MSM Layer 3 Switching
The initial Layer 3 switching engine for the Catalyst 6000 family consisted of the Multi-layer Switch Model (MSM). Based on Catalyst 8510 technology, the MSM provides a router-on-a-stick configuration integrated into the Catalyst 6000 chassis. Therefore, the MSM brings the power of the 8510 to the Catalyst 6000 family (namely IP and IPX routing at approximately 5 million packets per second [mpps]).
Note
The MSM contains a faster CPU that is currently used in the 8510.
From a configuration standpoint, the MSM connects to the Catalyst 6000 backplane via four Gigabit Ethernet interfaces. These interfaces are labeled as GigabitEthernet 0/0/0, 1/0/0, 3/0/0, and 4/0/0. Note that 2/0/0 is not used and that these numbers do not refer to the slot where the MSM is installed (they are always locally significant). Figure 18-1 illustrates the Catalyst 6000 backplane connections.
Figure 18-1. Conceptual Diagram of the MSM
The MSM supports two primary types of inter-VLAN router configurations:
- Using each of the Ethernet interfaces as a separate router port
- Grouping all four of the Gigabit Ethernet interfaces into a single EtherChannel bundle
One important point to note is that both options require that configuration commands be entered on both the Layer 2 Supervisor and the Layer 3 MSM. The Supervisor configuration is used to assign the MSM interfaces to VLANs or to an EtherChannel bundle, whereas the MSM configuration is used to actually configure the routing process.
- Tip
The MSM requires a coordinated configuration on both the Catalyst 6000 Supervisor and the MSM itself.
Using each of the Gigabit Ethernet interfaces as a separate router port is the simplest of the two configuration types. For example, the partial configuration shown in Example 18-1 configures the interfaces to handle routing for VLANs 1–4.
Example 18-1 Using the MSM Interfaces as Unique Router Ports
interface GigabitEthernet0/0/0 ip address 10.0.1.1 255.255.255.0 no ip redirects no ip directed-broadcast ! interface GigabitEthernet1/0/0 ip address 10.0.2.1 255.255.255.0 no ip redirects no ip directed-broadcast ! interface GigabitEthernet3/0/0 ip address 10.0.3.1 255.255.255.0 no ip redirects no ip directed-broadcast ! interface GigabitEthernet4/0/0 ip address 10.0.4.1 255.255.255.0 no ip redirects no ip directed-broadcast
This configuration is conceptually identical to the router-on-a-stick configuration discussed in the “One-Link-per-VLAN” section of Chapter 11. Each interface is configured with a single VLAN and an IP address. Example 18-2 shows the corresponding Supervisor configuration that is used to assign each MSM interface to a separate VLAN.
Example 18-2 Supervisor Configuration for Unique Router Ports
Cat6000 (enable) set vlan 1 7/1 VLAN Mod/Ports ---- ----------------------- 1 1/1-2 2/1-2 3/3-24 4/3-24 5/1-2,5/5-8 7/1-4 Cat6000 (enable) set vlan 2 7/2 VLAN 2 modified. VLAN 1 modified. VLAN Mod/Ports ---- ----------------------- 2 1/1-2 5/7 7/1-4 Cat6000 (enable) set vlan 3 7/3 Vlan 3 configuration successful VLAN 3 modified. VLAN 2 modified. VLAN Mod/Ports ---- ----------------------- 3 1/1-2 5/7 7/1-4 Cat6000 (enable) set vlan 4 7/4 Vlan 4 configuration successful VLAN 4 modified. VLAN 3 modified. VLAN Mod/Ports ---- ----------------------- 4 1/1-2 5/7 7/1-4
This assigns each MSM router interface to a separate Layer 2 VLAN. Note that Example 18-2 assumes the MSM is located in Slot 7.
Although the configuration in Example 18-1 and Example 18-2 correctly provides routing services, you can obtain a much more flexible configuration by grouping all four of the Gigabit Ethernet interfaces into a single EtherChannel bundle. By doing so, certain VLANs are not tied to specific Gigabit Ethernet ASICs onboard the MSM, allowing for a more even distribution of traffic.
