Identify Layer 2 Switch or Layer 3 Switch ?

[Anup Sasikumar]

Hi Experts ,

I can understand it 's one of those very basic questions , but how do I identify a Switch is Layer 2 or Layer 3 ?

Looking through # show version command and checking the IOS version to be IP BASE or LAN BASE . Is it the right way ?

Cisco 2960 is a Layer 2 or a Layer 3 Switch ? I noticed that access-lists could be configured which means that it 's a Layer 3 Switch , right?

--------------------------------------------------------------------------------------------------------------------

Cisco IOS Software, C2960 Software (C2960-LANBASE-M), Version 12.2(25)SEE2, REL

ASE SOFTWARE (fc1)

Copyright (c) 1986-2006 by Cisco Systems, Inc.

Compiled Fri 28-Jul-06 04:33 by yenanh

Image text-base: 0x00003000, data-base: 0x00AA2F34

ROM: Bootstrap program is C2960 boot loader

BOOTLDR: C2960 Boot Loader (C2960-HBOOT-M) Version 12.2(25r)SEE1, RELEASE SOFTW

RE (fc1)

SWCENTRALF0-1 uptime is 2 weeks, 2 days, 11 hours, 55 minutes

System returned to ROM by power-on

System restarted at 16:00:10 AST Wed Jan 25 2012

System image file is "flash:c2960-lanbase-mz.122-25.SEE2/c2960-lanbase-mz.122-2

.SEE2.bin"

cisco WS-C2960-48TC-L (PowerPC405) processor (revision B0) with 61440K/4088K by

es of memory.

Processor board ID FOC1052X1JT

Last reset from power-on

2 Virtual Ethernet interfaces

48 FastEthernet interfaces

2 Gigabit Ethernet interfaces

The password-recovery mechanism is enabled.

64K bytes of flash-simulated non-volatile configuration memory.

Base ethernet MAC Address       : 00:1A:A2:BA:1C:80

Motherboard assembly number     : 73-9835-07

Power supply part number        : 341-0097-02

Motherboard serial number       : FOC10514M8J

Power supply serial number      : DCA105084VP

Model revision number           : B0

Motherboard revision number     : C0

Model number                    : WS-C2960-48TC-L

System serial number            : FOC1052X1JT

Top Assembly Part Number        : 800-26672-02

Top Assembly Revision Number    : C0

Version ID                      : V02

CLEI Code Number                : COM3F00BRA

Hardware Board Revision Number  : 0x02

Switch   Ports  Model              SW Version              SW Image

------   -----  -----              ----------              ----------

*    1   50     WS-C2960-48TC-L    12.2(25)SEE2            C2960-LANBASE-M

Configuration register is 0xF

------------------------------------------------------------------------------------------------------------------------

But how come it 's possible that the switch has a LAN BASE IOS image and Layer 3 access lists can also be configured ?

Please provide your valuable thoughts on this .

[nkarpysh]

Hi Anup,

That all depends on how you understand Layer 2 and 3. Let's consider it with following explanation by Cisco:

As described on Cisco's website (http://www.cisco.com/univercd/cc/td/doc/cisintwk/idg4/nd2002.htm):

"The difference between Layer 2 and Layer 3 switching is the type of information inside the frame that is used to determine the correct output interface. With Layer 2 switching, frames are switched based on MAC address information. With Layer 3 switching, frames are switched based on network-layer information."

So the difference in if packet can be only switched (using ethernet frame header) or both switched and routed (using IP packet header). Cisco 2XXX platforms are all layer 2. Cisco 3xxx platform support ip routing and the layer 2 and 3 capable.

Layer 2 switches can do some limited IP packet header inspection (like in ACL) but they are not able to perform routing decision thus stay layer 2 only.

Hope this helps.

Nik

[Leo Laohoo]

Cisco 2XXX platforms are all layer 2.

Yes and no.  I agree with Nik that the 2XXX are Layer 2 "only".  Recently, Cisco has announced that the 2960 can support "limited" routing capability starting from IOS version 12.2(55)SE3.

[Joseph W. Doherty]

Disclaimer

The     Author of this posting offers the information contained within this     posting without consideration and with the reader's understanding  that    there's no implied or expressed suitability or fitness for any   purpose.   Information provided is for informational purposes only and   should not   be construed as rendering professional advice of any kind.   Usage of  this  posting's information is solely at reader's own risk.

Liability Disclaimer

In     no event shall Author be liable for any damages whatsoever   (including,   without limitation, damages for loss of use, data or   profit) arising  out  of the use or inability to use the posting's   information even if  Author  has been advised of the possibility of  such  damage.

Posting

Sometimes when a L2 switch has features related to L3 packet contents, as your example of L3 ACLs, it might be referred to at L2+ or L2 enhanced, but as Nik describes, its forwarding is still based on L2 MACs.

As Leo notes, the 2960(-S), starting with 12.2(55) SE now supports a very limited routing capability, see:

http://www.cisco.com/en/US/docs/switches/lan/catalyst2960/software/release/12.2_55_se/configuration/guide/swipstatrout.html.

[naresh.narang]

L3 function on 2960 is very limited. You need to be able to run routing protocols to get it.

Sent from Cisco Technical Support iPhone App

[Anup Sasikumar]

Thanks for all the information . Is it possible that I can configure an access-list on a Layer 3 interface vlan to restrict access,on a 2960 Switch ? Please share your thoughts

[sbhadrav@cisco.com]

Look at the product code of the switch.  If the switch ends with "EMI" then it's a Layer 3 switch.  If it's "SMI" then it could be a layer 2 only switch.

TO convert the appliance from Layer 2 to Layer 3, you need to have a hardware upgrade.  I am not sure how to determine if your appliance was upgraded from SMI to EMI.

[Santhosh Abimanyu]

Hi ,

How to find SMI , EMI in Switch , Can please explain 

[RokasK]

Hi,

Good answers!

Im doing my CCNA and using simulator which is of course not the best solution to learn CLI however in the simulator I see network topologies and based on them I need to make networking decisions where I cant see model name or serial number etc. So the question would be what is the shortest way to identify (indirectly) whether is l2 or l3 switch? My thoughts is that if l3 makes decisions based on IP what command for example maybe one of "show" would distinguish from l2 switch?