Routing problem

[Guest]

Hi, I'm newbie to Networking esp. on routing. I have 2 servers connected to different gateways. I couldn't telnet any port from either server but I can ping. Below is the route print of my 2 servers. FYI, I cannot ping either gateways from aither servers. Eg. Sever A can ping it's own gateway but not Server B's gateway.

SERVER A
------------
Active Routes:
Network Destination Netmask Gateway Interface Metric
0.0.0.0 0.0.0.0 172.16.23.1 172.16.23.34 1
127.0.0.0 255.0.0.0 127.0.0.1 127.0.0.1 1
172.16.23.0 255.255.255.128 172.16.23.34 172.16.23.34 1
172.16.23.34 255.255.255.255 127.0.0.1 127.0.0.1 1
172.16.255.255 255.255.255.255 172.16.23.34 172.16.23.34 1
192.16.3.16 255.255.255.240 172.16.23.80 172.16.23.34 1
192.168.3.16 255.255.255.240 172.16.23.18 172.16.23.34 1
224.0.0.0 224.0.0.0 172.16.23.34 172.16.23.34 1
255.255.255.255 255.255.255.255 172.16.23.34 172.16.23.34 1
Default Gateway: 172.16.23.1
===========================================================================
Persistent Routes:
Network Address Netmask Gateway Address Metric
192.16.3.16 255.255.255.240 172.16.23.80 1
192.168.3.16 255.255.255.240 172.16.23.18 1
10.20.3.21 255.255.255.255 172.16.1.27 1
10.20.6.25 255.255.255.255 172.16.1.27 1
172.16.23.0 255.255.255.128 172.16.23.34 1

SERVER B
------------
Active Routes:
Network Destination Netmask Gateway Interface Metric
0.0.0.0 0.0.0.0 172.16.23.10 172.16.23.153 1
10.100.100.0 255.255.255.0 172.16.23.93 172.16.23.153 1
127.0.0.0 255.0.0.0 127.0.0.1 127.0.0.1 1
172.16.23.0 255.255.255.0 172.16.23.153 172.16.23.153 1
172.16.23.153 255.255.255.255 127.0.0.1 127.0.0.1 1
172.16.255.255 255.255.255.255 172.16.23.153 172.16.23.153 1
192.168.5.0 255.255.255.0 172.16.23.93 172.16.23.153 1
224.0.0.0 224.0.0.0 172.16.23.153 172.16.23.153 1
255.255.255.255 255.255.255.255 172.16.23.153 172.16.23.153 1
Default Gateway: 172.16.23.10
===========================================================================
Persistent Routes:
Network Address Netmask Gateway Address Metric
10.100.100.0 255.255.255.0 172.16.23.93 1
192.168.5.0 255.255.255.0 172.16.23.93 1

 

[Phillip Windell]

Well, these Servers are both in the same subnet if the mask is 255.255.255.0
and therefore there is no "routing". If you are using 255.255.255.128 then
"Server B" is in an unusable subnet unless it is split futher with another
mask. One of the two has an incorrect mask, since one is using
255.255.255.0 and the other is using 255.255.255.128.

Exactly how many routers are in your network? I'm counting at least 4
different "Gateways". Two of the "Gateways" for Server A are not valid
because they aren't in the same subnet as the server. A gateway must be in
the same subnet as the host using it,...otherwise how is it going to get to
the gateway if it needs a route and another gateway to get to the gateway?

SERVER A

172.16.23.0 255.255.255.128 172.16.23.34 172.16.23.34 1

Why is this one using this mask when the other Server is using
255.255.255.0? Server B would have to have at least 255.255.255.224 or
higher to work. Using 255.255.255.0 creates a conflict while using
255.255.255.128 would only put it in the last subnet which is "usable", so
it has to be 255.255.255.224 or higher to breakup the last (second) subnet.

