expansion of subnet created network problems

visteknetworking · ‎05-17-2010

Hi,

We have been expended our subnet from 192.168.0.0/24 to 192.168.0.0/21.

We can ping some stations others do not respond to ping.

Ip configuration is the same on all printers we have been testing.

Z:\>ping 192.168.1.100

Pinging 192.168.1.100 with 32 bytes of data:

Reply from 192.168.1.100: bytes=32 time=1ms TTL=255
Reply from 192.168.1.100: bytes=32 time=1ms TTL=255

Z:\>ping 192.168.1.102

Pinging 192.168.1.102 with 32 bytes of data:

Reply from 192.168.1.102: bytes=32 time=3ms TTL=64
Reply from 192.168.1.102: bytes=32 time=4ms TTL=64

Z:\>ping 192.168.1.104

Pinging 192.168.1.104 with 32 bytes of data:

Reply from 172.20.1.226: TTL expired in transit.
Reply from 172.20.1.226: TTL expired in transit.
Reply from 172.20.1.226: TTL expired in transit.

I am really lost on this. Please let me know what kind of info you want me to post I can make it happen. If you dealt with same situation please help me out

I know that some say that has to be some"user error" but all these three printers have same subnet and default gateway

Thanks in advanced

Jon Marshall · ‎05-17-2010

Can you post -

Host Z - IP address/subnet mask

all 3 printers - IP address/subnet mask

Jon

Giuseppe Larosa · ‎05-17-2010

Hello,

first of all: are you using DHCP or each end user device is manually configured?

in second case all end user devices have to be tuned to update the new subnet mask.

this is because all devices have to agree on the directed broadcast that depends from subnets mask ( it is defined as all 1s in the host portion)

you should have added some new vlans with other /24 IP subnets associated to each of them. In this way you would have left untouched existing device

a /21 subnet is near to be too big (too many broadcasts)

if your environment has managed switches consider the use of multiple vlans

we see that first device answers with TTL=255 meaning it is on wire, second device uses 64 and should be a different settings, the answer for third ip address comes from another subnet.

Reply from 172.20.1.226: TTL expired in transit.

this may mean that there is a routing loop somewhere in the network.

Hope to help

Giuseppe

visteknetworking · ‎05-18-2010

HI Giuslar,

thank you very much for your detailed reply.

Can you please give me some more details about this line

/21 subnet is near to be too big (too many broadcasts)

i have about 5 cisco switches all ports are being used.

All servers have static ip's with /21 bit subnet , clients with dhcp for the meant time/24 bit subnet because we started to have all these network issues.

What is the best course of action would be for me at this point of time.

the network setup is flat , i.e we don't use vlans right now

Thanks again

Giuseppe Larosa · ‎05-18-2010

Hello Vistek,

>> i have about 5 cisco switches all ports are being used.

what type of switches have you got? if any is a multilayer capable moving to multiple vlans would be easy

using 8 /24 IP subnets mapped to 8 different vlans should provide you a better network

Hope to help

Giuseppe

visteknetworking · ‎05-18-2010

so in this case the best way is to split network into 8 subne

ts each with 24 bit, correct?

the way how our switches setup is a start so one main switch 48 ports 1GB which servers all the servers and all other switches connected to it too.

Should I create vlans on that main switch and then each switch which plugs into will be setup witch different subnet is this how shoud i do it ?

I am not big expert on vlans, do I create vlans on my main switch

Thanks

Giuseppe Larosa · ‎05-18-2010

Hello Vistek,

you can have 8 vlans deployed in all switches if needed

all devices must agree on the existance of these vlans in order to use them correctly.

This can be achieved by:

a) using VTP protocol with main switch and another switch in VTP server mode

b) or by using VTP mode transparent in all devices this requires configuration of the 8 vlans in each switch

Hope to help

Giuseppe