Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
Announcements
Webcast-Catalyst9k
New Member

Create Sub.interface of Fast Ethernet and VLANs

Hi,

I know that the fast ethernet can be sub-if to few VLANs, but how can I configure it to TRUNK it with another switch???

Eg:

Fa0/2 to fa0/12 Switch A(2950) configured as VLAN 2 and VLAN 3.

Fa0/1 configured as TRUNKING that connect cross cable to Router A fast ethernet.

I configure Router A Fast Ethernet sub interfaces to IP Addresses of VLAN 2 and 3 segments.

but seems like the trunking is not working,how can i proceed?

thks,!

2 ACCEPTED SOLUTIONS

Accepted Solutions

Re: Create Sub.interface of Fast Ethernet and VLANs

Hi Friend,

You do not have to configure subinterface on the switch side.

Same config for switch

switch(config)#interface fa0/1

switch(config-if)#switchport mode trunk

This will take care of switch config also and router same config I posted in my previous post and this will make your router on stick model ready.

I will appreciate if you rate all post.

Best of Luck for your configs and setup.

Ankur

Gold

Re: Create Sub.interface of Fast Ethernet and VLANs

On the 2950 switch, trunk encapsulation is 802.1Q by default and you have no other choice (like ISL). So you don't have to set encapsulation. In fact, you can't set it.

All you have to do is "switchport mode trunk" and it will trunk any and all VLANs on the switch interface. Use "switchport trunk allowed vlans " command to restrict which VLANs can be on the trunk.

Use the "switchport trunk native vlan " command to define which VLAN is the native, or untagged, one. Make sure the same one is designated as native at each end of the link, or you can run into problems. VLAN 1 is the native VLAN by default; you won't see this command in your switchport config unless you pick another VLAN to be the native one.

No need for sub-interfaces on the switch side, only on the router. And the cable between router and switch should be straight-through, not crossed. (Crossed for router-to-router, or switch-to-switch connection.)

Edited to add:

Wow, there were half a dozen replies before I posted my response! All my main points were covered so my post is redundant. Good luck with your connection.

10 REPLIES

Re: Create Sub.interface of Fast Ethernet and VLANs

Hi Friend,

You need to configure a command on each subinterface as "encapsulation dotq "

Same config

c2600(config)#int fastEthernet 0/0.1

c2600(config-subif)#encapsulation dot1Q 2

c2600(config-subif)#ip address

Also you said you are using a cross cable between a switch and router but you need to have a straight through cable if your switch does support auto mdix then cross cable will work or else you need to have staright cable.

HTH, if yes please rate the post.

Ankur

New Member

Re: Create Sub.interface of Fast Ethernet and VLANs

Thanks Ankur for your reply.

This is for router config. But what about trunking on the Switch(2950) side ?

On the int fa0/1, i could not have encapsulation for the switch side. Do you mean that I need to create sub-interface at the Switch side as well??

I will try cross and straight cable once got the config ready.

thanks again!

Re: Create Sub.interface of Fast Ethernet and VLANs

HI

u have to use the encapsulation at the switch side whatever it is i.e ISL or DOT1Q and it should be set as a trunk link.

u need not create any subinterface on the siwtch side.

Thanks

Mahmood

New Member

Re: Create Sub.interface of Fast Ethernet and VLANs

Mahmood,

Do have the commands/configuration at the switch side?

Because I could not find encapsulation at the switch side when i go to int fa0/1 level.

I am stuck at the switch side currently..

I only see DOT1X instead of ENCAPSULATION when i do ? at the int fa0/1 level.

thanks!

Re: Create Sub.interface of Fast Ethernet and VLANs

HI

As Ankur said that if it is 2950 switch u have the default encapsulation dot1q so u will not able to see the encapsulation command.

Follow the config given by Ankur u will be get going.

Thanks

Mahmood

Re: Create Sub.interface of Fast Ethernet and VLANs

Hi Mahmood,

2950 supports only dot1q and it does not support isl so encapsulation command will not work.

Regards,

Ankur

Re: Create Sub.interface of Fast Ethernet and VLANs

Hi Friend,

You do not have to configure subinterface on the switch side.

Same config for switch

switch(config)#interface fa0/1

switch(config-if)#switchport mode trunk

This will take care of switch config also and router same config I posted in my previous post and this will make your router on stick model ready.

I will appreciate if you rate all post.

Best of Luck for your configs and setup.

Ankur

Gold

Re: Create Sub.interface of Fast Ethernet and VLANs

On the 2950 switch, trunk encapsulation is 802.1Q by default and you have no other choice (like ISL). So you don't have to set encapsulation. In fact, you can't set it.

All you have to do is "switchport mode trunk" and it will trunk any and all VLANs on the switch interface. Use "switchport trunk allowed vlans " command to restrict which VLANs can be on the trunk.

Use the "switchport trunk native vlan " command to define which VLAN is the native, or untagged, one. Make sure the same one is designated as native at each end of the link, or you can run into problems. VLAN 1 is the native VLAN by default; you won't see this command in your switchport config unless you pick another VLAN to be the native one.

No need for sub-interfaces on the switch side, only on the router. And the cable between router and switch should be straight-through, not crossed. (Crossed for router-to-router, or switch-to-switch connection.)

Edited to add:

Wow, there were half a dozen replies before I posted my response! All my main points were covered so my post is redundant. Good luck with your connection.

New Member

Re: Create Sub.interface of Fast Ethernet and VLANs

Ankur,Koniql...Both of you are right!

You guys are the man! I will rate both of you for tis resolution! :D

Koniql,Although your post is redundant, but your this statement really enlightent me! :)

""And the cable between router and switch should be straight-through, not crossed. (Crossed for router-to-router, or switch-to-switch connection.) ""

thanks for all again!

Re: Create Sub.interface of Fast Ethernet and VLANs

hi,,,

ya u need to have stright-through cable to connect ...

regards

Devang

4435
Views
15
Helpful
10
Replies
CreatePlease to create content