Why is DHCP table empty on Linksys router

Re: Slackware 9.1
On my BEFSR41 there is only one machine currently up... mine. When I go to the
web-based config screen for 198.162.1.1 and I go to Status tab and Local Area
Network and click the DHCP button, there are no machines listed in the table.
Obviously the router assigned me an address but it does not show.

When wife turns on her laptop and logs in, the table only has one entry:
198.162.1.102. What happend to my machine, which I assume is ...101?

Everything seems to work OK, but I would think that my machine would show up
on the table as well?


Al

Al C. wrote:
> Re: Slackware 9.1
> On my BEFSR41 there is only one machine currently up... mine. When I go to the
> web-based config screen for 198.162.1.1 and I go to Status tab and Local Area
> Network and click the DHCP button, there are no machines listed in the table.
> Obviously the router assigned me an address but it does not show.
>
> When wife turns on her laptop and logs in, the table only has one entry:
> 198.162.1.102. What happend to my machine, which I assume is ...101?
>
> Everything seems to work OK, but I would think that my machine would show up
> on the table as well?

Do you forward any services to your box ?
Chances are that it won't show as a dynamic address in that case.

ACK - be careful with "obvious" assumptions!
Do you *know* for a fact that it's using DHCP ?


--
J

All your bits are belong to us - again.

Jeroen Geilman wrote:

> Al C. wrote:
>> Re: Slackware 9.1
>> On my BEFSR41 there is only one machine currently up... mine. When I go to
>> the web-based config screen for 198.162.1.1 and I go to Status tab and
>> Local Area Network and click the DHCP button, there are no machines listed
>> in the table. Obviously the router assigned me an address but it does not
>> show.
>>
>> When wife turns on her laptop and logs in, the table only has one entry:
>> 198.162.1.102. What happend to my machine, which I assume is ...101?
>>
>> Everything seems to work OK, but I would think that my machine would show
>> up on the table as well?
>
> Do you forward any services to your box ?
> Chances are that it won't show as a dynamic address in that case.
>
> ACK - be careful with "obvious" assumptions!
> Do you *know* for a fact that it's using DHCP ?
>
>


This may be the answer. It's from a Usenet posting. I never totally trust
Usenet, but it seems reasonable.


DHCP is really only used when the PCs on your network are turned on and
request an IP address. The DHCP table in the Linksys router (I'm using one
as well) shows the DHCP requests that the router has answered since it was
turned on (or reset). If you reset the router it resets the table, and the
table won't be populated again until a computer is rebooted, or the IP
addresses are released and renewed. This doesn't affect operation, since
the computers on your network already have their IP addresses assigned. You
might run into a problem with IP address conflicts if you have a large
number of computers on your network that are frequently coming on and off,
but DHCP should have a method to resolve this. I'm not familiar enough with
the details of the protocol to know how it handles addressing conflicts.
-----------

The reason that I see the second machine is because it is turned off each
night and rebooted in the AM while my machine is on 24/7 and the DHCP table
"forgets" about it after a lease has expired.... or something like that. I'll
bet that if I reboot my machine it will end up back on the table ... at least
for a while.

Al

In message <(E-Mail Removed)>, Al C. wrote:
>
>
> DHCP is really only used when the PCs on your network are turned on and
> request an IP address. The DHCP table in the Linksys router (I'm using
> one as well) shows the DHCP requests that the router has answered since it
> was
> turned on (or reset). If you reset the router it resets the table, and
> the table won't be populated again until a computer is rebooted, or the IP
> addresses are released and renewed. This doesn't affect operation, since
> the computers on your network already have their IP addresses assigned.
> You might run into a problem with IP address conflicts if you have a large
> number of computers on your network that are frequently coming on and off,
> but DHCP should have a method to resolve this. I'm not familiar enough
> with the details of the protocol to know how it handles addressing
> conflicts. -----------
>
> The reason that I see the second machine is because it is turned off each
> night and rebooted in the AM while my machine is on 24/7 and the DHCP
> table "forgets" about it after a lease has expired.... or something like
> that. I'll bet that if I reboot my machine it will end up back on the
> table ... at least for a while.
>
What output do you get on the Linux box from the command:

ps ax | grep dhclient

That'll tell you if you're running the standard DHCP client on it.
--
Dave
mail da (E-Mail Removed) (without the space)
http://www.llondel.org/
So many gadgets, so little time...

