Subnet Change Problem, Help?

[Guest]

Archived from groups: microsoft.public.windowsnt.protocol.tcpip (More info?)

Here is the scenario:

On a Windows NT Domain network using TCP/IP with WINS and DHCP in a
Switched network. (Cisco and Extreme switches)

Currently the range of 172.16.200.1 - 172.16.200.38 is Static and given
out to various types of servers. The rest is DHCP with a subnet mask of
255.255.255.0

Recently, in an effort to increase the number of IP addresses available an
attempt was made to change the subnet mask to 255.255.240.0. And new IP
Addresses were given out. These look like 172.16.192.x to 172.16.192.xxx

In general things appeared to work but in effect they didn't. Anything
that had a 172.16.192.??? address couldn't see anything with a
172.16.200.??? address. Yet with the subnet mask we chose they should be
on the same network and should see each other fine.

Now this lack of functioning isn't complete. The lack of connectivity
will come and go. Say I find I have IP address 172.16.192.30 and the
server has IP address 172.16.200.31. Yet I can't ping the server. So I
release my IP address and renew it. Then I can ping the server again.
Yet if a wait a while I won't be able to ping the server. And if I wait a
while longer I can ping the server.

One other item in this mix is we have a Wide Area Network connected
through a Cisco Router. This router is set as the Default Gateway for all
machines.

Anyone have any ideas why these type of issues would be occuring?

Help.

 

[Guest]

Archived from groups: microsoft.public.windowsnt.protocol.tcpip (More info?)

Are you VLANing on the switches?

>-----Original Message-----
>Here is the scenario:
>
>On a Windows NT Domain network using TCP/IP with WINS and
DHCP in a
>Switched network. (Cisco and Extreme switches)
>
>Currently the range of 172.16.200.1 - 172.16.200.38 is
Static and given
>out to various types of servers. The rest is DHCP with a
subnet mask of
>255.255.255.0
>
>Recently, in an effort to increase the number of IP
addresses available an
>attempt was made to change the subnet mask to
255.255.240.0. And new IP
>Addresses were given out. These look like 172.16.192.x
to 172.16.192.xxx
>
>In general things appeared to work but in effect they
didn't. Anything
>that had a 172.16.192.??? address couldn't see anything
with a
>172.16.200.??? address. Yet with the subnet mask we
chose they should be
>on the same network and should see each other fine.
>
>Now this lack of functioning isn't complete. The lack of
connectivity
>will come and go. Say I find I have IP address
172.16.192.30 and the
>server has IP address 172.16.200.31. Yet I can't ping the
server. So I
>release my IP address and renew it. Then I can ping the
server again.
>Yet if a wait a while I won't be able to ping the
server. And if I wait a
>while longer I can ping the server.
>
>One other item in this mix is we have a Wide Area Network
connected
>through a Cisco Router. This router is set as the Default
Gateway for all
>machines.
>
>Anyone have any ideas why these type of issues would be
occuring?
>
>Help.
>.
>

 

[Guest]

Archived from groups: microsoft.public.windowsnt.protocol.tcpip (More info?)

<anonymous@discussions.microsoft.com> wrote in
news:14aff01c444f8$3cb109b0$a101280a@phx.gbl:

> Are you VLANing on the switches?
....

Nope. No Vlan that I know of. But I'm not the guy who set them up. The
guy who set them up is on vacation and hasn't been able to solve the issue
thus far. I wanted to take crack at it.

What role might a Vlan config in the switches play? That does give me a
hint to look at that aspect. 99% of our servers are connected either via
Gig copper or fiber into Extreme Switches. I'll see how I can do onto a
few servers on the Cisco end of things.

I installed the old SMS 1.2 NetMon tool on a laptop and have been trying
to track things down.

The interesting thing is that looking at the traces of the pings failing,
I can see that the source and destination mac addresses are correct. Yet
the pings are failing. Then suddenly they start working after a while. I
can then move onto a different server to ping that doesn't work. Get it
working eventually. Then move on to the server that worked before and now
it doesn't again.

I need to look at the captures further to see if I can find a common
change just before the pings start working.

Thanks.

 

[Guest]

Archived from groups: microsoft.public.windowsnt.protocol.tcpip (More info?)

<anonymous@discussions.microsoft.com> wrote in
news:14aff01c444f8$3cb109b0$a101280a@phx.gbl:

> Are you VLANing on the switches?
....

Here is a recap. In the past the subnet mask on this network was
255.255.255.0. Changing the subnet mask to 255.255.240.0 has created a
problem with any machine that now uses an IP address that varies from
the 172.16.200.XXX range.

