Cisco — 30 Real Engineering Questions
Real questions enterprise IT engineers ask about Cisco hardware, sourced from Server Fault and Network Engineering Stack Exchange under CC BY-SA. Answers are original Pro Disk Network content with internal links to our Cisco catalog and buying guides.
How to find the port a device is connected to, based on IP, on a Cisco Catalyst switch
This is a common operational question for Cisco environments.
For environment-specific guidance on this question, email sales@prodisknetwork.com with your server model and details.
Pro Disk Network ships Cisco Catalyst, Nexus switches and UCS servers, plus pre-coded Cisco-compatible transceivers. Cisco catalog · Buying guides
Original question on Network Engineering Stack Exchange (25 votes · 344,952 views) ›
64-bit Cisco VPN client (IPsec)?
This is a common operational question for Cisco environments.
For environment-specific guidance on this question, email sales@prodisknetwork.com with your server model and details.
Pro Disk Network ships Cisco Catalyst, Nexus switches and UCS servers, plus pre-coded Cisco-compatible transceivers. Cisco catalog · Buying guides
Original question on Server Fault (47 votes · 126,966 views) ›
Difference between control plane, data plane and management plane?
This is a common operational question for Cisco environments.
For environment-specific guidance on this question, email sales@prodisknetwork.com with your server model and details.
Pro Disk Network ships Cisco Catalyst, Nexus switches and UCS servers, plus pre-coded Cisco-compatible transceivers. Cisco catalog · Buying guides
Original question on Network Engineering Stack Exchange (51 votes · 113,333 views) ›
How can I see which switchports are not in use?
This is a common operational question for Cisco environments.
For environment-specific guidance on this question, email sales@prodisknetwork.com with your server model and details.
Pro Disk Network ships Cisco Catalyst, Nexus switches and UCS servers, plus pre-coded Cisco-compatible transceivers. Cisco catalog · Buying guides
Original question on Network Engineering Stack Exchange (50 votes · 106,758 views) ›
How can I capture traffic on Cisco IOS switches?
This is a common operational question for Cisco environments.
For environment-specific guidance on this question, email sales@prodisknetwork.com with your server model and details.
Pro Disk Network ships Cisco Catalyst, Nexus switches and UCS servers, plus pre-coded Cisco-compatible transceivers. Cisco catalog · Buying guides
Original question on Network Engineering Stack Exchange (27 votes · 119,005 views) ›
Using SNMP to retrieve the ARP and mac-address tables from a switch
This is a common operational question for Cisco environments.
For environment-specific guidance on this question, email sales@prodisknetwork.com with your server model and details.
Pro Disk Network ships Cisco Catalyst, Nexus switches and UCS servers, plus pre-coded Cisco-compatible transceivers. Cisco catalog · Buying guides
Original question on Network Engineering Stack Exchange (34 votes · 96,549 views) ›
Cisco Anyconnect: Vpn establishment capability from a remote desktop is disabled
This is a common operational question for Cisco environments.
For environment-specific guidance on this question, email sales@prodisknetwork.com with your server model and details.
Pro Disk Network ships Cisco Catalyst, Nexus switches and UCS servers, plus pre-coded Cisco-compatible transceivers. Cisco catalog · Buying guides
Original question on Server Fault (19 votes · 94,635 views) ›
How can I force VTP clients to update their VLAN database from the VTP server, on Cisco devices?
This is a common operational question for Cisco environments.
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, Nexus switches and UCS servers, plus pre-coded Cisco-compatible transceivers. Cisco catalog · Buying guides
Original question on Network Engineering Stack Exchange (24 votes · 74,171 views) ›
What causes total output drops on a cisco switch interface?
This is a common operational question for Cisco environments.
For environment-specific guidance on this question, email sales@prodisknetwork.com with your server model and details.
Pro Disk Network ships Cisco Catalyst, Nexus switches and UCS servers, plus pre-coded Cisco-compatible transceivers. Cisco catalog · Buying guides
Original question on Network Engineering Stack Exchange (17 votes · 88,072 views) ›
Identify machines connected to switch
This is a common operational question for Cisco environments.
