flaky DHCP

  • Thread starter Thread starter hawat.thufir
  • Start date Start date
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hawat.thufir

Here I'm connecting to a linksys 802.11g router with an Asus WL-330g
802.11g wireless NIC adapter:

Microsoft Windows 2000 [Version 5.00.2195]
(C) Copyright 1985-1999 Microsoft Corp.


C:\>ipconfig /all


Windows 2000 IP Configuration


Host Name . . . . . . . . . . . . : geidiprime
Primary DNS Suffix . . . . . . . :
Node Type . . . . . . . . . . . . : Broadcast
IP Routing Enabled. . . . . . . . : No
WINS Proxy Enabled. . . . . . . . : No
DNS Suffix Search List. . . . . . : vc.shawcable.net


Ethernet adapter 3com:


Connection-specific DNS Suffix . : vc.shawcable.net
Description . . . . . . . . . . . : 3Com EtherLink XL 10/100
PCI TX NIC
(3C905B-TX)
Physical Address. . . . . . . . . : 00-10-4B-70-F1-87
DHCP Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes
IP Address. . . . . . . . . . . . : 192.168.1.101
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 192.168.1.1
DHCP Server . . . . . . . . . . . : 192.168.1.1
DNS Servers . . . . . . . . . . . : 64.59.144.92
64.59.144.93
Lease Obtained. . . . . . . . . . : Thursday, April 20, 2006
10:20:17 AM


Lease Expires . . . . . . . . . . : Friday, April 21, 2006
10:20:17 AM


C:\>ping 192.168.1.1


Pinging 192.168.1.1 with 32 bytes of data:


Reply from 192.168.1.1: bytes=32 time<10ms TTL=64
Reply from 192.168.1.1: bytes=32 time<10ms TTL=64
Reply from 192.168.1.1: bytes=32 time<10ms TTL=64
Reply from 192.168.1.1: bytes=32 time<10ms TTL=64


Ping statistics for 192.168.1.1:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 0ms, Maximum = 0ms, Average = 0ms


C:\>ping www.google.com


Pinging www.l.google.com [66.102.7.147] with 32 bytes of data:


Reply from 66.102.7.147: bytes=32 time=40ms TTL=245
Reply from 66.102.7.147: bytes=32 time=40ms TTL=245
Reply from 66.102.7.147: bytes=32 time=60ms TTL=245
Reply from 66.102.7.147: bytes=32 time=40ms TTL=245


Ping statistics for 66.102.7.147:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 40ms, Maximum = 60ms, Average = 45ms


C:\>
C:\>

However, when I replace the Linksys router with an SMC router I'm not
getting a good DHCP address. How do I figure out why not?


thanks,

Thufir
 
However, when I replace the Linksys router with an SMC router I'm not
getting a good DHCP address. How do I figure out why not?
Click to expand...

Does the router separate the DHCP clients from their
server?

If so, then most likely you need to make the setting on
the router that is equivalent to "DHCP Relay" (aka
"IP Helper address" by Cisco, IIRC) or "Bootp
forwarding."

The clients BROADCAST must either be relayed
or forwarded to the DHCP server if they are not on the
same "broadcast domain" (i.e., a router separates them.)

Here I'm connecting to a linksys 802.11g router with an Asus WL-330g
802.11g wireless NIC adapter:

Microsoft Windows 2000 [Version 5.00.2195]
(C) Copyright 1985-1999 Microsoft Corp.


C:\>ipconfig /all


Windows 2000 IP Configuration


Host Name . . . . . . . . . . . . : geidiprime
Primary DNS Suffix . . . . . . . :
Node Type . . . . . . . . . . . . : Broadcast
IP Routing Enabled. . . . . . . . : No
WINS Proxy Enabled. . . . . . . . : No
DNS Suffix Search List. . . . . . : vc.shawcable.net


Ethernet adapter 3com:


Connection-specific DNS Suffix . : vc.shawcable.net
Description . . . . . . . . . . . : 3Com EtherLink XL 10/100
PCI TX NIC
(3C905B-TX)
Physical Address. . . . . . . . . : 00-10-4B-70-F1-87
DHCP Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes
IP Address. . . . . . . . . . . . : 192.168.1.101
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 192.168.1.1
DHCP Server . . . . . . . . . . . : 192.168.1.1
DNS Servers . . . . . . . . . . . : 64.59.144.92
64.59.144.93
Lease Obtained. . . . . . . . . . : Thursday, April 20, 2006
10:20:17 AM


Lease Expires . . . . . . . . . . : Friday, April 21, 2006
10:20:17 AM


C:\>ping 192.168.1.1


Pinging 192.168.1.1 with 32 bytes of data:


Reply from 192.168.1.1: bytes=32 time<10ms TTL=64
Reply from 192.168.1.1: bytes=32 time<10ms TTL=64
Reply from 192.168.1.1: bytes=32 time<10ms TTL=64
Reply from 192.168.1.1: bytes=32 time<10ms TTL=64


Ping statistics for 192.168.1.1:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 0ms, Maximum = 0ms, Average = 0ms


C:\>ping www.google.com


Pinging www.l.google.com [66.102.7.147] with 32 bytes of data:


Reply from 66.102.7.147: bytes=32 time=40ms TTL=245
Reply from 66.102.7.147: bytes=32 time=40ms TTL=245
Reply from 66.102.7.147: bytes=32 time=60ms TTL=245
Reply from 66.102.7.147: bytes=32 time=40ms TTL=245


Ping statistics for 66.102.7.147:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 40ms, Maximum = 60ms, Average = 45ms


C:\>
C:\>
Click to expand...
 