Machine A Destination IP 172.16.200.10 (Static)
Destination Subnet Mask 255.255.240.0

Machine B Source IP 172.16.192.30 (Static)
Source Subnet Mask 255.255.240.0

These machines exist on a switched network.

In theory both Machine A and Machine B are on the same network via their subnet mask. Yet a
Ping of Machine A results in a Request timed out.

Using Network Monitor on Machine B I can see the ICMP frames being
issued and I can see that the frames include the proper MAC address for
Machine A as the destination and Machine B as the source. The name, on
Machine A is being resolved properly to an ip address. Yet ping fails.

Below is a summary of the Network Monitor Trace data for 2 of the pings
that fail followed by the first one that works. Notice between the two
that fail (and all that fail previous to this) there is no additional
network traffic occuring. Yet just before the correct one occurs there
is all sorts of new traffic.

So the issue is, what is this traffic doing. And why is it not occuring
immediately and instead waits until well into the attempt at pinging?

Time Src Mac DestMac Protocol Description Src Other Addr Dst Other Addr Type Other Addr

1063.849741 LOCAL MACHINE_B ICMP Echo: From 172.16.192.30 To 172.16.200.17 MACHINE_A 172.16.200.17 IP
1063.849741 LOCAL MACHINE_B ICMP Echo: From 172.16.192.30 To 172.16.200.17 MACHINE_A 172.16.200.17 IP
1064.851181 LOCAL MACHINE_B ICMP Echo: From 172.16.192.30 To 172.16.200.17 MACHINE_A 172.16.200.17 IP
1064.851181 LOCAL MACHINE_B ICMP Echo: From 172.16.192.30 To 172.16.200.17 MACHINE_A 172.16.200.17 IP
1065.712419 LOCAL 00C04F702358 NBT NS: Query req. for DOMAINNAME <1C> MACHINE_A 172.16.200.42 IP
1065.712419 LOCAL 00C04F702358 NBT NS: Query req. for DOMAINNAME <1C> MACHINE_A 172.16.200.42 IP
1065.712419 00C04F702358 *BROADCAST ARP_RARP ARP: Request, Target IP: 172.16.192.30
1065.712419 LOCAL 00C04F702358 ARP_RARP ARP: Reply, Target IP: 172.16.200.42 Target Hdwr Addr: 00C04F702358
1065.712419 LOCAL 00C04F702358 ARP_RARP ARP: Reply, Target IP: 172.16.200.42 Target Hdwr Addr: 00C04F702358
1065.712419 00C04F702358 LOCAL NBT NS: Query (Node Status) resp. for DOMAINNAME <1C>, Success 172.16.200.42 MACHINE_A IP
1065.712419 LOCAL *BROADCAST Netlogon SAM LOGON request from client MACHINE_A DOMAINNAME IP
1065.712419 LOCAL *BROADCAST Netlogon SAM LOGON request from client MACHINE_A DOMAINNAME IP
1065.712419 LOCAL *BROADCAST ARP_RARP ARP: Request, Target IP: 172.16.200.31
1065.712419 LOCAL *BROADCAST ARP_RARP ARP: Request, Target IP: 172.16.200.31
1065.712419 BDC1 LOCAL ARP_RARP ARP: Reply, Target IP: 172.16.192.30 Target Hdwr Addr: 0010A4BC07CE
1065.712419 LOCAL BDC1 Netlogon SAM LOGON request from client MACHINE_A BDC1 IP
1065.712419 PDC1 *BROADCAST ARP_RARP ARP: Request, Target IP: 172.16.192.30
1065.712419 LOCAL PDC1 ARP_RARP ARP: Reply, Target IP: 172.16.200.5 Target Hdwr Addr: 00C04F70237A
1065.712419 LOCAL BDC1 Netlogon SAM LOGON request from client MACHINE_A BDC1 IP
1065.712419 LOCAL PDC1 ARP_RARP ARP: Reply, Target IP: 172.16.200.5 Target Hdwr Addr: 00C04F70237A
1065.712419 PDC1 LOCAL Netlogon SAM Response when user is unknown PDC1 MACHINE_A IP
1065.722434 BDC1 LOCAL Netlogon SAM Response when user is unknown BDC1 MACHINE_A IP
1065.852621 LOCAL MACHINE_B ICMP Echo: From 172.16.192.30 To 172.16.200.17 MACHINE_A 172.16.200.17 IP
1065.852621 LOCAL MACHINE_B ICMP Echo: From 172.16.192.30 To 172.16.200.17 MACHINE_A 172.16.200.17 IP
1065.852621 MACHINE_B LOCAL ICMP Echo Reply: To 172.16.192.30 From 172.16.200.17 172.16.200.17 MACHINE_A IP