Configuration Guide User guide

FastIron Configuration Guide 857
53-1002494-02
Layer 3 behavior with MCT
22
Switch S1
!
trunk ethe 3 to 4
!
vlan 100 by port
tagged ethe 3 to 4
router-interface ve 100
!
interface ve 100
ip address 100.1.1.100 255.255.255.0
!
MCT for VRRP or VRRP-E
A simple MCT topology addresses resiliency and efficient load balancing in Layer 2 network
topologies. To interface with a Layer 3 network, MCT is configured with Virtual Router Redundancy
Protocol (VRRP) to add redundancy in Layer 3. The standard VRRP mode is master-backup and all
traffic is forwarded through the master. In VRRP-E server virtualization, multiple VRRP standby
devices are supported and each device can be configured to route to an upstream Layer 3 network.
This provides efficient deployment for both Layer 2 and Layer 3 networks.
The MCT device that acts as backup router needs to ensure that packets sent to a VRRP or VRRP-E
virtual IP address can be Layer 2-switched to the VRRP-E master router for routing. The VRRP or
VRRP-E backup learns the VMAC while processing the VRRP hello message from the VRRP master.
Both data traffic and VRRP or VRRP-E control traffic travel through the ICL unless the short-path
forwarding feature is enabled (VRRP-E only).
Layer 3 traffic forwarding from CEPs to CCEPs
Traffic destined to the CCEPs from the client or CEPs follow the normal IP routing on both master
and backup devices. By default, the best route should not involve the ICL link. Only when the local
CCEP is down will the traffic be re-routed to pass through ICL link.
Layer 3 traffic forwarding from CCEPs to CEPs
For Layer 3 forwarding to work on MCT devices, a dynamic trunk must be configured on the MCT
client. VRRP/VRRP-E and VRRP-E2 SPF should be enabled, if required. Routes should be statically
configured on the MCT cluster devices for all member VLANs.
If VRRP is deployed or VRRP-E is deployed without the short path forwarding feature on the VRRP-E
backup, it is likely that almost 50% (and 100% in the worst case) of CCEP to CEP traffic can pass
through the ICL from the backup to the master device. This fact should be considered when
designing ICL capacity in the network.
ARP resolution
ARP resolution is initially done through the ICL if the S1 MAC address is not already known on the
CCEP at A. When the MDUP message from the cluster peer device moves the S1 MAC from ICL to
CCEP, the ARP is also moved.