Last Updated on August 2, 2021 by Admin 2
You are configuring a vPC domain on SwitchA, SwitchB, and SwitchC. You connect all three switches by using 10-Gbps Ethernet ports. Next, you issue the following commands on each switch, in order:
vpc domain 101
You now want to configure the peer keepalive links between the switches.
Which of the following is true?
- You will not be able to peer any of the switches.
- You can peer all three switches if you add a vPC domain ID to SwitchB.
- You will be able to peer only two of the three switches.
- You can peer all three switches if you change the vPC domain ID.
You will be able to peer only two of the three switches in this scenario because it is not possible to configure more than two switches per virtual port channel (vPC) domain. A vPC domain is comprised of two switches per domain. Each switch in the vPC domain must be configured with the same vPC domain ID. To enable vPC configuration on a Cisco Nexus 7000 Series switch, you should issue the feature vpc command on both switches. To assign the vPC domain ID, you should issue the vpc domain domain-id command, where domain-id is an integer in the range from 1 through 1000, in global configuration mode. For example, issuing the vpc domain 101 command on a Cisco Nexus 7000 Series switch configures the switch with a vPC domain ID of 101.
A vPC forms an Open Systems Interconnection (OST) networking model Layer 2 port channel. Each virtual device context (VDC) is a separate switch in a vPC domain. A VDC logically virtualizes a switch. A VDC is a single virtual instance of physical switch hardware. A vPC logically combines ports from multiple switches into a single port-channel bundle. Conventional port channels, which are typically used to create high-bandwidth trunk links between two switches, require that all members of the bundle exist on the same switch. vPCs enable virtual domains that are comprised of multiple physical switches to connect as a single entity to a fabric extender, server, or other device.
Only one vPC domain can be configured per switch. If you were to issue more than one vpc domain domain-id command on a Cisco Nexus 7000 Series switch, the vPC domain ID of the switch would become whatever value was issued last. After you issue the vpc domain domain-id command, the switch is placed into vPC domain configuration mode. In vPC domain configuration mode, you should configure a peer keepalive link.
Peer keepalive links monitor the remote device to ensure that it is operational. You can configure a peer keepalive link in any virtual routing and forwarding (VRF) instance on the switch. Each switch must use its own Internet Protocol (IP) address as the peer keepalive link source IP address and the remote switch’s IP address as the peer keepalive link destination IP address. The following commands configure a peer keepalive link between SwitchA and SwitchB in vPC domain 101:
SwitchA(config)#vpc domain 101 SwitchA(config-vpc-domain)#peer-keepalive destination 192.168.1.2 source 192.168.1.1 vrf default SwitchB(config)#vpc domain 101 SwitchB(config-vpc-domain)#peer-keepalive destination 192.168.1.1 source 192.168.1.2 vrf default
A vPC peer link should always be a 10-gigabit-per-second (Gbps) Ethernet port. Peer links are configured as a port channel between the two members of the vPC domain. You should configure vPC peer links after you have successfully configured a peer keepalive link. Cisco recommends connecting two 10-Gbps Ethernet ports from two different input/output (I/O) modules. To configure a peer link, you should issue the vpc peer-link command in interface configuration mode. For example, the following commands configure a peer link on Port-channel 1:
SwitchA(config)#interface port-channel 1 SwitchA(config-if)#switchport mode trunk SwitchA(config-if)#vpc peer-link SwitchB(config)#interface port-channel 1 SwitchB(config-if)#switchport mode trunk SwitchB(config-if)#vpc peer-link
It is important to issue the correct channel-group commands on a port channel’s member ports prior to configuring the port channel. For example, if you are creating Port-channel 1 by using the Ethernet 2/1 and Ethernet 2/2 interfaces, you could issue the following commands on each switch to correctly configure those interfaces as members of the port channel:
SwitchA(config)#interface range ethernet 2/1-2 Switch(config-if-range)#switchport SwitchA(config-if-range)#channel-group 1 mode active SwitchB(config)#interface range ethernet 2/1-2 SwitchB(config-if-range)#switchport SwitchB(config-if-range)#channel-group 1 mode active