Network Switches — 40 Frequently Asked Questions
Real questions enterprise IT engineers ask about Network Switches, with practical answers from Pro Disk Engineering. Questions sourced from Server Fault and Network Engineering Stack Exchange under CC BY-SA — see source links per question. Answers are original Pro Disk Network content with links to our buying guides and product catalog.
How do VLANs work?
Network switch questions usually involve topology, oversubscription, or protocol support.
VLAN basics: access port = untagged single VLAN, trunk port = multiple tagged VLANs. The 802.1Q header adds 4 bytes to the Ethernet frame. Modern data center fabrics replace flat VLANs with VXLAN overlays (BGP-EVPN) for scale beyond 4094 segments.
Pro Disk Network ships Cisco Catalyst, Arista, Juniper, HPE Aruba, and Extreme switches. Switch buying guide · Networking catalog
Original question on Server Fault (153 votes · 136,087 views) ›
What's the difference between a Layer 2 & Layer 3 switch
Network switch questions usually involve topology, oversubscription, or protocol support.
The answer depends on your specific platform, workload, and operational requirements. For environment-specific guidance, email sales@prodisknetwork.com with your server model and target configuration.
Pro Disk Network ships Cisco Catalyst, Arista, Juniper, HPE Aruba, and Extreme switches. Switch buying guide · Networking catalog
Original question on Server Fault (52 votes · 300,185 views) ›
How to find the port a device is connected to, based on IP, on a Cisco Catalyst switch
Network switch questions usually involve topology, oversubscription, or protocol support.
The answer depends on your specific platform, workload, and operational requirements. For environment-specific guidance, email sales@prodisknetwork.com with your server model and target configuration.
Pro Disk Network ships Cisco Catalyst, Arista, Juniper, HPE Aruba, and Extreme switches. Switch buying guide · Networking catalog
Original question on Network Engineering Stack Exchange (25 votes · 344,952 views) ›
Can you mount a network switch upside down?
Network switch questions usually involve topology, oversubscription, or protocol support.
The answer depends on your specific platform, workload, and operational requirements. For environment-specific guidance, email sales@prodisknetwork.com with your server model and target configuration.
Pro Disk Network ships Cisco Catalyst, Arista, Juniper, HPE Aruba, and Extreme switches. Switch buying guide · Networking catalog
Original question on Server Fault (115 votes · 16,751 views) ›
What is the difference between a managed and unmanaged switch?
Network switch questions usually involve topology, oversubscription, or protocol support.
The answer depends on your specific platform, workload, and operational requirements. For environment-specific guidance, email sales@prodisknetwork.com with your server model and target configuration.
Pro Disk Network ships Cisco Catalyst, Arista, Juniper, HPE Aruba, and Extreme switches. Switch buying guide · Networking catalog
Original question on Server Fault (68 votes · 109,570 views) ›
What happens when you plug two sides of a cable to a single networking device?
Network switch questions usually involve topology, oversubscription, or protocol support.
The answer depends on your specific platform, workload, and operational requirements. For environment-specific guidance, email sales@prodisknetwork.com with your server model and target configuration.
Pro Disk Network ships Cisco Catalyst, Arista, Juniper, HPE Aruba, and Extreme switches. Switch buying guide · Networking catalog
Original question on Server Fault (88 votes · 63,117 views) ›
Difference between control plane, data plane and management plane?
Network switch questions usually involve topology, oversubscription, or protocol support.
The answer depends on your specific platform, workload, and operational requirements. For environment-specific guidance, email sales@prodisknetwork.com with your server model and target configuration.
Pro Disk Network ships Cisco Catalyst, Arista, Juniper, HPE Aruba, and Extreme switches. Switch buying guide · Networking catalog
Original question on Network Engineering Stack Exchange (51 votes · 113,333 views) ›
What are the implications of having two subnets on the same switch?
Network switch questions usually involve topology, oversubscription, or protocol support.
VLAN basics: access port = untagged single VLAN, trunk port = multiple tagged VLANs. The 802.1Q header adds 4 bytes to the Ethernet frame. Modern data center fabrics replace flat VLANs with VXLAN overlays (BGP-EVPN) for scale beyond 4094 segments.
Pro Disk Network ships Cisco Catalyst, Arista, Juniper, HPE Aruba, and Extreme switches. Switch buying guide · Networking catalog
Original question on Server Fault (48 votes · 115,623 views) ›
How can I see which switchports are not in use?
Network switch questions usually involve topology, oversubscription, or protocol support.
The answer depends on your specific platform, workload, and operational requirements. For environment-specific guidance, email sales@prodisknetwork.com with your server model and target configuration.
