Splitting Network On a VLAN

da.carlo 19 years ago

Hello,

I have a VLAN (145) with two networks configured on it. I am trying to split the network across two VLANs.

What I have done is create a second VLAN 805, create a interface vlan and add the IP address of the second network.

The equipment is a C6506 and C3750G. I have a port on the C6506 as switchport access vlan 805 and one on the C3750G as switchport access vlan 145. I used a crossover cable to connect the ports together. The C6506 is linked to the C3750G via a trunk with both V145 and V805 as allowed vlans on the trunk.

By connecting the two VLAN's I am combining the broadcast domains. I should be able to see devices on the same network (IP range) regardless of which VLAN they are connected to. The problem is I can not see devices on VLAN 145 from VLAN 805 and vice versa (same IP range).

Any ideas on what might be wrong?

Thank you.

Carlo

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linguafr 19 years ago

access switchports are for end users, i.e. hosts
the uplink between the two switches should be a trunk port with both vlans allowed - if you don't specify they're all allowed
you need to have a layer 3 interface for each vlan which will be the default gateways for the respective vlans. you can use a vlan int on the switches or another routing device as the default gateways.

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da.carlo 19 years ago

I think what I am trying to do is not clear.

I have one VLAN with two networks configured VLAN 145 10.0.0.0/23 and

192.168.55.0/23

I am trying to seperate the networks into two seperate VLANs.

VLAN 145 10.0.0.0/23 VLAN 805 192.168.55.0/23

Instead of of having to go out and change 80+ devices at one time I am creating the new vlan 805 adding the vlan interface address of

192.168.55.1/23 and removing it form vlan 145. Then using a cross connect between one switchport on vlan 145 and one on vlan 805 I am connecting the two vlans. This should allow devices on vlan 145 in the address range of 192.168.55.0/23 to connect to the routed interface vlan 192.168.55.1 configured on vlan 805.

Trunking the link keeps the vlans seperate. Cisco VLANs also maintain a seprate mac-address table for each VLAN. There shouldn't be a problem here either.

Switchport access vlans are untagged therefore traffic from vlan 145 should mix with vlan 805. Broadcasts should propogate and traffic should pass unhindered. Both ports should work as a switch port. Learn mac-addresses on either side and send traffic when appropriate.

Both Cisco's are running IOS. The 6506 has Version 12.2(18)SXE5 and the 3750 has Version 12.2(25r)SEB1.

Perhaps something proprietary with Cisco IOS is causing the problem?

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