subnetting - Page 2 - Developer IT

What is the point of connecting two routers directly together

- by rubixibuc

The way subnets work, wouldn't connecting two router interfaces together require their own subnet between them. Unless that subnet mask has 31 bits, wouldn't that was adress space. I'm asking because I often seen that done in networking books. How can this be done without wasting IP Addresses? They usually draw this when explaining subnetting. They have a central router connected to several other each one supposed to be creating their own subnet. Is this really how subnettimg is done? Example <-------[Router 1]-----Wasteful Subnet-------[Router 2]------> | | | \/

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design a large scale network for an organization

- by Essam

hello.i am so new to networking i want to design a large scale network for an organization with HQ and two branches. i want to use class A address for that.my questions are: if i am using the network address 30.0.0.0 for the whole organization how can it be different from another organization company or whatever which is using the same address in another country? now i have the three locations for this organization,so i need 5 subnets [one for the HQ,two for branch A and branch B , one for connecting A to HQ and one for connecting branch B with HQ since i will use central DHCP server at the HQ,is that(number of subnetting) right? is it advisable to use class A or class B for this organization it term of address that will be wasted (lets say it is a university with two branches in two different states)?! that is all your help is highly appropriated.

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Cisco: Site-to-site VPN with cisco 878 and ASA weirdness

- by cpf

I currently have 2 sites, both connected to each other through 2 firewalls / routers in a site-to-site VPN. Pinging from server to server (Using 2mb/2mb SDSL) through that VPN obviously works, however, at one site, we have another internet connection (7m/400k ADSL), and only the link between the two sites should be on the other connection. All pc's should go over the other connection for internet, just communication between servers & Communication between pc's and the server at the other side should go through there too. What is configured at the moment is the server is using the SDSL directly as default gateway. Since it's not intended to surf anything it is a safe config. PC's are configured on the ADSL as default gateway. Now I wanted to route through everything that uses the range used on the other site, it should be sent from the ADSL modem to the SDSL modem, which has the VPN connection. I figured I could use OSPF to do so, however, OSPF doesn't seem to "detect" the range of the external site. Also (due to bad ip subnetting thanks to the other administrator), the ip used internally as the server on the other site also exists on the internet (causing a lot of confusion), so rdp-ing from our server to the server of the other site works (somehow), but tracerouting on the SDSL router (which should actually, in my opinion, go over the VPN) actually goes all over the internet. My question(s): Why doesn't the SDSL router ping the external ip through VPN, but the server does? Why can't I route from the ADSL router to the SDSL over VPN? I would seriously appreciate some help, since I can't figure out why it does it like this.

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Can I subnet a subnet?

- by Portman

Apologies in advance for the botched terminology. I have read the Server Fault Subnet Wiki but this is more of an ISP question. I currently have a /27 block of public IPs. I use give my router the first address in this pool and then use 1-to-1 NAT for all the servers behind the firewall, so that they each get their own public IP. The router/firewall is currently using (actual addresses removed to protect the guilty): IP Address: XXX.XXX.XXX.164 Subnet mask: 255.255.255.224 Gateway: XXX.XXX.XXX.161 What I would like to do is break out my subnet into two separate /28 subnets. And do this in a way that is transparent to the ISP (i.e., they see me as continuing to operate a single /27). Currently, my topology looks like: ISP | [Router/Firewall] | [Managed Ethernet Switch] / \ \ [Server1] [Server2] [Server3] (etc) Instead, I would like it to look like: ISP | [Switch] / \ [Router1] [Router2] | | | | [S1] [S2] [S3] [S4] (etc) As you can see, this would partition me into two separate networks. I'm struggling with what the correct IP settings would be on Router1 and Router2. Here's what I have right now: Router1 Router2 IP Address: XXX.XXX.XXX.164 XXX.XXX.XXX.180 Subnet mask: 255.255.255.240 255.255.255.240 Gateway: XXX.XXX.XXX.161 XXX.XXX.XXX.161 Note that normally you would expect Router2 to have a gateway of .177, but I'm trying to get them both to use the gateway originally given to me by the ISP. Is subnetting like this in fact possible, or am I completely botching the most basic concepts?

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how does a computer know which IP address will route information to the internet? [closed]

- by JohnMerlino

Possible Duplicate: How does IPv4 Subnetting Work? For example, I have a computer with a Network Inteface Card (NIC) which is an Ethernet card that is connected by Ethernet cables to a router. There is also another computer with a cable that is connected in another port of the router. This is a Belkin router operating over an Ethernet in the LAN. When I connect to serverfault.com, it maps to an IP address. My computer now has a task of connecting to that IP address. But my computer itself cannot connect to the serverfault IP address. Only the router can. So the task of my computer is to find the IP address associated with the node that will do the routing to the public internet. How does my computer know that a particular IP address in the local network belongs to the router, and is not another computer connected to the network? Is this information configured manually in the operating system itself? Somehow my computer must know that it must send ethernet frames to the router with the expectation that the router will then send the packet to a public IP. How does it know to send it to the router? Is the router's ip address stored in my computer like a key/value pair e.g. "router"="192.168.2.6", so that when I put a public ip address, my computer first knows to connect to 192.168.2.6?

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