Can’t ping servers in our school division after adding cisco 891 routers

175 pts.
Cisco Routers
Network Configuration
I am currently moving our school network from a flat network to a routed network. There used to be only one DHCP server at the central office that was handing out IP addresses for the entire school division network. The IP range was 172.16.x.x. A router is being added at each site and each site will have to have it's own DHCP server that will hand out IP addresses for their school only (using the 10.194.x.x) address scheme. There is one division wide domain (with each school in the division having a secondary server in the domain and the main domain controller is at the central office location). Each school also has a separate lab domain where only one server makes up the domain. Previous to adding a Cisco 891 router to segment the first school, I could ping all of the school divisions servers (whether they were part of the main division domain or the separate lab domains that each school has). However, after implementing this first router at one school, i can no longer ping this schools lab server from any other school or our central office. I also can't ping the schools admin server that is part of the school division wide domain from out side this school. I can ping the lab server and admin server at this school by IP address, but not by the server name. What do I need to change to allow me to be able to ping all servers in the school division like I used to do now that it is becoming a routed network and not just a flat network? I know in the past that I could ping the lab servers because Netbios was allowing for the servers to be found. Can DNS running on the central office server handle both 172.16.x.x addresses as well as the 10.194.x.x IP addresses together? If I right click the domain on the DNS server at central office and choose properties and then select the name servers tab, the Holy Cross server (the school that has the Cisco router installed and had it’s IP scheme changed) shows unknown for the IP address of this server. After I put it back in I can ping this schools admin server. However, after about 15 minutes DNS will lose the IP address again and shown Unknown again. Any help would be greatly appreciated.

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Do you have WINS set up properly? In a full/complete AD setup, you may not need it, but by having a central WINS server set up, and all servers and workstations referencing it (through the DHCP properties) you can provide name resolution, at least for Window protocols.

Formerly, in your flat network, one of your servers probably WAS acting as a WINS server, as everything was reachable via broadcast messages. However, by routing, this method doesn’t work like it did without a little “help” to cross the broadcast domains. Registering with a consistent server for servers AND workstations will then allow name resolution.


Sounds to me that you dont have inter-VLAN routing set up properly. If your ENTIRE network uses the 172.16.x.x, and you throw in the 10.-w/e, the router needs to know it needs ot translate / route between the 2 subnets.

You could use either static routing from each site to the “main” network, as that would require so few statements, or your could enable a smaller dynamic routing protocol like RIPv2 to allow traffic to flow from the 172.16.x.x to the 10.x.x.x and vice versa…

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  • petkoa
    Most probably the reason to be unable to ping machines across local private adressed LANs is that private IP chunks are not routable - and cisco router knows this. So, you'd have to explicitly configure routes to these LANs on your routers (static or according to the protocol they use to communicate).
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  • Featured Member: Snapper70 - ITKE Community Blog
    [...] Can’t ping servers in our school division after adding Cisco 891 routers [...]
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  • ShawnHendricks
    As Petkoa's post suggests, 10.x.x.x IP addresses are private and non-routable. You must explicitly state the route and apply it to the appropriate router interfaces in order to make private addresses routable. See Have you run a traceroute to see where your ICMP (Internet Control Message Protocol) packets are lost?
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