Pro Disk Network ships Cisco Catalyst, Arista, Juniper, HPE Aruba, and Extreme switches. Switch buying guide · Networking catalog
Original question on Network Engineering Stack Exchange (50 votes · 106,758 views) ›
What is a patch panel?
Network switch questions usually involve topology, oversubscription, or protocol support.
The answer depends on your specific platform, workload, and operational requirements. For environment-specific guidance, email sales@prodisknetwork.com with your server model and target configuration.
Pro Disk Network ships Cisco Catalyst, Arista, Juniper, HPE Aruba, and Extreme switches. Switch buying guide · Networking catalog
Original question on Server Fault (36 votes · 104,187 views) ›
How can I diagnose a bridging (ethernet) loop?
Network switch questions usually involve topology, oversubscription, or protocol support.
STP / RSTP / MSTP: use RSTP (802.1w) over legacy STP for sub-second convergence. MSTP (802.1s) maps multiple VLANs to fewer spanning-tree instances. For modern leaf-spine fabrics, replace STP with BGP-EVPN underlay (no loop possible because no L2 forwarding between leaves).
Pro Disk Network ships Cisco Catalyst, Arista, Juniper, HPE Aruba, and Extreme switches. Switch buying guide · Networking catalog
Original question on Network Engineering Stack Exchange (45 votes · 85,137 views) ›
Using SNMP to retrieve the ARP and mac-address tables from a switch
Network switch questions usually involve topology, oversubscription, or protocol support.
The answer depends on your specific platform, workload, and operational requirements. For environment-specific guidance, email sales@prodisknetwork.com with your server model and target configuration.
Pro Disk Network ships Cisco Catalyst, Arista, Juniper, HPE Aruba, and Extreme switches. Switch buying guide · Networking catalog
Original question on Network Engineering Stack Exchange (34 votes · 96,549 views) ›
How does a switch learn a switch table?
Network switch questions usually involve topology, oversubscription, or protocol support.
The answer depends on your specific platform, workload, and operational requirements. For environment-specific guidance, email sales@prodisknetwork.com with your server model and target configuration.
Pro Disk Network ships Cisco Catalyst, Arista, Juniper, HPE Aruba, and Extreme switches. Switch buying guide · Networking catalog
Original question on Network Engineering Stack Exchange (30 votes · 76,805 views) ›
Does using a single cable to connect two switches create a bottleneck?
Network switch questions usually involve topology, oversubscription, or protocol support.
The answer depends on your specific platform, workload, and operational requirements. For environment-specific guidance, email sales@prodisknetwork.com with your server model and target configuration.
Pro Disk Network ships Cisco Catalyst, Arista, Juniper, HPE Aruba, and Extreme switches. Switch buying guide · Networking catalog
Original question on Server Fault (33 votes · 62,720 views) ›
What should I pay attention to when I'm buying a network switch?
Network switch questions usually involve topology, oversubscription, or protocol support.
The answer depends on your specific platform, workload, and operational requirements. For environment-specific guidance, email sales@prodisknetwork.com with your server model and target configuration.
Pro Disk Network ships Cisco Catalyst, Arista, Juniper, HPE Aruba, and Extreme switches. Switch buying guide · Networking catalog
Original question on Server Fault (58 votes · 9,531 views) ›
Bits per second vs. Packets per second
Network switch questions usually involve topology, oversubscription, or protocol support.
The answer depends on your specific platform, workload, and operational requirements. For environment-specific guidance, email sales@prodisknetwork.com with your server model and target configuration.
Pro Disk Network ships Cisco Catalyst, Arista, Juniper, HPE Aruba, and Extreme switches. Switch buying guide · Networking catalog
Original question on Network Engineering Stack Exchange (41 votes · 43,009 views) ›
What causes total output drops on a cisco switch interface?
Network switch questions usually involve topology, oversubscription, or protocol support.
The answer depends on your specific platform, workload, and operational requirements. For environment-specific guidance, email sales@prodisknetwork.com with your server model and target configuration.
Pro Disk Network ships Cisco Catalyst, Arista, Juniper, HPE Aruba, and Extreme switches. Switch buying guide · Networking catalog
Original question on Network Engineering Stack Exchange (17 votes · 88,072 views) ›
Why can't devices on different VLANs, but on the same subnet, communicate?
Network switch questions usually involve topology, oversubscription, or protocol support.
VLAN basics: access port = untagged single VLAN, trunk port = multiple tagged VLANs. The 802.1Q header adds 4 bytes to the Ethernet frame. Modern data center fabrics replace flat VLANs with VXLAN overlays (BGP-EVPN) for scale beyond 4094 segments.
