Which of these statements is true concerning the data center access layer design?
A.
The access layer in the data center is typically built at Layer 3, which allows for better shaping of services across multiple servers.
B.
With Layer 2 access, the default gateway for the servers can be configured at the access or aggregation layer.
C.
A dual-homing NIC requires a VLAN or trunk between the two access switches to support the dual IP address on the two server links to two separate switches.
D.
The access layer is normally not required, as dual homing is standard from the servers to the aggregation layer.
Explanation:
With Layer 2 / 3, capabilities in-built access layer switches can have data & voice VLANs with interfaces; this is helpful in improving routing convergence.
Link:
http://www.cisco.com/application/pdf/en/us/guest/netsol/ns432/c649/ccmigration_09186a00805fcc bf.pdf
Answer B is wrong. With Layer 2 and 3 you can choose the Default Gateway for your servers to be in the Access Switches or in the Aggregation Switches.
With Layer 2 only, the Default Gateway must be in the Aggregation Layer.
Answer C is right. A Dual-homing NIC needs Layer 2 connectivity between the 2 interfaces so there must be either a trunk or a VLAN connected between the Access Switches.
Official Cert Guide P. 136 Other advantages of Layer 2 access are support for NIC teaming and server clustering that requires network connections to be Layer 2 adjacent or on the same VLAN with one another.
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@ Senior – Read the question again. I made the same mistake…. Dual NICs use only one IP Address (they can share the MAC address or have separate MAC Addresses depending on the drivers). (B) is strait out of the Certification guide.
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Hmm… Still, if you only have Layer 2 switches in the Access, you cannot define the Default Gateway for your servers there…
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Did we agree on a final answer?
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C is wrong because layer 2 adjacency can be established through aggregation layer
D is wrong too
B shouldn’t be a correct answer as default gateway is configured on aggregation layer (HSRP configuration)
I think A is the correct answer
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Foundation Lerning Guide
Page 206-207
Data Center Access Layer
The data center access layer provides Layer 2, Layer 3, and mainframe connectivity. The
design of the access layer varies depending on whether Layer 2 or Layer 3 access is used.
The access layer in the data center is typically built at Layer 2, which allows more efficient
sharing of service devices across multiple servers. It also allows the use of Layer 2 cluster-ing, which requires the servers to be Layer 2 adjacent. With Layer 2 access, the default
gateway for the servers can be configured at the access layer or the aggregation layer.
Data Center Access Layer
The data center access layer provides Layer 2, Layer 3, and mainframe connectivity. The
design of the access layer varies depending on whether Layer 2 or Layer 3 access is used.
The access layer in the data center is typically built at Layer 2, which allows more efficient
sharing of service devices across multiple servers. It also allows the use of Layer 2 cluster-ing, which requires the servers to be Layer 2 adjacent. With Layer 2 access, the default
gateway for the servers can be configured at the access layer or the aggregation layer.
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With a dual-homing NIC, a VLAN or trunk between the two access switches is required
to support the single IP address on the two server links to two separate switches. The
default gateway is implemented at the access layer as well.
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I’m sorry but im currently studying to achieving my CCDA, however how can be configured a gateway in the access layer 2? i really can’t understand how can be posible to do this.
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I think this a badly worded question.
D is clearly wrong – an access layer is required
C is wrong, as it uses multiple IPs’s
A would appear to be wrong, as servers generally require L2 adjacency in the data centre (for example, to implement vMotion)
B still looks to be the most right. The servers connect to the access layer at layer-2. L3 SVI’s are configured, and HSRP or VRRP is used, so the default gateway is at the access layer.
This question makes it sound like the default gateway is at layer-2, however the ‘Layer-2 access’ is for the servers.
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