Routing problem

[bijan.kianifard]

Hi All,

I have 2 questions:

1.I've configured the following routes on my router:

ip route 196.38.151.0 255.255.255.0 192.168.100.3

ip route 192.168.100.0 255.255.254.0

GigabitEthernet1/0

GigabitEthernet1/0 has 2 IP addresses 192.168.100.1 and 192.168.101.1 with the subnet 255.255.255.0.

Now I would like to enable FastEthernet0/0 with the IP address 192.168.100.4/24,but when I try to enable this interface I receive an error message indicating FastEthernet0/0 overlapped with GigabitEthernet1/0 and interface remained shutdown.What is the reason and how can I troubleshoot it?

2.After enabling f0/0 is the following route enough to forward traffic headed to 192.168.100.3/24 through f0/0 and not GigabitEthernet1/0?

ip route 192.168.100.3 255.255.255.255 f0/0

Thanks in anticipation

Bijan

[thisisshanky]

First of all, a router cannot share address from same subnet on any two interface..So you cannot assign 100.4 on fa0/0 as it overlaps with the subnet assigned to Gi 1/0.

I am notsure what you trying to achieve here.

Router--gi0/0-- ??

--------fa0/0-- ??

What is 192.168.100.3 ? If that is a router, which port of this router is it connected to ? Or are these routers connected via a switch ?

[bijan.kianifard]

Thank you very much

Let me describe the configuration:

As you observed I have a router with one Gi and one fa interfaces.This router now is connected to a switch through its gi interface.switch is connected to a hub and the other router with address of 192.168.100.3/24 is connected to this hub.I want to disconnect the switch from the hub and connect my router to this hub through f0/0.Therfore I have to change the route for traffic destined to 192.168.100.3. Now can you help me please?

[thisisshanky]

Disconnect hub and switch (cross cable)

Connect a straigh through from fa0/0 of R1 to hub. R1 still can retain the gig connection to switch.

Gig 1/0 should be re-iped to 192.168.101.1 (primary)

fa0/0 should be re-iped to 192.168.100.1 (primary)

fa0/0 goes to hub

gig 1/0 goes to switch.

No connection between hub and switch.

There is no need for the static route,

ip route 192.168.100.0 255.255.254.0 gig 1/0

Just keep the route,

ip route 196.38.151.0 255.255.255.0 192.168.100.3

[dgahm · Accepted solution]

The subnet 192.168.100.0 255.255.255.0 covers addresses from 192.168.100.0 through 192.168.100.255. So this is the same subnet that you trying to apply to F0/0. A router cannot have multiple interfaces on the same subnet.

The address 192.168.100.1 or 192.168.100.4 is just the address the router itself uses.

[milan.kulik]

Hi,

just one note to your routing commands:

"The practical implication of configuring "ip route 0.0.0.0 0.0.0.0 Ethernet 1/2" is that the router will consider all of the destinations that the router does not know how to reach through some other route as directly connected to Ethernet 1/2. So the router will send an ARP request for each host for which it receives packets on this network segment. This configuration can cause high processor utilization and a very large ARP cache (along with attendant memory allocation failures). Configuring a default route or other static route that directs the router to forward packets for a large range of destinations to a connected broadcast network segment can cause your router to reload."

See http://www.cisco.com/univercd/cc/td/doc/product/software/ios123/123cgcr/iprrp_r/ip2_i1g.htm#wp1040624

Regards,

Milan