet
> then that router needs a route added to the 192.168.2.x subnet.
>
> psg
>
>

"vidro" <(E-Mail Removed)> wrote in message
news:7FB747D1-5D3A-4A2A-B15F-(E-Mail Removed)...
> If the Internet gateway is on the 192.168.2.x subnet where is my DHCP
> clients on the 192.168.1 x subnet picking up the information.

They don't. And they don't need to. The only thing they know is what to use
as a Gateway to leave their own Subnet,...they are not aware, and never will
be aware, of what happens after that. Once they pass the traffic to their
local Gateway the LAN's Routing Scheme takes over and the Clients do not
have any role in the process at all.

--
Phillip Windell [MCP, MVP, CCNA]
www.wandtv.com
-----------------------------------------------------
Understanding the ISA 2004 Access Rule Processing
http://www.isaserver.org/articles/IS...cessRules.html

Microsoft Internet Security & Acceleration Server: Guidance
http://www.microsoft.com/isaserver/t...dance/2004.asp
http://www.microsoft.com/isaserver/t...dance/2000.asp

Microsoft Internet Security & Acceleration Server: Partners
http://www.microsoft.com/isaserver/partners/default.asp

Deployment Guidelines for ISA Server 2004 Enterprise Edition
http://www.microsoft.com/technet/pro...isaserver.mspx
-----------------------------------------------------