Differences between 3550-24-SMI and 3550-24-EMI

Folks:


Here are a few quick questions about the differences between 3550-24-SMI and
3550-24-EMI. One vendor told me it is PERFECTLY OK to purchase 3550-24-SMI
(at a lower cost that EMI) and upgrade same to the 3550-24-EMI which can
then be used for CCNP/CCIE studies. I am trying to determine if there are
any DOWNSIDES to this approach.

* What are the main differences between 3550-24-SMI and 3550-24-EMI ?
* Is it OK to purchase a Catalyst 3550-24-SMI at a lower cost and upgrade
to 3550-24-EMI for use in CCNP/CCIE Lab ?
* Is it true that these two Catalyst Switches have identical hardware but
different IOS ?
* If I upgrade the SMI to EMI do I then have a device identical (in
software & hardware) to an original Catalyst 3550-24-EMI ?



Thanks,
John

 

The EMI enables a richer set of enterprise-class features, including
hardware-based IP Unicast routing (Open Shortest Path First [OSPF],
Interior Gateway Routing Protocol [IGRP], Enhanced IGRP [EIGRP], Border
Gateway Protocol Version 4 [BGPv4]), multicast routing, and policy-based
routing [PBR]).
Both the SMI and the EMI allow for Layer 3 and Layer 4 lookups for QoS
and security

The following features and functions are supported with the EMI:

* Dynamic IP routing protocols for load balancing and constructing
scalable LANs:
*
o OSPF
o IGRP and EIGRP
o BGPv4
* Equal-cost routing for load balancing and redundancy
* Fallback bridging for forwarding of non-IP traffic between two or
more VLANs
* Protocol Independent Multicast (PIM) for IP multicast routing
within a network that enables the network to receive the multicast feed
requested and for switches not participating in the multicast to be
pruned—support for PIM sparse mode (PIM-SM), PIM dense mode (PIM-DM),
and PIM sparse-dense mode
* Distance Vector Multicast Routing Protocol (DVMRP) tunneling for
interconnecting two multicast-enabled networks across nonmulticast networks
* PBR, which allows superior control by enabling flow redirection
regardless of the routing protocol configured

its ok. for ccnp you dont need EMI image

yes

m.

 

[Marcin Strzyzewski]

| > * What are the main differences between 3550-24-SMI and 3550-24-EMI ?
|
| The EMI enables a richer set of enterprise-class features, including
| hardware-based IP Unicast routing

No, SMI does hardware based IP unicast routing just fine, including
static routes and (as far as I remember) RIPv2. Required a reasonably
new IOS version (to have this in SMI).

Steinar Haug, Nethelp consulting,

 

Also, SMI cannot do dot1q on routed ports. This is important if you wanted
to use a 3550 to route between VLANs on a trunk from, say, a rack of
switches. There are means around this (like leave it as a switch port and
route on a SVI) but be aware of this limitation in SMI.
Remember that EMI AND SMI can only route IP. They cannot route
IPX/Apple/DEC.

OSB

 

["One Step Beyond"]

| Also, SMI cannot do dot1q on routed ports. This is important if you wanted
| to use a 3550 to route between VLANs on a trunk from, say, a rack of
| switches.

Can the EMI version do this? Maybe you can post a configuration example.

Steinar Haug, Nethelp consulting,

 

Why would you want to do dot1q on routed interfaces when you can do routing on
SVI interfaces? That is, you setup your physical interface as a trunk port
and then you setup SVI interfaces (i.e. "interface vlan <number>") with the
layer 3 routing and route among the SVI interfaces.

 

[Jason Kau]

| > | Also, SMI cannot do dot1q on routed ports. This is important if you wanted
| > | to use a 3550 to route between VLANs on a trunk from, say, a rack of
| > | switches.
| >
| > Can the EMI version do this? Maybe you can post a configuration example.
|
| Why would you want to do dot1q on routed interfaces when you can do routing on
| SVI interfaces? That is, you setup your physical interface as a trunk port
| and then you setup SVI interfaces (i.e. "interface vlan <number>") with the
| layer 3 routing and route among the SVI interfaces.

Sure, that is the "normal" way of doing it. If, however, you have VLAN
trunks with overlapping VLAN ranges, you cannot use SVIs. Subinterfaces
directly on the ports would be able to handle this, but I don't believe
the 3550 can do subinterfaces directly on the ports. 6500/7600 with
GE-WAN OSM can do it, and the good old 2948G-L3 can do it.

Steinar Haug, Nethelp consulting,

 

3550 can do subinterfaces on the routed ports. Even SMI can do this and
sure you can use secondary addresses on those subinterfaces with SMI.
However, you CANNOT do dot1q encapsulation on a routed port on the SMI
image. You need to use the EMI image to do that. As I said earlier, you'd
want to do this if you had a stack of purely layer 2 swicthes and wanted a
port to act as a trunk connected to one of the 3550 routed ports. You
cannot do this by router on a stick with the SMI image since it does not
support dot1q on routed ports.

OSB

 

["One Step Beyond"]

| 3550 can do subinterfaces on the routed ports. Even SMI can do this and
| sure you can use secondary addresses on those subinterfaces with SMI.
| However, you CANNOT do dot1q encapsulation on a routed port on the SMI
| image. You need to use the EMI image to do that.

I'm willing to believe 3550-EMI and dot1q encapsulation on a routed port
if you can show me a working example - not otherwise. I can't find anything
in the documentation which indicates this is possible.

Steinar Haug, Nethelp consulting,

 

Not sure where you buy you 3550 EMI, but the ones I bought don't support dot1q
encapsulation on routed ports:

interface FastEthernet0/23
no switchport
no ip address
shutdown
end

switch-mb4#conf t
Enter configuration commands, one per line. End with CNTL/Z.
switch-mb4(config)#int f0/23.1
switch-mb4(config-subif)#encapsulation dot1q 10
^
% Invalid input detected at '^' marker.

switch-mb4(config-subif)#

It's running this IOS:

IOS (tm) C3550 Software (C3550-I5Q3L2-M), Version 12.1(13)EA1c,
RELEASE SOFTWARE (fc1)

 

Take my word for it.