Cisco 2960s Switches Can Route
As Cisco user know, Cisco 2960s can route now. As of 12.2(55)SE, Cisco 2960s switches are layer 3 switches (with some limitations mentioned later).
Configuring 2960s to route is pretty simple. The Switch Database Management template (SDM) needs to be changed to “lanbase-routing”. A reboot is (always) needed after changing the SDM template. After reboot, it’s just like enabling routing on any other L3 switch with the command “ip routing” from global config.
First we’ll change the SDM template:
SwitchA(config)#sdm prefer lanbase-routing
Changes to the running SDM preferences have been stored, but cannot take effect until the next reload.
Use 'show sdm prefer' to see what SDM preference is currently active.
System configuration has been modified. Save? [yes/no]: y
Proceed with reload? [confirm]
After changing the SDM template, we are reminded that we’ll need to reboot and also given a command to verify the change after the next boot.
Now we verify:
SwitchA#show sdm prefer
The current template is "lanbase-routing" template.
The selected template optimizes the resources in
the switch to support this level of features for
8 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: 4.25K
number of directly-connected IPv4 hosts: 4K
number of indirect IPv4 routes: 0.25K
number of IPv4 policy based routing aces: 0
number of IPv4/MAC qos aces: 0.125k
number of IPv4/MAC security aces: 0.375k
The change was successful and we’re given the details about this SDM template.
Now seems like a good time to touch on the limitations of the layer 3 capabilities on Cisco 2960s. As we see in the output above, we’re limited to 8 routed interfaces. These will be SVIs. At this point, thCatalyst e 2960s don’t support routed physical interfaces (“no switchport”). Another important note is that we’re only allowed 16 static routes and there is no dynamic routing capability.
Now we’ll enable IP routing and configure a couple SVIs:
SwitchA(config)#int vlan 15
SwitchA(config-if)#ip add 192.168.15.1 255.255.255.0
SwitchA(config-if)#int vlan 25
SwitchA(config-if)#ip add 192.168.25.1 255.255.255.0
SwitchA#sh ip route
C 192.168.15.0/24 is directly connected, Vlan15
C 192.168.25.0/24 is directly connected, Vlan25