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SRM and IP Multicast
With SRM, the VLAN interfaces on the nondesignated router are in a down state. Even after a failover, these interfaces will
not move into an up state until the supervisor engine verifies that the VLAN has at least one connected physical interface in
the forwarding state. Thisinterruption causesthe supervisor engineto delete allmulticast entries inthe PFCx andthis disrupts
multicast forwarding. As an enhancement to the original SRM implementation, Cisco Catalyst OS release 7.1 provides
support for IP Multicast stateful redundancy.When SRM is enabled in Cisco Catalyst OS version 7.1, the multicast flows are
preserved during a failover.
Supervisor and MSFC Failover Tests
A test environment was created to demonstrate sample high-availability switchover scenarios and record the corresponding
failover times.The testsetup included oneCisco Catalyst 6509chassis with dualsupervisor engine 2 linecards running Cisco
Catalyst OS version 7.2.2 or MSFC2 hardware running Cisco IOS Software Release 12.1(11b)E4. These tests were intended
to be basic and easily demonstrated. The testing mechanism was pings between two end devices connected directly to the
switch. Spanning-Tree was enabled onthe ports inuse for allscenarios. Tests were initiatedby resetting the switchsupervisor
engine. Each scenario was tested eight times and the results were averaged.
Layer 2 Failover
For Layer 2 traffic between two end stations within the same VLAN , the failover resulted in a one or two ping timeout
(approximately one- or two-second failover time).
Note:
This test can be performed on a supervisor engine without an MSFC.
Layer 3 Failover
For Layer 3 traffic, a common test environment was created for measuring the supervisor or MSFC failover of a single Cisco
Catalyst6500 Seriesconfigured firstwith DRMandthen withSRM. Thetwopinging devices wereplacedin separateVLANs.
The basic software configuration included enabling the High Availability feature on the Cisco Catalyst OS and then either
DRM or SRM redundancy in the Cisco IOS Software on the MSFC2. The complete configurations are shown below.
SRM
hostname SRM
!
redundancy
high-availability
single-router-mode
!
interface Vlan20
ip address 10.20.1.3 255.255.255.0
no ip redirects
!
interface Vlan30
ip address 10.30.1.3 255.255.255.0
no ip redirects
!
end