Herb said:
Does the router separate the DHCP clients from their
server?

If so, then most likely you need to make the setting on
the router that is equivalent to "DHCP Relay" (aka
"IP Helper address" by Cisco, IIRC) or "Bootp
forwarding."

The clients BROADCAST must either be relayed
or forwarded to the DHCP server if they are not on the
same "broadcast domain" (i.e., a router separates them.)
Click to expand...
....

It's an SMC Barricade, SMC7004VWBR-CA, router. I'll pass these
questions on to the landlord and SMC :)



thanks,

Thufir
 
...

It's an SMC Barricade, SMC7004VWBR-CA, router. I'll pass these
questions on to the landlord and SMC :)
Click to expand...

Landlord? One has no business running a DHCP server on
someone else's network.

If you share a network with a landload (and presumably other
tenants) then you must not do so without permissions and/or
careful coordination.

DHCP servers (and clients are) promiscuous -- they will offer
addressess to any client, and clients will accept from any
DHCP server.

There is no control by domain or operating system vendor etc.
 
Herb Martin wrote:
....
Landlord? One has no business running a DHCP server on
someone else's network.
Click to expand...
....

My landlord. I recently gave him a new router, here are the results:



computer SMC1 linksys Belkin SMC2
=============================================
A | yes no no
?
B | no yes
?
C | yes no
?


A=landlord (wired)
B=me (802.11b)
C=neighbor (802.11b)


It's not just a technical problem, but political. The landlord
couldn't get either the linksys router nor the belkin router (both
brand new) to work from a *wired* connection for him. Tellingly, I was
able to connect with the linksys router wirelessly.

The landlord is a mechanical engineer, and I asked him to try the
linksys router as an experiment (instead of lugging my desktop to
another network). The landlord is the system admin in this scenario,
of course.

The most interesting to me is the first row, that the landlord can't
get the internet from either the linksys or belkin router. I'm
considering trying a brand new SMC router, but expect that column to be
all "no's".


I'm posting this from google, and can only hope that my chart looks
good.

-Thufir
 
It's not just a technical problem, but political. The landlord
couldn't get either the linksys router nor the belkin router (both
brand new) to work from a *wired* connection for him. Tellingly, I was
able to connect with the linksys router wirelessly.
Click to expand...

One person needs to be responsible for coordinating
DHCP and Router configuration.

(Even in a large company with multiple admins, one
senior admin or manager needs to have final say and
authority to resolve disputes or assign responsibility.)
The most interesting to me is the first row, that the landlord can't
get the internet from either the linksys or belkin router. I'm
considering trying a brand new SMC router, but expect that column to be
all "no's".
Click to expand...

Likely all of them will work if properly configured.

Key point: Routing is a more basic issue than DHCP so
you must FIRST get routing correct.

Second, get the DHCP correct and make any needed changed
to the router to assist with this.

DHCP assistance from the router is largely independent of
routing -- so inability to "get the Internet" is must be removed
as a pure routing problem, and once this works you must
ensure the DHCP assignments allow using that (already known
to be functioning) routing.

Herb Martin wrote:
...
...

My landlord. I recently gave him a new router, here are the results:



computer SMC1 linksys Belkin SMC2
=============================================
A | yes no no
?
B | no yes
?
C | yes no
?


A=landlord (wired)
B=me (802.11b)
C=neighbor (802.11b)


It's not just a technical problem, but political. The landlord
couldn't get either the linksys router nor the belkin router (both
brand new) to work from a *wired* connection for him. Tellingly, I was
able to connect with the linksys router wirelessly.

The landlord is a mechanical engineer, and I asked him to try the
linksys router as an experiment (instead of lugging my desktop to
another network). The landlord is the system admin in this scenario,
of course.

The most interesting to me is the first row, that the landlord can't
get the internet from either the linksys or belkin router. I'm
considering trying a brand new SMC router, but expect that column to be
all "no's".


I'm posting this from google, and can only hope that my chart looks
good.
Click to expand...
 
Herb Martin wrote:
....
Likely all of them will work if properly configured.

Key point: Routing is a more basic issue than DHCP so
you must FIRST get routing correct.
Click to expand...
....


