Configuration Guide User guide

858 FastIron Configuration Guide
53-1002494-02
Layer 3 behavior with MCT
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If S1 triggers an ARP request, it generally does so for the default gateway address (virtual IP
address if VRRP is deployed). This ARP request can reach A either directly from S1, or through B.
• If the ARP request reaches A directly, it replies through the same port on which it learned S1's
MAC address.
• If the request is by way of B, S1's ARP response will be learned on the ICL first, then it will move
to the CCEP link when the MDUP message for S1's MAC address is received from B.
VRRP or VRRP-E configuration with MCT
In Figure 103, MCT devices A and B both need to ensure packets sent to VRRP-E virtual IP address
can be Layer 2-switched to the VRRP-E master router for routing. Both data traffic and VRRP-E
control traffic travel through ICL, unless the short-path forwarding feature is enabled. The VRRP or
VRRE-E virtual MAC address will be learned on ICL ports on backup routers through the ICL. The
VRRP or VRRP-E master router will broadcast hello packets to all VLAN member ports, including ICL
ports.
FIGURE 103 Example of MCT configuration with Layer 2 switching
Configuration considerations
• MCT devices must have complete routing information using static routes for Layer 3
forwarding.
ICL
Gateway Gateway
VRRP-E backupVRRP-E master
CCEP
CCEP
Device A
CEP CEP
Clients Clients
Trunk Group
MCT
unaware
switch
MCT cluster
Device B