vlan

Answered Question
Jul 19th, 2010

hi! I know that it's a good practice to have the default vlan 1 shut down in all the switches for security reason, but i'm not too sure what's the actual reason for that? can someone explain on this?

for a spanning-tree command of example.....spanning-tree vlan 10,20,30,40 priority 8192 in my switch. Can i add in a new vlan (eg vlan32) with priority of 8192 into the existing spanning-tree vlan by using the command "spanning-tree vlan 32 priority 8192"? will that add into the vlan 10,20,30,40's command or with this command only vlan 32 will be configured with priority of 8192 and cleared the rest of the spanning tree priority config? Does the same apply to no spanning-tree vlan 32 priority 8192 if i decide to remove vlan32 from the list?

what's the default spanning-tree priority value?

line vty 0 15.....what does the 0 and 15 represent? i noticed that when i key in this command at the bottom of the sh run config i will get

line con 0

line vty 0 4

line vty 5 15

What does this mean?

One last question is that if i did not configure vtp between my switches and i've vlan 2,3,4 in the core sw and only vlan 2 and 4 in my edge switch + only vlan 2 and 4 allowed in the trunk link between the switches. Can i access host assigned with vlan 3 in the core sw from my edge switch? (assumption of all the routes are there)

thx

I have this problem too.
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Correct Answer by Nagaraja Thanthry about 6 years 4 months ago

Hello,

Typically people use VLAN 1 for management purposes. In addition, even the switches use VLAN 1 for sending/receiving management traffic. So, most of the times, network admins use a VLAN other than VLAN 1 for their network. There could be other reasons, that I am unaware of.

With regard to your second question, when you change the priority of a VLAN, it will append the list of other VLANs that have same priority. When you remove a VLAN from that list, only that one VLAN is removed. All other will still have the priority value set as per configuration. The default priority is 32768.

In line vty 0 15, the numbers 0 and 15 represent start and end of the line numbers i.e. you are allowed to open 16 simultaneous telnet/ssh sessions to the switch (using the 16 lines). By default, there are only 5 lines (0 through 4) and there are 11 extended lines (5 through 15). Line Con 0 represents the console port.

To your last question, as long as you have configured routing properly and set the default gateway on your hosts to point to the routed interface, you should be able to communicate between hosts on different vlans irrespective of the VTP usage or the VLAN being present in the switch.

Hope this helps.

Regards,

NT

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Correct Answer
Nagaraja Thanthry Mon, 07/19/2010 - 10:41

Hello,

Typically people use VLAN 1 for management purposes. In addition, even the switches use VLAN 1 for sending/receiving management traffic. So, most of the times, network admins use a VLAN other than VLAN 1 for their network. There could be other reasons, that I am unaware of.

With regard to your second question, when you change the priority of a VLAN, it will append the list of other VLANs that have same priority. When you remove a VLAN from that list, only that one VLAN is removed. All other will still have the priority value set as per configuration. The default priority is 32768.

In line vty 0 15, the numbers 0 and 15 represent start and end of the line numbers i.e. you are allowed to open 16 simultaneous telnet/ssh sessions to the switch (using the 16 lines). By default, there are only 5 lines (0 through 4) and there are 11 extended lines (5 through 15). Line Con 0 represents the console port.

To your last question, as long as you have configured routing properly and set the default gateway on your hosts to point to the routed interface, you should be able to communicate between hosts on different vlans irrespective of the VTP usage or the VLAN being present in the switch.

Hope this helps.

Regards,

NT

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