I want to test two different routers such that:

SMC1 SMC2
A yes yes
B no yes

A=network admin (wired)
B=me (802.11b)

Which the network admin is willing to set up, and has tried twice so
far (with the linksys and belkin routers). Each time, A says that he
can't get the internet and reboots his computer. I've asked him for
output from ipconfig /all for A but it's not forthcoming, so I'm not
able to provide much data.

How is the routing of the router tested? That is, how can I
investigate why A isn't getting "the internet" from the SMC2 router
(which I've yet to procure)? Run task manager to see a firewall/etc?
Totally irrelevant, but I'm running win2k and A is running winXP.



-Thufir
 
Which the network admin is willing to set up, and has tried twice so
far (with the linksys and belkin routers). Each time, A says that he
can't get the internet and reboots his computer. I've asked him for
output from ipconfig /all for A but it's not forthcoming, so I'm not
able to provide much data.
Click to expand...

Then he isn't much of an admin -- while rebooting the computer
might EVENTUALLY be a good move it is typically a near last
resort when you KNOW everything is correct and it still doesn't
work.

Anyone who cannot supply the IPConfig /all, ping, tracert etc
doesn't yet know ANYTHING much less that everything is
correct.
How is the routing of the router tested?
Click to expand...

By ping and tracert UNLESS the router (or an itermediary)
blocks or is suspected of blocking ICMP (used by ping and
tracert.)

If that is the case then one must test routing with simple tools
like Telnet (or better NetCat but this isn't built into Windows
boxes.)
That is, how can I
investigate why A isn't getting "the internet" from the SMC2 router
(which I've yet to procure)?
Click to expand...

Until you see the ipconfig and ping/tracert results you don't have
a router problem. (Really.)

You are wasting your time (and actually ours) until you get the
output of those commands.

Likely your routers are fine -- OR they merely need to be
configured correctly IF they are the source of the problem.

BTW, you use the same types of tools to test the router IF
it has a command line (many small appliance routers don't have
such command lines and you must analyze their config or web
pages by eye.)
Run task manager to see a firewall/etc?
Totally irrelevant, but I'm running win2k and A is running winXP.
Click to expand...

No standard tool on either will stop network access OUTBOUND;
the XP firewall can prevent INBOUND access but that is NOT your
(reported) problem.
 
Herb Martin wrote:
....
Until you see the ipconfig and ping/tracert results you don't have
a router problem. (Really.)

You are wasting your time (and actually ours) until you get the
output of those commands.

Likely your routers are fine -- OR they merely need to be
configured correctly IF they are the source of the problem.

BTW, you use the same types of tools to test the router IF
it has a command line (many small appliance routers don't have
such command lines and you must analyze their config or web
pages by eye.)
Click to expand...
....

I'm not trying to waste anyone's time, certainly not mine!

The network admin was convinced that the problem was on my end, until
we tried the linksys router. To convince him that the problem isn't on
my end I'm just trying to think of a good experiment. Right now I'm
stuck because he can't seem to get any router to work for him, except
the one which doesn't work for me. It's an impasse.

Perhaps if I were to get him to substitute the linksys router again,
then I could get on the internet. I could demonstrate this to the
network admin, and give him my adapter to try on his computer.


-Thufir
 
I'm not trying to waste anyone's time, certainly not mine!
The network admin was convinced that the problem was on my end, until
we tried the linksys router. To convince him that the problem isn't on
my end I'm just trying to think of a good experiment. Right now I'm
stuck because he can't seem to get any router to work for him, except
the one which doesn't work for me. It's an impasse.

Perhaps if I were to get him to substitute the linksys router again,
then I could get on the internet. I could demonstrate this to the
network admin, and give him my adapter to try on his computer.
Click to expand...

If the some routers work and others do not, it is almost
certainly a difference in configuration UNLESS you
purposely gave them different IP addresses (i.e., the
difference in configuration is a desired one) and then
either failed to set the internal clients to use the correct
address or failed to set the (other) adjacent routers
to route to the external address.

You cannot work on routing, DHCP and such without
the list of configurations -- at a minimum the person
(other admin) must be able to read them off but in
general you need to be able to SEE the configuration
(at least mentally.)

Reports of "doesn't work" are practically worthless.

Useful reports include the specific commands*,
specific results, and specific error messages.

*Specific commands include such detail as "ping
by name" versus "ping by address", and (in the
case of name problems) would include "nslookup
of a specific DNS server" versus defaulting to
the local config without knowing which that is.

When ping "doesn't work" you frequently have to
ASK "by name" or "by address TOO"? That is
a waste of time that could be eliminated by initial
specific reports.

When ping doesn't work, the next step (barring a
known or suspected ICMP filter) is to try TRACERT
to determine "how far" the message travels successfully
(and thus begin to guess/determine the source of the
problem more specifically.) Again, having to say, "If
Ping fails, what about tracert?"

And frequently you may have to specify "by address"
since by the time tracert is needed you are NOT focusing
on a name resolution problem.
 
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