Pro Disk Network ships Cisco Catalyst, Arista, Juniper, HPE Aruba, and Extreme switches. Switch buying guide · Networking catalog
Original question on Network Engineering Stack Exchange (27 votes · 33,898 views) ›
Accidentally Removed Allowed VLANs from Cisco Switch Dot1Q Trunk
Network switch questions usually involve topology, oversubscription, or protocol support.
VLAN basics: access port = untagged single VLAN, trunk port = multiple tagged VLANs. The 802.1Q header adds 4 bytes to the Ethernet frame. Modern data center fabrics replace flat VLANs with VXLAN overlays (BGP-EVPN) for scale beyond 4094 segments.
Pro Disk Network ships Cisco Catalyst, Arista, Juniper, HPE Aruba, and Extreme switches. Switch buying guide · Networking catalog
Original question on Network Engineering Stack Exchange (25 votes · 30,470 views) ›
What kind of network attack turns a switch into a hub?
Network switch questions usually involve topology, oversubscription, or protocol support.
The answer depends on your specific platform, workload, and operational requirements. For environment-specific guidance, email sales@prodisknetwork.com with your server model and target configuration.
Pro Disk Network ships Cisco Catalyst, Arista, Juniper, HPE Aruba, and Extreme switches. Switch buying guide · Networking catalog
Original question on Server Fault (36 votes · 8,274 views) ›
What does the 1000M on a network switch mean?
Network switch questions usually involve topology, oversubscription, or protocol support.
The answer depends on your specific platform, workload, and operational requirements. For environment-specific guidance, email sales@prodisknetwork.com with your server model and target configuration.
Pro Disk Network ships Cisco Catalyst, Arista, Juniper, HPE Aruba, and Extreme switches. Switch buying guide · Networking catalog
Original question on Network Engineering Stack Exchange (29 votes · 19,131 views) ›
Troubleshooting "Down BGP" connections
Network switch questions usually involve topology, oversubscription, or protocol support.
Routing protocol selection: BGP for inter-AS and modern data-center EVPN underlays. OSPF for internal enterprise routing. Static for branch sites. EIGRP is Cisco-specific and discouraged for new builds.
Pro Disk Network ships Cisco Catalyst, Arista, Juniper, HPE Aruba, and Extreme switches. Switch buying guide · Networking catalog
Original question on Network Engineering Stack Exchange (21 votes · 24,008 views) ›
Why is the CAM table in a switch called CAM table and not MAC table even though it holds MAC addresses?
Network switch questions usually involve topology, oversubscription, or protocol support.
The answer depends on your specific platform, workload, and operational requirements. For environment-specific guidance, email sales@prodisknetwork.com with your server model and target configuration.
Pro Disk Network ships Cisco Catalyst, Arista, Juniper, HPE Aruba, and Extreme switches. Switch buying guide · Networking catalog
Original question on Network Engineering Stack Exchange (22 votes · 20,049 views) ›
Can I use a Catalyst 2960-S for iSCSI?
Network switch questions usually involve topology, oversubscription, or protocol support.
iSCSI / FC LUN scanning: from Linux iscsiadm -m discovery + iscsiadm -m node --login; on Windows, refresh in iSCSI Initiator. Rescan SCSI bus with echo "- - -" > /sys/class/scsi_host/hostN/scan.
Pro Disk Network ships Cisco Catalyst, Arista, Juniper, HPE Aruba, and Extreme switches. Switch buying guide · Networking catalog
Original question on Network Engineering Stack Exchange (25 votes · 9,580 views) ›
Should portfast be used on a port potentially connecting to an unmanaged switch?
Network switch questions usually involve topology, oversubscription, or protocol support.
VLAN basics: access port = untagged single VLAN, trunk port = multiple tagged VLANs. The 802.1Q header adds 4 bytes to the Ethernet frame. Modern data center fabrics replace flat VLANs with VXLAN overlays (BGP-EVPN) for scale beyond 4094 segments.
STP / RSTP / MSTP: use RSTP (802.1w) over legacy STP for sub-second convergence. MSTP (802.1s) maps multiple VLANs to fewer spanning-tree instances. For modern leaf-spine fabrics, replace STP with BGP-EVPN underlay (no loop possible because no L2 forwarding between leaves).
Pro Disk Network ships Cisco Catalyst, Arista, Juniper, HPE Aruba, and Extreme switches. Switch buying guide · Networking catalog
Original question on Network Engineering Stack Exchange (19 votes · 19,079 views) ›
Building new network and need 200+ wireless devices
Network switch questions usually involve topology, oversubscription, or protocol support.
