Very Computer

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 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
prunedsupport 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

Quote:> *   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 ?

Quote:> *   Is it true that these two Catalyst Switches have identical hardware but
> different IOS ?

Quote:> *   If I upgrade the SMI to EMI do I then have a device identical (in
> software & hardware) to an original Catalyst 3550-24-EMI ?

m.

|   > *   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).

OSB

|   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.

--
Jason Kau
http://www.cnd.gatech.edu/~jkau

|  > |   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.

OSB

|   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.

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.
|  


|   > ["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.

I'm afraid your word is absolutely useless here - it doesn't help me
find out *how* to do this if it were indeed possible. So until this is
documented, or somebody shows a working example, I'm going to assume
it is *not* possible.