I recently configured a pair of Cisco 2960-S switches it was in fact a very simple config a pair of vlans a default gateway. I mean it was about as plain Jane as you can get yet when I tried to add a static route using the following command
Switch(config)# Config t
Switch(config)# IP route 0.0.0.0 0.0.0.0 10.1.1.1
It promptly told me that no such command as IP route existed, really a switch that I can’t add a static route too….
I scratched my head for a few moments and then looked at the SDM profile. And lo and behold it was set to the default SDM. Now the SDM is the Switch Database Management that is kept in a specialized piece of memory called the TCAM or Ternary Content Addressable Memory, this is used by the switch for forward table lookups.
This is the first time I have seen a 2960-S shipped with a default SDM simply because if you install a switch a static route is usually required for any LAN setup you might think of doing, unless it’s a standalone switch that never has to send traffic anywhere but its own VLANS.
I typed the following on a 2960-S, which returned
Switch# Sh SDM pre
The current template is “default” template.
The selected template optimizes the resources in
the switch to support this level of features for
0 routed interfaces and 255 VLANs.
number of unicast mac addresses: 8K
number of IPv4 IGMP groups: 0.25K
number of IPv6 multicast groups: 0.25K
number of IPv4/MAC qos aces: 0.375k
number of IPv4/MAC security aces: 0.375k
number of IPv6 policy based routing aces: 0
number of IPv6 qos aces: 0
number of IPv6 security aces: 0.125k
Changing the SDM is fairly simple and straightforward.
Switch(config)# Config t
Switch(config)# SDM pre (profile name)
Now on a 2960-S you only have two profiles default and Lanbased-routing, other series switches have more profiles available.
Switch(config)# SDM pref lanbase-routing
I did a reload on the device for the changes to take effect and then repeated the same commands
Switch# Sh SDM pre
The current template is “lanbase-routing” template.
The selected template optimizes the resources in
the switch to support this level of features for
0 routed interfaces and 255 VLANs.
number of unicast mac addresses: 4K
number of IPv4 IGMP groups + multicast routes: 0.25K
number of IPv4 unicast routes: 4.875k
number of directly-connected IPv4 hosts: 4K
number of indirect IPv4 routes: 0.875k
number of IPv6 multicast groups: 0.25K
number of directly-connected IPv6 addresses: 0.25K
number of indirect IPv6 unicast routes: 0
number of IPv4 policy based routing aces: 0
number of IPv4/MAC qos aces: 0.375k
number of IPv4/MAC security aces: 0.375k
number of IPv6 policy based routing aces: 0
number of IPv6 qos aces: 0
number of IPv6 security aces: 0.125k
And the world was again whole and made perfect sense, why these devices shipped with a default policy that would be of no use in the real world is a question beyond this article but once changed velvet robes parted and wine flowed freely to the people once again.