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Layer 3 Module Configuration

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by deming schools network 2 views

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I am attempting to configure a 3Com 3300 Switch with a Layer 3 Module installed in order to provide some network traffic management. Want to setup VLANs and change IP Subnets in the process. All subnets will be setup using the 10.0.0.0 network with subnet 255.255.255.0. (must leave current IP subnet 192.168.0.0 in place for main office temporarily) The equipment setup is as follows for my testing environment.

3300 Switch w/module installed
Connected to current network via cross connect patch cable
Connected to Layer 2, 3300 Switch via cross connect on port 6
Static IP: 192.168.0.7
Mask: 255.255.255.0
Gateway: 192.168.0.1
VLANs configured:
VLAN1 (default) all ports belong except port 6
VLAN2 (index 2) port 6 (no tagging)Layer 3 Module
Static IP: 192.168.0.8
Mask: 255.255.255.0
Gateway: 192.168.0.1
VLANs Configured
AN Index VLAN ID Name
1 1 Default VLAN
2 2 VLAN 2

IP Interface configuration
Index Type IP Address Subnet Mask State VLAN Index
Index Type Address subnet mask state Vlan index
1 VLAN 192.168.0.8 255.255.255.0 Up 1
2 VLAN 10.0.9.1 255.255.255.0 Up 2

RIP enabled, IP Routing Table shows default +:
Destination Subnet Mask Metric Gateway Status
10.0.9.0 255.255.255.0 -- -- Direct
10.0.9.1 255.255.255.255 -- -- Local
192.168.0.0 255.255.255.0 -- -- Direct
192.168.0.8 255.255.255.255 -- -- Local

Layer 2 3300 Switch
Connected Layer 3 switch via cross connect patch cable on port 1
Static IP: 10.0.9.2
Mask: 255.255.255.0Gateway: 10.0.9.1

VLANs configured:
VLAN1 (default) all ports belong except port 1
VLAN2 (index 2) port 1 (802.1Q tagging)

For some unknown reason, this configuration worked for about 10 minutes. I was able to ping both 10.0.9.1 and 10.0.9.2 from a machine connected to the current network. Then it quit working? and I can?t seem to figure out why. Anyone with experience in configuring layer 3 please comment!

3 replies

by Former member

Hmmm. First thing to mind is that trunking on the 10.0.9.2 L2 switch is not necessary since you have no VLANs to pass or broadcast (it is the default VLAN1 configuration) so no trunking is necessary. Remove the trunking configuration from port 1 andtry again. If you had two bonifide VLANs on this L2 switch, where two or more workstations belong to two or more different VLANs, then you would setup a trunk port, belonging to no VLAN, and use the L3 switch to route between them.

Remember that the L2 switch is not performing and multiple VLAN configurations nor any VLAN routing, so attach it as you would any other switch. The IP configuration on the L2 switch is not really relevent only for telnet purposes...But any station attached to theL2 switch I guess could be of the 10.0 network and will pass through the L2 switch, essentially because it is not concerned with the IP (L3( address) as long as the station's Default gateway is pointing to the L3 switch, which is where the routing will occur.

Thirdly, I don't believe a Trunking port should belong to any VLAN, since it is broadcasting ALL VLANs.

Finally, I beginning to see where you're going with this, but it was confusing. Your first L3 VLAN1 has a subnet of 192.168..., your second VLAN1 (L2 switch) is 10.0.9.0, so if you're attempting to connect both VLAN1's it won't work since they're on different subnets. If you want a common VLAN spanning both switches, do not use the default VLAN, create VLAN 100 and give it a subnet of 10.0.9.0 then create it on the L2 switch and use a trunk port. The trunk port will be a member of ALL VLANs. All Trunk ports must also use the same tagging and VTP protocols (802.1q in your case).

by deming schools network

I had to read this response several times before I figured it out... I guess we were confusing each other :-)

Your last paragraph was essentially correct, and explains how I have these two (test) VLANs configured. The problem I was having wasin the local (192.168.....) router.. the router on this subnet had to have a static route entered that pointed it back to the layer 3 module... once that was done, WAHLA! total communication.

Thanks for your time.. I know this one was hard to answer, because it was hard to ask!

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