ws-c3550-24 support subinterfaces

[cammy]

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]

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]

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]

Thanks

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

I've wasted time trying to get it working that way.

 

[cammy]

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]

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/swi..._see/configuration/guide/swint.html#wp1640782

 

[cammy]

Possibly supports subinterfaces but not vlan subinterfaces?

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"

interface GigabitEthernet1/0/9
 switchport trunk encapsulation dot1q
 switchport mode trunk
!
interface GigabitEthernet1/0/9.1
 ip access-group 1 in

 

[VinceWhirlwind]

Ah, I see the distinction. So what is the purpose of your switchport subinterfaces? Something like private VLANs?

 

[VinceWhirlwind]

It's worth pointing out that the switchport you're displaying is not a routed interface.

 

[cammy]

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]

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]

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/swi...5_se/configuration/guide/swint.html#wp1869201