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I have two sub nets on Cisco packet tracer, the central node(switch) that networks all nodes in sub net A is connected to a router which connects to switch B which is the central node for sub net B.

SWITCH A{connected to a bunch of ---->Router<----------SWITCH B{connects a bunch of computers}
 computers}

The nodes in sub net A are communicating well and also all the nodes in sub net B, my problem is to configure the router to forward packets from switch A to switch B and vice versa? How to achieve is this such that pinging host in B from host in A is what i desire to learn or discover, Thanks for your help

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  • Routers automatically route by default between directly connected networks that are configured on the router.
    – Ron Maupin
    May 8 at 20:25
  • Then why does a ping fail when i try to ping a host in sub net B
    – CodeTiger
    May 9 at 6:49
  • Because you did not have the networks configured on the router. Notice that I wrote, "Routers automatically route by default between directly connected networks that are configured on the router."
    – Ron Maupin
    May 9 at 12:03
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As a minimum you have to configure:

  • a shared IP subnet for all devices connected to switch A, e.g. 192.168.0.0/24
  • a shared IP subnet for all devices connected to switch B, e.g. 192.168.1.0/24
  • the router is connected to both switches and requires an address in each subnet, e.g. 192.168.0.1 & 192.168.1.1
  • the hosts in each subnet need to use the router address on their side as gateway for the remote subnet, either via the default route 0.0.0.0/0 ⇒ 192.168.0.1 resp. 0.0.0.0/0 ⇒ 192.168.1.1, or by a specific route, e.g. 192.168.1.0/24 ⇒ 192.168.0.1 and vice versa.
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  • I have one question though, if i configure a different gateway address for router interface 0/1{fastethernet} from the gateway address i configured on interface 0/0{fast ethernet}, why does communication between the two sub nets?
    – CodeTiger
    May 9 at 7:06
  • Configure a different gateway address where? On the router? The hosts? What happens? What were you expecting?
    – Zac67
    May 9 at 7:14
  • I configured 10.0.0.1 for router interface for fast ethernet 0/0 and then 192.168.90.1 for router interface fast ethernet 0/1.... The computers are communicating thanks
    – CodeTiger
    May 9 at 7:24
  • So how does a different gateway address on router inteface 0/0 let me communicate with devices whose default gateway address are using router interface address at 0/1?
    – CodeTiger
    May 9 at 7:28
  • Different gateway address from what? A gateway is a router that provides connectivity to other networks. Hosts only need to know where a gateway leads to (the route prefix) and its address within the local network that they need to pass packets to. The router then forwards these packets according to its own routing table.
    – Zac67
    May 9 at 7:36
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The router will have an interface on each switch. The IP address will be in the subnet associated with each switch.

Your devices’ gateway address will be the router interface address.

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  • Okay trying that in a moment
    – CodeTiger
    May 9 at 6:53

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