Cisco Nexus 5000 Series - Page 27

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Cisco Nexus 5000 Series NX-OS Interfaces Operations Guide, Release 5.0(3)N2(1)
Chapter 2 Cisco Nexus 5500 Platform Layer 3 and vPC Operations
Layer 3 Forwarding for Packets to a Peer Switch MAC Address
MAC address (when FHRP is enabled) or its own MAC address. In this scenario, a Cisco Nexus 5500
Platform switch can forward the traffic to the peer using a peer link and the peer switch performs the
Layer 3 forwarding.
The above scenario often happens with some filers or with Layer 3 peering over vPC. In the case of filers,
they may achieves improved load balance and better performance by forwarding traffic to the
Burnt-in-Address (BIA) of the routers instead of the HSRP MAC.
Figure 2-2 shows that when the NAS filer sends out packets with N5k-1’s MAC RMAC-A as the
destination MAC, the packets can be sent over to the N5k-2 switch due to the port channel hashing.
Figure 2-2 vPC and Peer-Gateway
Another scenario that could lead to this situation is when a router is connected to a Cisco Nexus 5500
Platform in a vPC topology.
Figure 2-3 Connecting to a Router in a vPC Topology
N5k-2N5k-1
RMAC-BRMAC-A
L3
L2
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HSRP
Active
HSRP
Standb
y
RMAC-A
239431
VPC Topology L3 Topology
N5k-1
N5k-1 N5k-2
N5k-2
R