Lan routing

Answered Question
Oct 17th, 2008

I have a PC that's on the 10.30.46.199 network that's passing data to a PC on the 10.35.44.3 network.

I attached a drawing that shows the traffic direction.

The routing is done on the 2801 (our core RTR).

Is there a way I can get the traffic to stay in the Cisco 3750?

In other words, since both PCs are on the Cisco 3750, can't the traffic from PC #1 destined to PC #2 go to the Cisco 3750 and then routed to the switch port that PC #2 is on?

Any thoughts or suggestions?

Thanks, Gary

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Correct Answer by Joseph W. Doherty about 8 years 1 month ago

The other posters have already described how to enable routing on the 3750 and that you likely will need to change the gateway for the subnets connected to the 3750.

Assuming the 2801 was only being used for LAN routing, you'll likely should see a speed improvement for large data transfers between the two directly connected networks and will no longer need the 2801. However, if there's other routing that was being conducted via the 2801 (e.g WAN routing), just enabling routing on the 3750 may break communication between the 3750 and 2801 unless other measures are implemented.

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Jon Marshall Fri, 10/17/2008 - 13:58

Gary

I can't open visio as i have don't have it on my home laptop.

Assuming 10.30.46.199 is in a different subnet than 10.35.44.3 (and that's not definite without seeing the subnet masks), then yes you could do this on the 3750. The 3750 is a L3 switch and can do inter-vlan routing so you would have to L3 vlan interfaces on the 3750 for both vlans.

Jon

garyrivers Fri, 10/17/2008 - 14:10

yes, they are on different VLANs.

true the SW is L3 so that's what I was thinking. what do I have to turn on to get the inter-VLAN routing?

Thanks

Jon Marshall Fri, 10/17/2008 - 14:21

As an example

vlan 10 = 192.168.5.0/24

vlan 20 = 192.168.6.0/24

Assuming that the vlans have been created at L2 ie. a "sh vlan" on the 3750 switch shows both vlan 10 and 20

3750(config)# ip routing

3750(config)# int vlan 10

3750(config-if)# ip address 192.168.5.1 255.255.255.0

3750(config)# int vlan 20

3750(config-if)# ip address 192.168.6.1 255.255.255.0

That's it really :)

Jon

mattcalderon Fri, 10/17/2008 - 14:21

You would have to put an ip address on the L3 interface on the switch.

Example

interface vlan 1

ip add 10.35.44.x

interface vlan 2

ip add 10.30.46.x

ip routing

The thing though you would have to do is change the default gateway of the pcs to the ip address of the new interface vlans that you have created.

Correct Answer
Joseph W. Doherty Fri, 10/17/2008 - 15:42

The other posters have already described how to enable routing on the 3750 and that you likely will need to change the gateway for the subnets connected to the 3750.

Assuming the 2801 was only being used for LAN routing, you'll likely should see a speed improvement for large data transfers between the two directly connected networks and will no longer need the 2801. However, if there's other routing that was being conducted via the 2801 (e.g WAN routing), just enabling routing on the 3750 may break communication between the 3750 and 2801 unless other measures are implemented.

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