ISL to dot1q on ports

[ddemirchi]

Hi,

Is there a know issue or what version of IOS supports ISL on gig ports to dot1q on fast Ethernet ports.

Task:

Pass multiple VLANs for Cisco APs with 1031 and 1200 series.

Switches; 2950s, 3500s and 3550s

1. Currently switch configured with

switchA gig0/1 ISL, switchB gig0/2 ISL

- I am trying trunking the fa0/6 or any ports.

- APs configured properly to accept VLANs.

-- End result: Not working.

2. Currently switch configured with

switchA gig0/1 dot1q, switchB gig0/2 dot1q

- I am trying trunking the fa0/6.

- APs configured to properly with VLANs.

-- -- End result, working.

Has anyone experienced this issue and is there a work around for it?

Thanks for any inputs

Dean

[e-dennington]

What switch are the APs connected to? the 2950 the 3500 or the 3550?

2950 switches only support dot1q trunks.

[ddemirchi]

You are correct with 2950.

But, 90 % of switches 3500 and 3550 series which they are support ISL or dot1q.

When they were deployed left defualt configuration (ISL).

would it possible to configure isl between switches and dot1q on fastethernet ports?

[ankbhasi]

Hi Friend,

Yes it is possible to configure ISL between switches and dot1q on fastethernet ports.

But is there any specific reason why you want ISL to be working? Is there any problem using dot1q between switches which is working in your scenario.

Also when you have mentioned you are trunking fastethernet ports you are using which trunking protocol (isl or dot1q)?

Regards,

Ankur

[devang_etcom]

hi ankur,

how are you? after long time... nice to see you again in forum...

so here planning to use ISL and dot1q both in the same network... is there any benifit or advantage or some example for the same???

regards

Devang

[ddemirchi]

Hi,

You asked:

so here planning to use ISL and dot1q both in the same network... is there any benifit or advantage or some example for the same???

My experiences, stay away from ISL :-)

It is good for Cisco devices to Cisco.

ISL is Cisco propriety.

Market standard is dot1q. if you planning to use, connect non Cisco devices then use dot1q.

[ankbhasi]

Hi Devang,

Thanks for your warm welcome!!

As per my experience there is no benefit or advantage using ISL and Dot1q at a same time. If possible it is better to avoid ISL.

Regards,

Ankur

[ddemirchi]

Hi,

I really don't like to mixe ISL and dot1q in the network. However, the network already setup and it is in productions.

1. is there any specific reason why you want ISL to be working

Yes, my environment 7x24x365, lots of change control to Accomplish this task.

2. Is there any problem using dot1q between switches

No. This is a live environment. The switches already configured with default setting and it is ISL.

3. when you have mentioned you are trunking fastethernet ports you are using which trunking protocol (isl or dot1q)?

Cisco APs supports only dot1q, like catalyst 29xx series.

4. Yes it is possible to configure ISL between switches and dot1q on fastethernet ports.

What version of IOS?

Does this supported on Catalyst 35xx?

I already tested on 35xx and it doesn't support dot1q on fastethernet if switches configured ISL to communicate.

Remember, ISL and dot1q have different headers...

Thanks

[ankbhasi]

Hi Friend,

When you say "I already tested on 35xx and it doesn't support dot1q on fastethernet if switches configured ISL to communicate"

Can you please confirm what configuration your are applying to your fast etherenet ports when you configured ISL between switches?

DTP is not supported on the cat3500XL, so the trunk should be configured in the nonegotiate dot1q mode.

I understand ISL and dot1q use different headers but trunking is always point to point and only comes into action when frames passes through those ports so it really does not matter if one port is configured for ISL and other ports on same switch is configured for dot1q and it is better to avoid this situation but because in your case network is already configured I do not think there is any issue and it should work.

Regards,

Ankur

[ddemirchi]

Hi Ankur,

Here's my patial config:

==== doesn't work ====

Catalyst 35xx

int fa0/6 or any fa ports in these switch.

description AP-Test-dot1q

switchport trunk encapsulation dot1q

switchport mode trunk

switchport trunk native vlan 51

switchport trunk allowed vlan 1,51,53,55,1002-1005

Speed 100

Duplex full

no ip address

interface GigabitEthernet0/1

switchport trunk encapsulation isl

switchport mode trunk

no ip address

Thanks for any suggestions

[ankbhasi]

Hi Friend,

Can you update what does not work? Trunk does not come up ? If yes on the fastethernet?

Can you paste the output of "sh interface fa0/6 switchport" and "sh interface gig0/1 switchport"

Also is this 3550 switch or 3500XL switch?

Regards,

Ankur