Persistent Routes:
Network Address Netmask Gateway Address Metric
192.16.3.16 255.255.255.240 172.16.23.80 1
192.168.3.16 255.255.255.240 172.16.23.18 1

Are these real routers? What are they? (172.16.23.80, 172.16.23.18)

10.20.3.21 255.255.255.255 172.16.1.27 1
10.20.6.25 255.255.255.255 172.16.1.27 1

These are in the wrong subnet. They are invalid.


From a command line type "Route -f" to clear the tables and reboot. The
tables will rebuild based on the machine's network settings. Make sure
those network settings are right or you are wasting your time. Static
routes cannot be determined accuartely without having an accurate knowledge
of your topology.

 

[Ed Horley]

I would simply correct the subnet on whichever server needs it. I imagine
you intended to use a /24 or a 255.255.255.0 subnet. The problem is that
since the devices are most likely layer 2 adjacent the servers are trying to
arp for ip addressing info. In your configuration you have two different
broadcast addresses (same network address BTW). So, when a broadcast goes
out from server A which is using the /25 or 255.255.255.128 addressing you
are using the ip address 172.16.23.128 but on server B it is using a /24 so
it is using a broadcast address of 172.16.23.255. Server A will never be
listening for that address nor will server B be listening for the .128
address.
Your static routing issues are a different topic. Try correcting the subnet
and see if that works.

Regards,
Ed

 

[Guest]

Dear Philip

The servers are hosted at our ISP datacentre n the previous person who design the network topology has already left. I wasn't sure of the setup as the ISP has not been willing to provide more info. The 2 servers are previously in the same subnet mask which goes to ISP's load balancer which is subnet x.128. Now one server is in subnet zero because of the design of a flat network and it need to connect to my Load Balancer. I was told by my friend that the network design being done was lousy. Is it? This is because the whole range was not used and higher/lower range was assigned not in std. Ie. from the range of 0 to 128, some ip may have subnet 0 n some 128

I have 2 switches and 2 routers where it is connected to the isp. I can't change either server's subnet mask because the way the isp setup n connected. So, is there any other ways? Can I change the Server A to a higher range ip like 172.16.23.132 which is the same range as Server B but each having different subnet

The 192.x.x.x and 10.20.x.x that u see, if they are no longer exist in the network, will it still pose a problem to the network

U say Server B would have to have at least 255.255.255.224 or higher to work. Do u mean my Server B 172.16.23.153 subnet 255.255.255.0 has to be changed to 255.255.255.224

U r right, I'm wasting my time.

 

[Phillip Windell]

design of a flat network and it need to connect to my Load Balancer. I was told by my
friend that the network design being done was lousy. Is it?

Well it is certainly confusing anyway. I know I can't follow how it was
intended to work.

was not used and higher/lower range was assigned not in std. Ie. from the range of 0 to
128, some ip may have subnet 0 n some 128.

The 128 subnet won't work.
When splitting into subnets, the last subnet is always unusable. When you
split with a 128 mask you only get two subnets,...since the last one
(second) is unusable, you therefore only get one subnet out of it and have
simply "thrown away" the rest. To gain back any addresses from the second
subnet you have to keep splitting it with higher masks.

U say Server B would have to have at least 255.255.255.224 or higher to work. Do u
mean my Server B 172.16.23.153 subnet 255.255.255.0 has to be changed to
255.255.255.224?

Sorry, I should have said 255.255.255.192,...my mistake
On anything higher than 172.16.23.128,...yes,...at least until you hit
172.168.23.192, then you have to go to 255.255.255.224. You can keep
repeating the process unitl the final subnet only has 4 addresses (2 usable
host) then stop there. then you have only lost four addresses, but then you
have a bunch of subnets to deal with that you may not have the hardware to
be able to use. Subnetting is not fun and can be a bit complicated,...I'm
not even going to garuntee my own accuracy here being I did it off the top
of my head. This stuff shouldn't be attempted without careful planning.

U r right, I'm wasting my time.

Well I doubt I'll ever be able to understand and picture in my mind clearly
enough what is happening there to be of any help.