In a Cisco Unified Computing System, What is the “designated receiver” port in end-host mode used for?
A. Sending all broadcasts
B. Receiving all traffic from upstream switches
C. Receiving broadcast traffic
D. Negotiating spanning tree with upstream switches
E. Learning MAC addres?ses from upstream switch?es
Correct Answer: C
Explanation/Reference:
Explanation:
UCS uses the concept of a “designated receiver” (DR) port that is the single port (or port channel) chosen by UCSM to receive all multicast and broadcast traffic for all VLANs defined on the Fabric Interconnect (FI). To make this clear, UCS receives all multicast/broadcast traffic on this port only and drops broadcast/multicast traffic received on all other ports. Unless you have DJL2, this method works really well. If you do have DJL2, this would lead to a problem if you defined the above VLAN configuration and plugged it into pre-2.0 UCS (in EHM). In this situation, UCS would choose a designated receiver port for ALL VLANs (10-60) and assign it to one of the available uplinks. Let’s say the system chose port 1 (VLANs 10, 20, and 30) for the DR. In that situation, those networks (10, 20, 30) would work correctly, but VLANs 40, 50, and 60 (plugged into port 2) would not receive any broadcast and multicast traffic at all. The FI will learn the MAC addresses of the destinations on port 2 for 40, 50 and 60, but necessary protocols like ARP, PXE, DHCP (just to name a few) would be broken for these networks. In case you’re wondering, pin groups do not solve this problem so don’t waste your time. Instead, you need UCS 2.0+ and DJL2 which allows specific VLANs to be pinned to specific uplink ports. In addition, you now have a DR port for each defined VLAN as opposed to globally for the each FI.
Reference: http://jeffsaidso.com/2013/04/enm-source-pinning-failed-a-lesson-in-disjoint-layer-2/
