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VLAN;How can I connect to this pre-configured IP?

Folks, imagine I have a 3750 in production. spanningtree-mode is pvst.

Ports fa1/0/1-fa/0/47 are assigned to Vlan 30. I see a SVI for VLan 30, IP=10.200.1.1/24. Vlan 30 interface is up/up.

vlan 1 is down/down.

Then on port fa1/0/48 on the 3750, I need to connect a terminal server with pre-configured IP=192.168.1.1/24.

Basically from the 3750 I need to telnet to 192.168.1.1 and then configure the terminal server with whatever routable IP I want.

Question:

Is this possible without crashing the production Vlan 30?

To my knowledge so far, I should create an "interface vlan" with IP on 192.168.1.0/24 network in order to be able to establish connectivity with the terminal server on port fa1/0/48 from the 3750, right? Then I would assign the port fa1/0/48 to a new Vlan, "vlan 192".

My observation and concern is that if I create such SVI "int vlan 192", immediately Vlan 30 could get shut down due to spanning-tree, correct?

I do not have a PC on site which could let me connect to the same VLAN and access the terminal server from there.

Please let me know if I can make this operation work using the Cisco switch.

1 ACCEPTED SOLUTION

Accepted Solutions
Cisco Employee

Re: VLAN;How can I connect to this pre-configured IP?

Hello,

Creating a new VLAN 192 on your 3750 will not force the existing VLAN 30 to be shut down or blocked due to the STP. Right because of PVST, each VLAN can be individually created, deleted and its state changed without influencing the state in other VLANs - that's a part of what the Per-VLAN STP is about.

However, if you are still concerned about creating a new VLAN, I suggest adding a secondary IP address on the SVI for VLAN30, like,

ip address 192.168.1.254 255.255.255.0 secondary

and assigning the port Fa1/0/48 to VLAN 30 as well. Now you can telnet to 192.168.1.1 and change its settings. Then, according to your needs, you can remove the secondary IP from your VLAN 30 SVI.

Best regards,

Peter

3 REPLIES
Cisco Employee

Re: VLAN;How can I connect to this pre-configured IP?

Hello,

Creating a new VLAN 192 on your 3750 will not force the existing VLAN 30 to be shut down or blocked due to the STP. Right because of PVST, each VLAN can be individually created, deleted and its state changed without influencing the state in other VLANs - that's a part of what the Per-VLAN STP is about.

However, if you are still concerned about creating a new VLAN, I suggest adding a secondary IP address on the SVI for VLAN30, like,

ip address 192.168.1.254 255.255.255.0 secondary

and assigning the port Fa1/0/48 to VLAN 30 as well. Now you can telnet to 192.168.1.1 and change its settings. Then, according to your needs, you can remove the secondary IP from your VLAN 30 SVI.

Best regards,

Peter

New Member

Re: VLAN;How can I connect to this pre-configured IP?

He, he. Very good. I always wondered how the 'secondary' IP could be useful and here it is! That will do it.

In the past I recalled that I crashed one a vlan when I created another vlan interface. I will investigate that scenario and see what happened then. I thought the same about the pvst, so let me see how that happened.

Cisco Employee

Re: VLAN;How can I connect to this pre-configured IP?

Hello,

That inconvenience with VLANs might have happened on 2950 or 2900XL series switches. On 2950, you can create multiple SVI interfaces but as soon as you turn on a particular SVI, all other will be automatically shutdown.

2960 and of course all multilayer switches do not exhibit this behavior. You can have as many activated SVIs as you want (of course, within the device's limits).

Best regards,

Peter

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