You are about to migrate a customer network to use a VSS. Which of these statements is true
about a VSS?
A.
The VSS switch must be the root bridge for all VLANs and is automatically designated.
B.
The VSS switch is defined in RFC 4318 as a managed object.
C.
The PAgP+ or LACP protocols are used to maintain the operational state of the VSS devices.
D.
A VSS interoperates with a virtual port channel.
E.
The 802.1 Q or ISL protocols are used to maintain the operational state of the VSS devices.
F.
A VSS increases the size of the spanning-tree domain.
Explanation:
Root Switch and Root Guard Protection
The root of the STP should always be the VSS. Use a statically-defined, hard-coded value for the
spanning tree root so that no other switches in the network can claim the root for a given spanning
tree domain. Use either Root Guard on a link of VSS-facing access-layer switch or enable it at
access-layer switch user port (although the later does not prevent someone from replacing
access-layer switch with another switch that can take over as root). The root change might not
affect forwarding in non-looped designs (root selection matter only when alternate path (loop) is
presented to STP); however, the loss of BPDU or inconstancies generated by a noncompliant
switch becoming root could lead to instability in the network.
By default, the active switch’s base MAC address is used as the root address of the VSS. This
root address does on change during SSO switchover so that an access-layer switch does see the
root change.
VSL EtherChannel
Since VSL EtherChannel uses LMP per member link, the link-aggregation protocols, such as
PAgP and LACP, are not required; each member link must be configured in unconditional
EtherChannel mode using the channelgroup group-number mode on command. Once the VSL
configuration is completed, using the switch convert mode virtual CLI command at the enable
prompt will start the conversion process. The conversion process includes changing the interface
naming convention from slot/interface to switch_number/slot/interface, saving the configuration,
and rebooting. During switch rebooting, the systems recognize the VSL configuration and
proceeds with their respective VSL ports initialization processes Trunking Configuration Best
Practices In a traditional multilayer design featuring standalone switches, when Dynamic Trunking
Protocol (DTP) and 802.1Q or Inter-Switch Link (ISL) negotiation are enabled, considerable time
can be spent negotiating trunk settings when a node or interface is restored. During negotiation,
traffic is dropped because the link is operational from a Layer-2 perspective. Up to two seconds
can be lost depending on where the trunk interface is being brought up.
However, in this configuration, DTP is not actively monitoring the state of the trunk and a
misconfigured trunk is not easily identified. There is a balance between fast convergence and your
ability to manage your configuration and change control.
In VSS, trunk mode of a port-channel interface being either desirable or undesirable does not
exhibit the behavior of standalone node. In VSS, each access-layer is connected via port-channel
(MEC), where a link member when brought on line is not a separate negotiation; rather it is an
addition to EtherChannel group. The node-related restoration losses are also not an issue when
compared to a standalone dual- node design in which each node has a separate control plane that
negotiates a separate trunking event. As with VSS, when the node is restored, the link-up event is
an additional member link of the MEC and not a trunk interface VSS Virtual Switching System
(VSS) is a network virtualization technology that allows two physical Cisco Catalyst 6500 series
switches to act as a single logical virtual switch. The VSS increases operational efficiencies andscales bandwidth up to 1.4 Tb/s. This technology is very similar to StackWise technology
used with the Cisco Catalyst 3750 series product line, which enables switches stacked together to
operate as one and use a single command-line interface (CLI) for management. However, VSS is
limited to two physical chassis connected together.
vPC
Virtual Port Channel (vPC) technology works by combining two Cisco Nexus 7000 series switches
or two Cisco Nexus 5000 series switches with 10GE links, which are then represented to other
switches as a single logical switch for port channeling purposes. With vPC, the spanning-tree
topology appears loop- free, although multiple redundant paths are present in the physical
topology.
RFC 4318
This memo defines an SMIv2 MIB module for managing the Rapid Spanning Tree capability
defined by the IEEE P802.1t and P802.1w amendments to IEEE Standard 802.1D-1998 for
bridging between Local Area Network (LAN) segments. The objects in this MIB are defined to
apply both to transparent bridging and to bridges connected by subnetworks other than LAN
segments.Cisco CCDA Official Certification Guide Fourth Edition
VSS Enabled Campus Design
http://www.cisco.com/en/US/docs/solutions/Enterprise/Campus/VSS30dg/VSSdg_ch3.html#wpxref89818
Virtual Switching System (VSS) Q&A
http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps9336/prod_qas0900aecd806ed74b
.html
Cisco Catalyst 6500 Virtual Switching System Deployment Best Practices
http://www.cisco.com/en/US/products/ps9336/products_tech_note09186a0080a7c837.shtml
http://www.cisco.com/en/US/docs/solutions/Enterprise/Campus/VSS30dg/VSS-dg_ch3.html
http://www.cisco.com/en/US/docs/solutions/Enterprise/Campus/VSS30dg/VSSdg_ch3.html#wp1079784