Access/Aggregation & Core layer

Popeye_Wang · Created Sep 29, 2020 11:37:31

Hello,

The following table lists the comparison between deploy gateway at the access layer and the aggregation layer.

	Gateways are deployed at the access layer.	Gateways are deployed at the aggregation layer.
Cost	Layer 3 switches are required at the access layer.The cost of a Layer 3 switch is higher than that of a Layer 2 switch. When a large number of access switches are required on the network The cost will be greatly increased.	Access switches use only Layer 2 switching. The cost is low.
Routing control	Layer 3 routing can be controlled through routing policies and policy-based routing. Different services can be transmitted on different links.	Layer 2 routing on access switches depends on the Layer 2 loop prevention technology, which is difficult to control.
Link efficiency	Load balancing is performed based on routes. Multiple uplinks are available for the same service on an access switch. When a switch is connected to different broadcast domains, only the local switch needs to forward packets, improving link efficiency.	Load balancing is implemented based on MSTP instances. Only one uplink is available for services in the same VLAN on an access switch. To implement communication between different broadcast domains on the same switch, aggregation switch Layer 3 forwarding is required. The link efficiency is low.
Redundancy	The implementation is complex. Access switches need to be stacked, and hosts need to use two NICs to connect to two switches.	The implementation is simple. VRRP is used to implement gateway redundancy.
broadcast domain	The broadcast domain is controlled by a single access switch and is small. Reduces link bandwidth and device performance consumption because the flooding scope of received unknown unicast, broadcast, and multicast frames is small. This mode is more secure. If an ARP attack occurs on the network, the impact scope is small. However, when a host is migrated to another access switch, IP address parameters need to be modified.	A broadcast domain can cover multiple access switches. A broadcast domain is large and has poor security. If an ARP attack occurs on the network, the impact scope is large. However, when the host is migrated to another access switch in the same broadcast domain, the IP address parameters do not need to be modified.
Maintenance	Routing protocols need to run between the access layer and the aggregation layer. Therefore, the network architecture is complex and difficult to maintain (complex routing protocols and route selection control policies need to be maintained).	No routing protocol is required between the access layer and the aggregation layer. Only the STP protocol needs to be enabled. The network architecture is simple and maintenance is easy.

The gateways of the campus network and office network are generally deployed at the aggregation layer (distributed and easy to expand and migrate). The gateways of the data center and the production network (confidential network) are generally deployed on the access network (centralized, low risk, and high security).

Gustavo.HdezF · Created Sep 23, 2020 20:01:54

Hello User.

In the medium to large networks, the modular design is usually used to split network functions. To ensure network flexibility and scalability within each module, the hierarchical architecture is generally used.

Traditional networks contain the core, aggregation, and access layers. The core layer provides high-speed data channels, the aggregation layer converges traffic and controls policies and the access layer offers various access modes to the terminals or host of the network.

In this case, it is preferentially to locate the DHCP server in the aggregation layer in that way your hosts can ask for an IP in a single point instead of having different DHCP servers in the access layer. The core layer is not recommended to have a DHCP server.

I hope this response to your question and any additional doubts just let us know.

Regards.

Gustavo.HdezF · Created Sep 23, 2020 19:40:18

Hello User. we are reviewing your question and we will answer you shortly. Thanks.

Gustavo.HdezF · Created Sep 23, 2020 20:01:54

Hello User.

In the medium to large networks, the modular design is usually used to split network functions. To ensure network flexibility and scalability within each module, the hierarchical architecture is generally used.

Traditional networks contain the core, aggregation, and access layers. The core layer provides high-speed data channels, the aggregation layer converges traffic and controls policies and the access layer offers various access modes to the terminals or host of the network.

In this case, it is preferentially to locate the DHCP server in the aggregation layer in that way your hosts can ask for an IP in a single point instead of having different DHCP servers in the access layer. The core layer is not recommended to have a DHCP server.

I hope this response to your question and any additional doubts just let us know.

Regards.

Popeye_Wang · Created Sep 29, 2020 11:37:31

Hello,

The following table lists the comparison between deploy gateway at the access layer and the aggregation layer.

	Gateways are deployed at the access layer.	Gateways are deployed at the aggregation layer.
Cost	Layer 3 switches are required at the access layer.The cost of a Layer 3 switch is higher than that of a Layer 2 switch. When a large number of access switches are required on the network The cost will be greatly increased.	Access switches use only Layer 2 switching. The cost is low.
Routing control	Layer 3 routing can be controlled through routing policies and policy-based routing. Different services can be transmitted on different links.	Layer 2 routing on access switches depends on the Layer 2 loop prevention technology, which is difficult to control.
Link efficiency	Load balancing is performed based on routes. Multiple uplinks are available for the same service on an access switch. When a switch is connected to different broadcast domains, only the local switch needs to forward packets, improving link efficiency.	Load balancing is implemented based on MSTP instances. Only one uplink is available for services in the same VLAN on an access switch. To implement communication between different broadcast domains on the same switch, aggregation switch Layer 3 forwarding is required. The link efficiency is low.
Redundancy	The implementation is complex. Access switches need to be stacked, and hosts need to use two NICs to connect to two switches.	The implementation is simple. VRRP is used to implement gateway redundancy.
broadcast domain	The broadcast domain is controlled by a single access switch and is small. Reduces link bandwidth and device performance consumption because the flooding scope of received unknown unicast, broadcast, and multicast frames is small. This mode is more secure. If an ARP attack occurs on the network, the impact scope is small. However, when a host is migrated to another access switch, IP address parameters need to be modified.	A broadcast domain can cover multiple access switches. A broadcast domain is large and has poor security. If an ARP attack occurs on the network, the impact scope is large. However, when the host is migrated to another access switch in the same broadcast domain, the IP address parameters do not need to be modified.
Maintenance	Routing protocols need to run between the access layer and the aggregation layer. Therefore, the network architecture is complex and difficult to maintain (complex routing protocols and route selection control policies need to be maintained).	No routing protocol is required between the access layer and the aggregation layer. Only the STP protocol needs to be enabled. The network architecture is simple and maintenance is easy.

The gateways of the campus network and office network are generally deployed at the aggregation layer (distributed and easy to expand and migrate). The gateways of the data center and the production network (confidential network) are generally deployed on the access network (centralized, low risk, and high security).

DawoodShah · Created Nov 9, 2020 09:48:21

Thanks this is helpful

Amrabdullah · Created Jan 20, 2021 14:44:50

thanks

Access/Aggregation & Core layer

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