SMART monitoring: alert on attributes 187 (reported uncorrectable errors), 197 (current pending sector count), and 198 (offline uncorrectable count). Non-zero values typically indicate 30-90 days of remaining service life.
Pro Disk Network ships Cisco Catalyst, Arista, Juniper, HPE Aruba, and Extreme switches. Switch buying guide · Networking catalog
Original question on Network Engineering Stack Exchange (23 votes · 7,518 views) ›
What is the difference between all the switching modes on 6500/7600?
Network switch questions usually involve topology, oversubscription, or protocol support.
The answer depends on your specific platform, workload, and operational requirements. For environment-specific guidance, email sales@prodisknetwork.com with your server model and target configuration.
Pro Disk Network ships Cisco Catalyst, Arista, Juniper, HPE Aruba, and Extreme switches. Switch buying guide · Networking catalog
Original question on Network Engineering Stack Exchange (20 votes · 4,086 views) ›
ASICs vs x86 general-purpose routing/switching
Network switch questions usually involve topology, oversubscription, or protocol support.
The answer depends on your specific platform, workload, and operational requirements. For environment-specific guidance, email sales@prodisknetwork.com with your server model and target configuration.
Pro Disk Network ships Cisco Catalyst, Arista, Juniper, HPE Aruba, and Extreme switches. Switch buying guide · Networking catalog
Original question on Network Engineering Stack Exchange (16 votes · 11,677 views) ›
What happens when 2 computers transmits at the same time to a 3rd one in a full duplex switch?
Network switch questions usually involve topology, oversubscription, or protocol support.
VLAN basics: access port = untagged single VLAN, trunk port = multiple tagged VLANs. The 802.1Q header adds 4 bytes to the Ethernet frame. Modern data center fabrics replace flat VLANs with VXLAN overlays (BGP-EVPN) for scale beyond 4094 segments.
Pro Disk Network ships Cisco Catalyst, Arista, Juniper, HPE Aruba, and Extreme switches. Switch buying guide · Networking catalog
Original question on Network Engineering Stack Exchange (16 votes · 5,741 views) ›
Configure Cisco ASA in Transparent mode: Layer2 DMZ w/ Vlan translation
Network switch questions usually involve topology, oversubscription, or protocol support.
VLAN basics: access port = untagged single VLAN, trunk port = multiple tagged VLANs. The 802.1Q header adds 4 bytes to the Ethernet frame. Modern data center fabrics replace flat VLANs with VXLAN overlays (BGP-EVPN) for scale beyond 4094 segments.
Pro Disk Network ships Cisco Catalyst, Arista, Juniper, HPE Aruba, and Extreme switches. Switch buying guide · Networking catalog
Original question on Network Engineering Stack Exchange (15 votes · 7,173 views) ›
How to encapsulate all VLAN traffic inside VXLAN
Network switch questions usually involve topology, oversubscription, or protocol support.
VLAN basics: access port = untagged single VLAN, trunk port = multiple tagged VLANs. The 802.1Q header adds 4 bytes to the Ethernet frame. Modern data center fabrics replace flat VLANs with VXLAN overlays (BGP-EVPN) for scale beyond 4094 segments.
Pro Disk Network ships Cisco Catalyst, Arista, Juniper, HPE Aruba, and Extreme switches. Switch buying guide · Networking catalog
Original question on Network Engineering Stack Exchange (5 votes · 11,142 views) ›
Arista MLAG ISSU upgrade - primary/secondary switch?
Network switch questions usually involve topology, oversubscription, or protocol support.
The answer depends on your specific platform, workload, and operational requirements. For environment-specific guidance, email sales@prodisknetwork.com with your server model and target configuration.
Pro Disk Network ships Cisco Catalyst, Arista, Juniper, HPE Aruba, and Extreme switches. Switch buying guide · Networking catalog
Original question on Network Engineering Stack Exchange (8 votes · 5,062 views) ›
Unlock 3rd party transceivers on Arista switches
Network switch questions usually involve topology, oversubscription, or protocol support.
Transceiver selection: DAC for 1-7m, AOC for 7-30m, SR optics on MMF up to 100m, LR optics on SMF up to 10km. Vendor coding matters — Cisco-coded optics avoid "service unsupported-transceiver" warnings on IOS / NX-OS.
Pro Disk Network ships Cisco Catalyst, Arista, Juniper, HPE Aruba, and Extreme switches. Switch buying guide · Networking catalog
Original question on Network Engineering Stack Exchange (4 votes · 12,825 views) ›
NX-OS 9.3: ECMP polarization and "ip load-sharing ... rotate"
Network switch questions usually involve topology, oversubscription, or protocol support.
