Today is mother’s day. Every single mother in the world dersers to be respected and loved. I love my mum so much that I bought Listerine for her.

Today;s topic is significant for our network since we are talking about high availability in layer2 switch. I also wanna touch a little about spanning tree protocol but that would be when I can figure the advanced version out.

There are several ways we can work on it.

  • Network Design
  • Etherchannel on Cisco Switch
  • First-Hop Redundancy protocol(FHRP)
  • Supervisor redundancy
  • Virtualization

Nothing explains better than visual picture: cisco three-layers First, what is a network design? This is when we talk about Cisco three-layered hierarchy #Core Layer

  • Low latency for traffic
  • Redundancy tolerance
  • High speed
  • Simplicity and Efficiency

And then it would be Distribution Layer, the job of which is to connect Core layer and Access layer

As we all know the job of access layer. It is the direct connectivity to the end users, layer2 switching, stp operations, PoE, Port-base Security, Dynamic arp inspection.

Aggregating switch links with Etherchannel

Make sure all ports participating in Etherchannel have the same configuration

  • Duplex
  • Speed
  • Native VLAN
  • Allowed VLANs
  • Switchport mode(access/trunk)

The interface can be configured into three modes like On, Auto, Desirable. While desirable interface will actively ask the other side to become an ehtercha nel while auto guy just wait passively for the other side.

Lets do a small experiment on GNS3. etherchannel

Switch(config)#interface range gi0/0 - 1
Switch(config-if-range)#channel-group 1 mode desirable

Hot Standby Router Protocol(HSRP) another hsrp

sw2(config-if)#int vlan 10
sw2(config-if)#standby 10 ip 172.31.10.254
sw2(config-if)#standby 10 priority 110 #default 100
sw2(config-if)#standby 10 preempt

When you finish the configuration, you can just show standby. In our case, we set switch 2 as the active switch for vlan 10 and the rest are just standby switch. We can also trigger the failover based on somehing like interface goes down

SW1(config)#int vlan 10
SW1(config-if)#standby 10 track 1 decrement 11
SW1(config-if)#standby 10 track 2 decrement 11 
SW1(config)#track 1 interface gigabitEthernet 1/2 line-protocol
SW1(config-track)#exit
SW1(config)#track 2 interface gigabitEthernet 2/1 line-protocol
SW1(config-track)#end

Gateway Load Balancing Protocol

This protocol is better because we wont only have one virtual gateway but four virtual mac-address and we can distribute the traffic as we can. We can have one Active Virtual Gateway and several Active Virtual Forwarder. But only AVG listens to ARP request for the virtual ip address.

Configuration

R1(config)#interface gigabitEthernet 0/0
R1(config-if)#glbp 8 ip 192.168.8.254

Advance load balancing configuration

R1(config)#interface gigabitEthernet 0/0
R1(config-if)#glbp 8 load-balancing weighted 
R1(config-if)#glbp 8 weighting 15

We usually do not have redundancy in access layer.