Dave {Reply Address in.sig} wrote:

> In message <(E-Mail Removed)>, Al C. wrote:
>>
>>
>> DHCP is really only used when the PCs on your network are turned on and
>> request an IP address. The DHCP table in the Linksys router (I'm using
>> one as well) shows the DHCP requests that the router has answered since it
>> was
>> turned on (or reset). If you reset the router it resets the table, and
>> the table won't be populated again until a computer is rebooted, or the IP
>> addresses are released and renewed. This doesn't affect operation, since
>> the computers on your network already have their IP addresses assigned.
>> You might run into a problem with IP address conflicts if you have a large
>> number of computers on your network that are frequently coming on and off,
>> but DHCP should have a method to resolve this. I'm not familiar enough
>> with the details of the protocol to know how it handles addressing
>> conflicts. -----------
>>
>> The reason that I see the second machine is because it is turned off each
>> night and rebooted in the AM while my machine is on 24/7 and the DHCP
>> table "forgets" about it after a lease has expired.... or something like
>> that. I'll bet that if I reboot my machine it will end up back on the
>> table ... at least for a while.
>>
> What output do you get on the Linux box from the command:
>
> ps ax | grep dhclient
>
> That'll tell you if you're running the standard DHCP client on it.


al@xxxxxx:~$ ps ax | grep dhcp
226 ? S 0:10 /sbin/dhcpcd -t 10 -d eth0

I wonder if I bring down the dhcp daemon and bring it up again, if I would get
a new IP. I know how to kill it, but not sure how to restart it. the 'man'
page is confusing.

This is just an academic exercise. Everything works fine.

Al

"Al C." <(E-Mail Removed)> wrote in message news:<(E-Mail Removed)>...
> Dave {Reply Address in.sig} wrote:
>
[snip]
> >>
> >> The reason that I see the second machine is because it is turned off each
> >> night and rebooted in the AM while my machine is on 24/7 and the DHCP
> >> table "forgets" about it after a lease has expired.... or something like
> >> that. I'll bet that if I reboot my machine it will end up back on the
> >> table ... at least for a while.

Your machine "renews" its lease at 1/2 the lease time -- and if that
fails, attempts made at 1/2 remaining time, etc., till lease really
does expire. Renewals and Discovery/requests are different ...

> > What output do you get on the Linux box from the command:
> >
> > ps ax | grep dhclient
> >
> > That'll tell you if you're running the standard DHCP client on it.
>
>
> al@xxxxxx:~$ ps ax | grep dhcp
> 226 ? S 0:10 /sbin/dhcpcd -t 10 -d eth0
>
> I wonder if I bring down the dhcp daemon and bring it up again, if I would get
> a new IP. I know how to kill it, but not sure how to restart it. the 'man'
> page is confusing.

When using dhcp, all you need to do is ifdown ethx followed by ifup
ethx -- bringing down the demon alone won't accomplish much ;-)

> This is just an academic exercise. Everything works fine.
>
> Al

If the man page confuses you -- it is rather sparse on background --
try this:
http://www.tldp.org/HOWTO/DHCP/index.html

Also page 17 of your user's guide gives a _very_ brief summary of how
the Linksys router can/is configured as a dhcp server -- note that it
gives out private IPs 192.168.1.X.and is not acting as just a dhcp
relay agent (like many broadband modems and soho routers do). This
also requires it to act as a NAT device -- it's the router that has
the actual, "real" IP from your ISP.

If the post you quoted is near accurate, the table and what it might
be used for is unclear -- it doesn't affect operation (ie., leases).
Perhaps useful if a freshly booted PC fails to get an IP from the
router?

hth,
prg
email above disabled