To create an EtherChannel bundle on the MSM, simply follow the steps outlined in the “EtherChannel” section of Chapter 11:
- Create one subinterface for each VLAN using the interface port-channel port-channel.subinterface-number command.
- Configure each subinterface. At a minimum, this consists of assigning a VLAN with the encapsulation isl vlan-identifier command and an IP and/or IPX address (802.10 can also be used). (It is possible to configure bridging but not recommended—see the “Integration between Routing and Bridging” section of Chapter 11.)
- Assign all four Gigabit Ethernet interfaces to the Port-channel interface using the channel-group channel-number command.
Note
Although generally not useful, it is possible to create more than one Port-channel interface and assign different Gigabit Ethernet interfaces to each.
For instance, Example 18-3 displays the complete configuration from an MSM that has been configured with a single EtherChannel interface to the Catalyst 6000 backplane.
Example 18-3 A Complete MSM Configuration Using EtherChannel
no service pad service timestamps debug uptime service timestamps log uptime no service password-encryption ! hostname MSM ! ! ip subnet-zero ipx routing 0050.730f.6a0c ! ! interface Port-channel1 no ip address no ip directed-broadcast hold-queue 300 in ! interface Port-channel1.1 encapsulation isl 1 ip address 10.0.1.2 255.255.255.0 no ip redirects no ip directed-broadcast ipx encapsulation NOVELL-ETHER ipx network A000100 standby 1 timers 1 3 standby 1 priority 200 standby 1 preempt standby 1 ip 10.0.1.1 ! interface Port-channel1.2 encapsulation isl 2 ip address 10.0.2.2 255.255.255.0 no ip redirects no ip directed-broadcast ipx encapsulation NOVELL-ETHER ipx network A000200 standby 2 timers 1 3 standby 2 priority 100 standby 2 preempt standby 2 ip 10.0.2.1 ! interface Port-channel1.3 encapsulation isl 3 ip address 10.0.3.1 255.255.255.0 no ip redirects no ip directed-broadcast ipx encapsulation NOVELL-ETHER ipx network A000300 ! interface GigabitEthernet0/0/0 no ip address no ip directed-broadcast no negotiation auto channel-group 1 ! interface GigabitEthernet1/0/0 no ip address no ip directed-broadcast no negotiation auto channel-group 1 ! interface GigabitEthernet3/0/0 no ip address no ip directed-broadcast no negotiation auto channel-group 1 ! interface GigabitEthernet4/0/0 no ip address no ip directed-broadcast no negotiation auto channel-group 1 ! router eigrp 1 passive-interface Port-channel1.1 passive-interface Port-channel1.2 network 10.0.0.0 ! ip classless ! ! line con 0 transport input none line aux 0 line vty 0 4 no login ! no scheduler allocate end
Example 18-3 configures three subinterfaces on the EtherChannel interface: one each for VLAN 100, VLAN 101, and VLAN 102. All four of the Gigabit Ethernet interfaces have been included in the channel to provide a single high-speed pipe to the rest of the Catalyst.
To create the EtherChannel on the Layer 2 Supervisor, the commands shown in Example 18-4 are required.
Example 18-4 Supervisor Configuration for Unique Router Ports
Cat6000> (enable) set port channel 7/1-4 on Ports 7/1-4 channel mode set to on. Cat6000> (enable) set trunk 7/1 nonegotiate isl Port(s) 7/1 trunk mode set to nonegotiate. Port(s) 7/1 trunk type set to isl.
These two commands first assign all four MSM interfaces to a single EtherChannel interface and then enable ISL trunking across the entire bundle. (Although the trunk command is only entered for Port 7/1, it is automatically applied to all four ports.)
Note
Notice that the MSM, being derived from 8500 technology, functions under the switching router form of Layer 3 switching discussed in Chapter 11.