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Simple VLAN configuration "gotcha's"

I have a C4006, NmpSW 7.4[3], currently it has one VLAN - VLAN1, with a "set int sc0 1 172.16.0.9/255.255.0.0".

I want to split the X4448 in slot 6 into a second VLAN, VLAN 10, to "share" some Gigabit copper ports with a second switch - a C5000, its VLAN 1.

The C5000, NmpSW 6.3[3] has 3 VLANS, VLAN 1, 2 & 3, with connections from these VLANs to a 4000 router and has "set int sc0 1 192.168.8.40 255.255.255.0". It has a X4428-GB-RJ45 module, h/w ver 1.5 in slot 3.

I believe I should be able to add a second VLAN to the C4006, call it VLAN 10, allocate it 6/33 - 48. Take a cross-over cable from port 6/33 to the C5000's slot 3/1 port.

I've tried this on a test system and I note that on power up the C4006 issues an error message "native VLAN mismatch detected on port 6/33". When I do a "sh cdp nei" I note there is an asterisk next to the Port ID 3/1 for the C5000 connection port.

Is what I've proposed "safe" and what if any "gotcha's" are there

5 REPLIES
Bronze

Re: Simple VLAN configuration "gotcha's"

Essentially what you have done is bridge vlan 1 on the cat5k with vlan 10 on the cat4k.

If this is your intention then there is nothing wrong with that.

To stop the "CDP native vlan mismatch" message just disable cdp on that port using the "set cdp disable" command. The only reason that message is showing is because the cat4k is sending CDP messages saying that its port belongs to vlan 10 and the cat5k is sending CDP messages saying its port belongs to vlan 1.

Re: Simple VLAN configuration "gotcha's"

Hi,

another possibilities:

a) set logging level cdp 3 default

- only CDP lever 3,2,1 messages will be sent to syslog

b) set cdp version v1

CDP version 1 doesn't send native VLAN info

Regards,

Milan

New Member

Re: Simple VLAN configuration "gotcha's"

My intention, as you rightly point out, is to bridge the two VLANs. My uncertainty was more in regards to how the Cisco OS was going to behave when real traffic starts flowing.

When the traffic does start flowing I intend monitoring the flow rate and probably use Gigabit EtheChannel to provide the appropriate path dimension.

Do you have an opinion on this latter aspect?

Re: Simple VLAN configuration "gotcha's"

Hi,

the Configuration Guide (http://www.cisco.com/univercd/cc/td/doc/product/lan/cat4000/rel7_1/config/channel.pdf) examples are always showing the same VLAN on both EtherChannel sides.

But I'd try to test your configuration in channel mode ON.

I think when all ports are in VLANx on one switch and all ports are in VLANy on the other switch, ports in on mode do not exchange PAgP packets and the EtherChannel should work. If not, I'd try to disable CDP on the ports involved.

Regards,

Milan

New Member

Re: Simple VLAN configuration "gotcha's"

Bridging the two systems in "real life", with a single cross over cable, is proving more difficult than anticipated.

On the switch#9 [4006 NmpSW 7.4(3)] that is sharing its gigabit Ethernet module [ws-x4448-gb-rj45 hw:1.0] using VALN 10, I get a status - Inactive on the "bridge port".

On the switch#1 [4006 NmpSW 6.3(3)] requiring the "bridged" module access I get a status "not connect" on the port on the module [ws-x4424-gb-rj45].

I’ve tried doing a module reset on switch#9’s module 6 to avail, I’ve also tried disabling and re-enabling the bridge ports at each end also to avail.

Any suggestions?

My test system a 4003 with a section of one of its modules VLAN’d [10] successfully bridges to a 2950.

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