The answer depends on your specific platform, workload, and operational requirements. For environment-specific guidance, email sales@prodisknetwork.com with your server model and target configuration.
Pro Disk Network ships Cisco Catalyst, Arista, Juniper, HPE Aruba, and Extreme switches. Switch buying guide · Networking catalog
Original question on Network Engineering Stack Exchange (6 votes · 4,184 views) ›
Can Cisco Nexus 3232C's SFP+ 1/33 and 1/34 ports use 1G optics?
Network switch questions usually involve topology, oversubscription, or protocol support.
VLAN basics: access port = untagged single VLAN, trunk port = multiple tagged VLANs. The 802.1Q header adds 4 bytes to the Ethernet frame. Modern data center fabrics replace flat VLANs with VXLAN overlays (BGP-EVPN) for scale beyond 4094 segments.
Transceiver selection: DAC for 1-7m, AOC for 7-30m, SR optics on MMF up to 100m, LR optics on SMF up to 10km. Vendor coding matters — Cisco-coded optics avoid "service unsupported-transceiver" warnings on IOS / NX-OS.
Pro Disk Network ships Cisco Catalyst, Arista, Juniper, HPE Aruba, and Extreme switches. Switch buying guide · Networking catalog
Original question on Network Engineering Stack Exchange (7 votes · 368 views) ›
Cisco NX-OS 9K - LDAP Configuration
Network switch questions usually involve topology, oversubscription, or protocol support.
HBA firmware mode: IT-mode (pass-through) is required for software RAID (ZFS, vSAN, Ceph). RAID-mode for hardware RAID. LSI/Broadcom 9300/9400/9500 series HBAs flash between modes cleanly.
Pro Disk Network ships Cisco Catalyst, Arista, Juniper, HPE Aruba, and Extreme switches. Switch buying guide · Networking catalog
Original question on Network Engineering Stack Exchange (6 votes · 2,164 views) ›
How can I upgrade Cisco Nexus switch if not enough space for new image?
Network switch questions usually involve topology, oversubscription, or protocol support.
The answer depends on your specific platform, workload, and operational requirements. For environment-specific guidance, email sales@prodisknetwork.com with your server model and target configuration.
Pro Disk Network ships Cisco Catalyst, Arista, Juniper, HPE Aruba, and Extreme switches. Switch buying guide · Networking catalog
Original question on Network Engineering Stack Exchange (4 votes · 4,985 views) ›
Cisco Nexus 9300 TCAM carving
Network switch questions usually involve topology, oversubscription, or protocol support.
HBA firmware mode: IT-mode (pass-through) is required for software RAID (ZFS, vSAN, Ceph). RAID-mode for hardware RAID. LSI/Broadcom 9300/9400/9500 series HBAs flash between modes cleanly.
Pro Disk Network ships Cisco Catalyst, Arista, Juniper, HPE Aruba, and Extreme switches. Switch buying guide · Networking catalog
Original question on Network Engineering Stack Exchange (4 votes · 4,359 views) ›
Nexus 3172T MTU
Network switch questions usually involve topology, oversubscription, or protocol support.
VLAN basics: access port = untagged single VLAN, trunk port = multiple tagged VLANs. The 802.1Q header adds 4 bytes to the Ethernet frame. Modern data center fabrics replace flat VLANs with VXLAN overlays (BGP-EVPN) for scale beyond 4094 segments.
Pro Disk Network ships Cisco Catalyst, Arista, Juniper, HPE Aruba, and Extreme switches. Switch buying guide · Networking catalog
Original question on Network Engineering Stack Exchange (4 votes · 4,241 views) ›
How to resolve a spanning tree issue on a server trunk port?
Network switch questions usually involve topology, oversubscription, or protocol support.
VLAN basics: access port = untagged single VLAN, trunk port = multiple tagged VLANs. The 802.1Q header adds 4 bytes to the Ethernet frame. Modern data center fabrics replace flat VLANs with VXLAN overlays (BGP-EVPN) for scale beyond 4094 segments.
STP / RSTP / MSTP: use RSTP (802.1w) over legacy STP for sub-second convergence. MSTP (802.1s) maps multiple VLANs to fewer spanning-tree instances. For modern leaf-spine fabrics, replace STP with BGP-EVPN underlay (no loop possible because no L2 forwarding between leaves).
Pro Disk Network ships Cisco Catalyst, Arista, Juniper, HPE Aruba, and Extreme switches. Switch buying guide · Networking catalog
Original question on Network Engineering Stack Exchange (5 votes · 1,804 views) ›
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