For environment-specific guidance on this question, email sales@prodisknetwork.com with your server model and details.
Pro Disk Network ships Cisco Catalyst, Nexus switches and UCS servers, plus pre-coded Cisco-compatible transceivers. Cisco catalog · Buying guides
Original question on Server Fault (13 votes · 95,763 views) ›
ARP broadcast flooding network and high cpu usage
This is a common operational question for Cisco environments.
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.
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, Nexus switches and UCS servers, plus pre-coded Cisco-compatible transceivers. Cisco catalog · Buying guides
Original question on Server Fault (20 votes · 77,899 views) ›
What is the meaning of the CRC counter on a cisco device?
This is a common operational question for Cisco environments.
For environment-specific guidance on this question, email sales@prodisknetwork.com with your server model and details.
Pro Disk Network ships Cisco Catalyst, Nexus switches and UCS servers, plus pre-coded Cisco-compatible transceivers. Cisco catalog · Buying guides
Original question on Network Engineering Stack Exchange (30 votes · 57,504 views) ›
Protocols: EIGRP vs OSPF
This is a common operational question for Cisco environments.
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, Nexus switches and UCS servers, plus pre-coded Cisco-compatible transceivers. Cisco catalog · Buying guides
Original question on Network Engineering Stack Exchange (23 votes · 62,362 views) ›
What is "oversubscription" in Networking?
This is a common operational question for Cisco environments.
For environment-specific guidance on this question, email sales@prodisknetwork.com with your server model and details.
Pro Disk Network ships Cisco Catalyst, Nexus switches and UCS servers, plus pre-coded Cisco-compatible transceivers. Cisco catalog · Buying guides
Original question on Network Engineering Stack Exchange (36 votes · 30,883 views) ›
Cisco AnyConnect SSL VPN client allows local LAN access, but not on additional multi-homed server
This is a common operational question for Cisco environments.
For environment-specific guidance on this question, email sales@prodisknetwork.com with your server model and details.
Pro Disk Network ships Cisco Catalyst, Nexus switches and UCS servers, plus pre-coded Cisco-compatible transceivers. Cisco catalog · Buying guides
Original question on Server Fault (23 votes · 44,580 views) ›
Difference between access list and prefix list?
This is a common operational question for Cisco environments.
For environment-specific guidance on this question, email sales@prodisknetwork.com with your server model and details.
Pro Disk Network ships Cisco Catalyst, Nexus switches and UCS servers, plus pre-coded Cisco-compatible transceivers. Cisco catalog · Buying guides
Original question on Network Engineering Stack Exchange (24 votes · 41,614 views) ›
Code to generate Cisco "secret" password hashes?
This is a common operational question for Cisco environments.
For environment-specific guidance on this question, email sales@prodisknetwork.com with your server model and details.
Pro Disk Network ships Cisco Catalyst, Nexus switches and UCS servers, plus pre-coded Cisco-compatible transceivers. Cisco catalog · Buying guides
Original question on Server Fault (15 votes · 57,084 views) ›
Accidentally Removed Allowed VLANs from Cisco Switch Dot1Q Trunk
This is a common operational question for Cisco environments.
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, Nexus switches and UCS servers, plus pre-coded Cisco-compatible transceivers. Cisco catalog · Buying guides
Original question on Network Engineering Stack Exchange (25 votes · 30,470 views) ›
Troubleshooting "Down BGP" connections
This is a common operational question for Cisco environments.
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, Nexus switches and UCS servers, plus pre-coded Cisco-compatible transceivers. Cisco catalog · Buying guides
Original question on Network Engineering Stack Exchange (21 votes · 24,008 views) ›
Can I use a Catalyst 2960-S for iSCSI?
This is a common operational question for Cisco environments.
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, Nexus switches and UCS servers, plus pre-coded Cisco-compatible transceivers. Cisco catalog · Buying guides
Original question on Network Engineering Stack Exchange (25 votes · 9,580 views) ›
How can I verify QoS DSCP marking on a Cisco Catalyst 4500E?
