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Cisco Catalyst Switch Split

Posted on 2011-09-13
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Last Modified: 2012-06-27
I need to take a 24-port Catalyst switch and basically carve it up into four distinct six-port switches. Each "switch" needs to be completely isolated from the other "switches". I assume VLANs would be required here, however the traffic needs to be free of any VLAN tagging, as it's connected to ISP equipment. These VLANs only need to exist on this one switch. How can this be done so there is no tagging whatsoever?

The longer story (though not completely required) is that we have three ISPs in our office and a redundant pair of Internet routers. Since the ISP equipment only has one port each, this Catalyst switch would split the ISP traffic to each router, as only one will be active at a time, using each of the first three VLANs. Then the LAN traffic from the routers would use the fourth "switch" VLAN to combine links before hitting the office LAN. Image attached.

Thanks!
VLANs.png
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Question by:MacGyverSolutions
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Expert Comment

by:Soulja
ID: 36530724
I don't know if I completely understand your requirements, but you should just be able to create the vlans, assigned the ports with switch port access vlan x, switchport mode access. As long as you don't create any trunks there will be no tagging.
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Expert Comment

by:Craig Beck
ID: 36531128
Soulja has explained exactly what you need...

This code will put ports 1-6 in VLAN1, 7-12 in VLAN2, 13-18 in VLAN3 and 19-24 in VLAN4...

conf t
vlan 2
exit
vlan 3
exit
vlan 4
exit
int range gi0/1 - 6
 switchport mode access
int range gi0/7-12
 switchport mode access
 switchport access vlan 2
int range gi0/13 - 18
 switchport mode access
 switchport access vlan 3
int range gi0/19 - 24
 switchport mode access
 switchport access vlan 4
end
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Author Comment

by:MacGyverSolutions
ID: 36532373
I will try this out soon and let you know, thanks! If I don't specify a VLAN on the first range (1-6), is VLAN 1 assumed, and I will stop getting these native VLAN mismatch errors?
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Expert Comment

by:Soulja
ID: 36532404
Native vlan mismatch errors? You should not be getting those unless you have trunks configured with mismatch native vlans or have mismatched access ports plugged into each other. Since you are not using trunks I assume the latter.
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LVL 45

Expert Comment

by:Craig Beck
ID: 36532677
As Soulja says, you will only get native VLAN mismatch errors if trunks are configured.

If you don't set a VLAN on the first range VLAN1 is assumed by default.
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Author Comment

by:MacGyverSolutions
ID: 36552508
There was still some weirdness after this change because I was getting "Received 802.1Q BPDU on non trunk FastEthernet0/13 VLAN4" and "Blocking FastEthernet0/13 on VLAN0004. Inconsistent port type" but apparently switching to RPVST fixed this up. Perhaps the ISP was sending their own BPDU packets?

The configuration DOES seem to be working, however the port connected to one of the WAN ports is blinking green/orange back and forth, with short spurts of what appears to be regular activity every minute or so. Anyone know what this pattern means?
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Accepted Solution

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MacGyverSolutions earned 0 total points
ID: 37153965
Ended up resolving this by setting up four individual private VLANs, which do not use spanning-tree, trunks, etc. Appears to be working well.
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Author Closing Comment

by:MacGyverSolutions
ID: 37175726
Had to use a more customized configuration than I wanted, but it works now. Whoever replaces me someday may not have a clue on how this configuration works.
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