Smart questions
Smart answers
Smart people
INTELLIGENT WORK FORUMS
FOR COMPUTER PROFESSIONALS

Member Login
Remember Me
Forgot Password?
Join Us!

Come Join Us!

Are you a
Computer / IT professional?
Join Tek-Tips now!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
Join Tek-Tips
*Tek-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

LINK TO THIS FORUM!

Add Stickiness To Your Site By Linking To This Professionally Managed Technical Forum.
Just copy and paste the
code below into your site.

Tek-Tips LinkedIn® Group

Partner With Us!

"Best Of Breed" Forums Add Stickiness To Your Site
Partner Button
(Download This Button Today!)

Feedback

"...If there has ever been a justification needed for access to the net during working hours, just referring to this site should suffice. Fantastic!..."
More...

Geography

Where in the world do Tek-Tips members come from?
Click Here To Find Out!

Tek-Tips Shirts!

Get Tek-Tips Swag
Get your
Tek-Tips Forums
SWAG here!
Home > Forums > Communications Rack > Networking > Cisco: Switches Forum

ws-c3550-24 support subinterfaces

thread558-1688487
Read More Threads Like This One
cammy (TechnicalUser)
17 Jul 12 16:00
Hi

Does anyone have a definitive answer on whether the C3550-24 running the EMI image can support subinterfaces in the form int fa0/1.1 ?

I can't get it working but this chap seems to have:

http://www.tek-tips.com/viewthread.cfm?qid=1559316

Thanks

Cammy
VinceWhirlwind (TechnicalUser)
17 Jul 12 21:25
I'd have to see it to believe it.
The 3500 is a switch. It doesn't use subinterfaces, it uses SVIs, as per my config example in the thread you've referenced.
chieftan (MIS)
18 Jul 12 3:40
As per vincewhirlwind....I would like to see that be achieved...... He either got the name of the device wrong or maybe he super glued a little port next to the other port and called it a subint (Thats just a bad try at humour....apologies)....
cammy (TechnicalUser)
18 Jul 12 8:24
Thanks

If the thread wasn't closed I'd mark it as inappropriate. smile

I've wasted time trying to get it working that way.
cammy (TechnicalUser)
23 Jul 12 15:48
So what is the difference between the ports on layer 3 switches that you can create subinterfaces on some and not others?

ie c3550-24-emi & WS-C3750G-24T

Thanks

Cammy
VinceWhirlwind (TechnicalUser)
23 Jul 12 19:41
Routers have routed interfaces. These interfaces support sub-interfaces. Sub-interfaces are required to create an 802.1q trunk.

Switches have interfaces that can be configured as either switched or routed interfaces. Routed interfaces do not support sub-interfaces. To create an 802.1q trunk, you configure the port as a switched interface and associate it with VLANs which have VLAN interfaces associated with them.

You seem to be implying that 3750s have routed ports that support sub-interfaces. Unless you have some very special code running your 3750, this is false.
Switch routed interfaces do not support sub-interfaces.
http://www.cisco.com/en/US/docs/switches/lan/catal...
cammy (TechnicalUser)
24 Jul 12 12:44
Possibly supports subinterfaces but not vlan subinterfaces?

CODE

Router#sh ver
Cisco IOS Software, C3750 Software (C3750-IPSERVICES-M), Version 12.2(25)SEB4, RELEASE SOFTWARE (fc1)
Copyright (c) 1986-2005 by Cisco Systems, Inc.
Compiled Tue 30-Aug-05 15:47 by yenanh

ROM: Bootstrap program is C3750 boot loader
BOOTLDR: C3750 Boot Loader (C3750-HBOOT-M) Version 12.1(11r)AX, RELEASE SOFTWARE (fc1)

Router uptime is 1 year, 15 weeks, 2 days, 5 hours, 24 minutes
System returned to ROM by power-on
System image file is "flash:c3750-ipservices-mz.122-25.SEB4/c3750-ipservices-mz.122-25.SEB4.bin"


CODE

interface GigabitEthernet1/0/9
 switchport trunk encapsulation dot1q
 switchport mode trunk
!
interface GigabitEthernet1/0/9.1
 ip access-group 1 in
VinceWhirlwind (TechnicalUser)
25 Jul 12 2:10
Ah, I see the distinction. So what is the purpose of your switchport subinterfaces? Something like private VLANs?
VinceWhirlwind (TechnicalUser)
25 Jul 12 2:46
It's worth pointing out that the switchport you're displaying is not a routed interface.
cammy (TechnicalUser)
25 Jul 12 7:28
Hi

I'm not sure what the subinterfaces would be used for on the 3750. They won't accept the ip address command, so as you say, not routed interfaces.
telcoguy (MIS)
26 Jul 12 6:44
Cammy, in order to make a port routed, you'd have to tell it to not be a switchport.
After that you can make it a routed port, and put subintertfaces on as well if you like.
Providing you have the right IOS:
On a 3750 with IPbase image:
interface GigabitEthernet1/0/2
no switchport
ip address 5.6.7.8 255.255.255.0 secondary
ip address 1.2.3.4 255.255.255.0
ADB100 (TechnicalUser)
26 Jul 12 7:29
telcoguy - secondary IP addresses are completely different to sub-interfaces. Secondary IP addresses are a workaround for badly designed networks where you want to have have multiple IP networks/subnets on the same physical layer-2 network (broadcast domain). Sub-interfaces are separate logical interfaces that the router treats as completely separate entities.
Although it *appears* in some IOS versions you can create sub-interfaces on the fixed config layer-3 switches (3550, 3560 & 3750) they are useless.

http://www.cisco.com/en/US/docs/switches/lan/catal...
Read More Threads Like This One

Reply To This Thread

Posting in the Tek-Tips forums is a member-only feature.

Click Here to join Tek-Tips and talk with other members!

Back To Forum

Back To Cisco: Switches

Close Box

Join Tek-Tips® Today!

Join your peers on the Internet's largest technical computer professional community.
It's easy to join and it's free.

Here's Why Members Love Tek-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close