This is a common operational question for Cisco environments.
For environment-specific guidance on this question, email sales@prodisknetwork.com with your server model and details.
Pro Disk Network ships Cisco Catalyst, Nexus switches and UCS servers, plus pre-coded Cisco-compatible transceivers. Cisco catalog · Buying guides
Original question on Network Engineering Stack Exchange (13 votes · 23,533 views) ›
All WiFi clients losing connectivity at the same time
This is a common operational question for Cisco environments.
Linux memory accounting: RSS = physical RAM in use, VIRT = virtual address space (includes mapped files), PSS = proportional shared pages. The "available" column in free already accounts for reclaimable cache — use that as your real free-RAM number.
Pro Disk Network ships Cisco Catalyst, Nexus switches and UCS servers, plus pre-coded Cisco-compatible transceivers. Cisco catalog · Buying guides
Original question on Network Engineering Stack Exchange (22 votes · 1,828 views) ›
What is the difference between all the switching modes on 6500/7600?
This is a common operational question for Cisco environments.
For environment-specific guidance on this question, email sales@prodisknetwork.com with your server model and details.
Pro Disk Network ships Cisco Catalyst, Nexus switches and UCS servers, plus pre-coded Cisco-compatible transceivers. Cisco catalog · Buying guides
Original question on Network Engineering Stack Exchange (20 votes · 4,086 views) ›
ASICs vs x86 general-purpose routing/switching
This is a common operational question for Cisco environments.
For environment-specific guidance on this question, email sales@prodisknetwork.com with your server model and details.
Pro Disk Network ships Cisco Catalyst, Nexus switches and UCS servers, plus pre-coded Cisco-compatible transceivers. Cisco catalog · Buying guides
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?
This is a common operational question for Cisco environments.
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, Nexus switches and UCS servers, plus pre-coded Cisco-compatible transceivers. Cisco catalog · Buying guides
Original question on Network Engineering Stack Exchange (16 votes · 5,741 views) ›
Configure Cisco ASA in Transparent mode: Layer2 DMZ w/ Vlan translation
This is a common operational question for Cisco environments.
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, Nexus switches and UCS servers, plus pre-coded Cisco-compatible transceivers. Cisco catalog · Buying guides
Original question on Network Engineering Stack Exchange (15 votes · 7,173 views) ›
IPv6: How to start? (ISP perspective)
This is a common operational question for Cisco environments.
For environment-specific guidance on this question, email sales@prodisknetwork.com with your server model and details.
Pro Disk Network ships Cisco Catalyst, Nexus switches and UCS servers, plus pre-coded Cisco-compatible transceivers. Cisco catalog · Buying guides
Original question on Server Fault (17 votes · 1,656 views) ›
Are Cisco admins expected to understand classful networks?
This is a common operational question for Cisco environments.
For environment-specific guidance on this question, email sales@prodisknetwork.com with your server model and details.
Pro Disk Network ships Cisco Catalyst, Nexus switches and UCS servers, plus pre-coded Cisco-compatible transceivers. Cisco catalog · Buying guides
Original question on Server Fault (16 votes · 3,475 views) ›
Translating SNMPWALK output into human-readable format
This is a common operational question for Cisco environments.
For environment-specific guidance on this question, email sales@prodisknetwork.com with your server model and details.
Pro Disk Network ships Cisco Catalyst, Nexus switches and UCS servers, plus pre-coded Cisco-compatible transceivers. Cisco catalog · Buying guides
Original question on Network Engineering Stack Exchange (12 votes · 8,746 views) ›
Do I really need a DB9-RJ45 adapter to connect to a Cisco router console, and if so, why?
This is a common operational question for Cisco environments.
For environment-specific guidance on this question, email sales@prodisknetwork.com with your server model and details.
Pro Disk Network ships Cisco Catalyst, Nexus switches and UCS servers, plus pre-coded Cisco-compatible transceivers. Cisco catalog · Buying guides
Original question on Server Fault (13 votes · 6,194 views) ›
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