Distribution Switch to Access Switch Trunking

Answered Question
Sep 20th, 2007

Hi Experts,

I am just wondering why we can;t just do with "switchport mode trunk" but need to

put "switchport trunk encapsulation dot1q" first before can do trunking on the port.

Error:

Command rejected: An interface whose trunk encapsulation is "Auto" can not be configured to "trunk" mode.

I thought dot1q is only meant for trunking between router LAN and switch?

Hope to get enlightenment again..:)

Thanks!

I have this problem too.
0 votes
Correct Answer by Edison Ortiz about 9 years 2 months ago

No, you don't. Your laptop should be able to communicate to other devices on the same Vlan, by default -and- devices at other Vlan by using the distribution switch Layer3 interface as the default gateway.

The distribution switch and the access switch must have the same Vlan information, specially the Vlan where you laptop resides.

The ip default-gateway information is useful for telneting into the switch and perform remote management tasks.

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Edison Ortiz Thu, 09/20/2007 - 18:14

By default, a switchport is configured as dynamic trunk. It negotiates trunk with another switch automatically. The encapsulation can be dot1q or isl. If no encapsulation is specified at either end, dot1q will be used.

If you set the mode to trunk, the switchport won't negotiate so it needs to know what kind of encapsulation to use.

cindylee27 Thu, 09/20/2007 - 18:38

Thanks Edison..Really understood once you guys explained.. ;)

Another question to follow is I have already establish a connection from Access Switch to Distribution Switch to Core Switch.

I have also configured Vlan at Access Switch. Currently 1 laptop is plugged to the Access Switch with the vlan configured. Do I need to configure ip default-gateway at the access switch in order for me to send udp bootp to the DHCP Server?

DHCP Server is connected at COre Switch.

I have problem detecting the DHCP Server which the range is configured to the VLan iP address range.

Thanks again..

Correct Answer
Edison Ortiz Thu, 09/20/2007 - 18:43

No, you don't. Your laptop should be able to communicate to other devices on the same Vlan, by default -and- devices at other Vlan by using the distribution switch Layer3 interface as the default gateway.

The distribution switch and the access switch must have the same Vlan information, specially the Vlan where you laptop resides.

The ip default-gateway information is useful for telneting into the switch and perform remote management tasks.

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