Using Catalyst 2950 Blindly

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Oct 31st, 2007
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I hv a 2600 Router doing the intervlan routing and two 2950 Catalyst switches (A&B).My setup is to have switchA act as a bridge on its defaults settings connecting the router to switchB's Trunk port.When swichB is connected directly to the router,The vlans work ok till I include switchA btwn the two.Misin wat?

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the_chris Wed, 10/31/2007 - 12:29
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"This is not a reply just an addition"

To note further switchA is woking okay when untagged traffic is connected to it.I hav a problem with switching tagged traffic thro' it to the other switchB.What do I need to do to solve this?Pliz assist...

Kevin Dorrell Wed, 10/31/2007 - 12:45
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Also, do a show vlan and show vtp status on each switch to make sure they have the same set of VLANs.


But from what you say about tagged traffic, it could be a trunk issue. Do a show interface trunk on each side of the link connecting the two, and check they are trunking correctly.


Kevin Dorrell

Luxembourg


Jon Marshall Wed, 10/31/2007 - 12:30
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Hi


the port on switch A that connects to the router and the port on switch A that connects to switch B - are they both trunk ports as they will need to be.


Jon

the_chris Wed, 10/31/2007 - 13:21
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Thanks Kevin.Dorrel and Jon for your quick replies,


I tried to set both of the ports interconnecting the switches and the router but nothing changes.The funny thing is that if I replace the switchA with another vendor's smaller scale 4port switch the setup works perfectly.All I need from My cisco switchA is to transfer all traffic to switchB which handles the vlans.As I said earlier the switchA handles well untagged traffic the only issue is when the traffic is tagged.Waiting for your valued responses

scootertgm Wed, 10/31/2007 - 13:36
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They might be in different vlan domains. Make sure they have the same domain name. Then they will trade vlan information.

the_chris Wed, 10/31/2007 - 14:17
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Remember only switchB is to have the vlans and is communicating with the router.switchA is only bridging the router with the switchB - nothing else.

scootertgm Wed, 10/31/2007 - 14:50
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If switch A does not have the same vlans that switch B does, then it will not pass the vlan information. I literally had a similar problem when a new switch was installed at a site.


The new switch sat between the router than the rest of the lan. It was missing one vlan (lets say 100) Because of this, VLAN 100 could not talk to the router or anything outside the network.

the_chris Wed, 10/31/2007 - 19:21
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Please get my setup:switchA is not configured for anything.It is running on the factory defaults.(No vlans or vtp is setup on it)I purely want it to function like a bridge.


I want it to switch traffic from the router to switchB which is quite far away through the switchA but it appears to filter tagged traffic.Other small switches are working fine n I don get why the cisco cannot work blindly and transfer all traffic tagged or untagged.what is denying tagged traffic?


sample schema:


ROUTER --- SWITCHA(Default Settings)------ SWITCHB (VLANS Configured) ---- CLIENTS



the_chris Wed, 10/31/2007 - 19:32
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Please get my setup:switchA is not configured for anything.It is running on the factory defaults.(No vlans or vtp is setup on it)I purely want it to function like a bridge.


I want it to switch traffic from the router to switchB which is quite far away through the switchA but it appears to filter tagged traffic.Other small switches are working fine n I don get why the cisco cannot work blindly and transfer all traffic tagged or untagged.what is denying tagged traffic?


sample schema:


ROUTER --- SWITCHA(Default Settings)------ SWITCHB (VLANS Configured) ---- CLIENTS



Kevin Dorrell Wed, 10/31/2007 - 20:18
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Switch A will need to know about all he VLANs you want it to pass, otherwise it will only pass untagged traffic. It can find out about the VLANs either by you configuring them, or by learning them from VTP. Did you do show vtp status on each switch like I suggested?


Also, the link must be a trunk, otherwise it will not pass tagged traffic. Could you do show int trunk on each switch, and check it is trunking?


A small dumb switch may work OK because it passes anything transparently. But OTOH, you will not be able to assign its ports to VLANs.


Kevin Dorrell

Luxembourg


the_chris Wed, 10/31/2007 - 20:47
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Thanks Kevin ,


I get u now.So theres no way a cisco switch can pass tagged traffic transparently....

I dont think of using vtp for now incase the switchB will be replaced in the near future with another vendor's device not necessarily a switch.I will try add vlans manually on switchA,the trunks are already set.Hopefully am not supposed to configure the vlans per port.I planned not to configure SwitchA for any vlans thats why I thought a transparent switch would really carry the day.Any further advice on adding the vlans?

Kevin Dorrell Thu, 11/01/2007 - 03:05
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Personally, I would just enable VTP on Switch A and let it catch up. The VLANs will be automaticaly added to the trunk.


In fact, if Switch A has never had VTP, and Switch B is VTP server, and no VTP password, then just making the link into a trunk (at both ends) should automagically enable VTP and synchonise all its VLANs.


Kevin Dorrell

Luxembourg

the_chris Thu, 11/01/2007 - 11:17
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Thanks again Kevin,

Had quite a busy day I couldn't respond earlier.Allow me bug you further and anyone else willing to assist me.


As I said earlier I will be changing the switchB to another vendor's Wireless Access Point with capability to support vlans using 802.1q encapsulation which is the main reason why am hesitant to implementing VTP.I have a test setup of this and the same is not working.


Sample schema II:

Router(Cisco-2600)-- SwitchA(Cisco-2950) --- Wireless AP -- Clients


Breakdown:

The router will be doing the intervlan routing between it and the AP.As earlier the switchA is to remain on default settings and switch traffic to the AP(No vlans are to be served from this switchA but from the AP).Remember the AP is capable of handling vlans thus basically the link between the Router and the AP should be the trunk;the issue here being the SwitchA joining the two.

Note that with the AP connected directly to the Router the Clients on vlans in the AP are working perfectly which fails when I introduce the switchA.This makes me feel am missing something on the switch's configuration if not anything else.


Please give your valued thoughts and recommendations on this new setup.




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