🎤 CCNP Data Center — Interview Q&A

❓ Data centers 3-tier سے spine-leaf کی طرف کیوں گئے؟Data centers 3-tier se spine-leaf ki taraf kyun gaye?Why did data centers move from 3-tier to spine-leaf?

3-tier میں سرور ٹریفک چار hops سے گزرتا ہے (access → aggregation → core → aggregation → access)۔ Spine-leaf میں ہر leaf ہر spine سے جڑا ہے، اس لیے ہمیشہ دو hops اور ECMP load balance کرتا ہے۔3-tier mein server traffic chaar hops se guzarta hai (access → aggregation → core → aggregation → access). Spine-leaf mein har leaf har spine se jura hai, is liye hamesha do hops aur ECMP load balance karta hai.In 3-tier, server traffic crosses four hops (access → aggregation → core → aggregation → access). In spine-leaf, every leaf connects to every spine, so it is always two hops, with ECMP balancing the load.

❓ vPC کیا ہے اور یہ کونسا مسئلہ حل کرتا ہے؟vPC kya hai aur ye kaunsa masla hal karta hai?What is vPC and what problem does it solve?

vPC دو physical Nexus switches کو ایک logical switch بنا دیتا ہے، تاکہ سرور دونوں سے active-active dual-home ہو سکے — STP blocking اور loop کے بغیر۔vPC do physical Nexus switches ko ek logical switch bana deta hai, taake server dono se active-active dual-home ho sake — STP blocking aur loop ke baghair.vPC makes two physical Nexus switches appear as one logical switch, so a server can dual-home active-active to both with no STP blocking and no loop.

❓ VXLAN کیا ہے اور یہ VLAN سے بہتر scale کیوں کرتا ہے؟VXLAN kya hai aur ye VLAN se behtar scale kyun karta hai?What is VXLAN and why does it scale better than VLAN?

VXLAN Layer 2 کو Layer 3 کے اوپر tunnel کرتا ہے 24-bit VNI (16 ملین segments vs 4094 VLANs) سے۔ اس سے VMs اور workloads fabric میں کہیں بھی move ہو سکتے ہیں۔VXLAN Layer 2 ko Layer 3 ke upar tunnel karta hai 24-bit VNI (16 million segments vs 4094 VLANs) se. Is se VMs aur workloads fabric mein kahin bhi move ho sakte hain.VXLAN tunnels Layer 2 over Layer 3 using 24-bit VNIs (16 million segments vs 4094 VLANs). It lets VMs and workloads move anywhere in the fabric.

❓ ACI contracts سمجھائیں — provided vs consumed۔ACI contracts samjhayein — provided vs consumed.Explain ACI contracts — provided vs consumed.

Contract ACI کی وہ policy ہے جو EPGs کے درمیان ٹریفک کی اجازت دیتی ہے۔ Default deny-all ہے؛ آپ contract کو service EPG پر provided اور user EPG پر consumed کے طور پر لگاتے ہیں۔Contract ACI ki woh policy hai jo EPGs ke darmiyan traffic ki ijazat deti hai. Default deny-all hai; aap contract ko service EPG par provided aur user EPG par consumed ke tor par lagate hain.A contract is the ACI policy that permits traffic between EPGs. Default is deny-all; you attach the contract as provided on the service EPG and consumed on the user EPG.

❓ FC vs FCoE — trade-off کیا ہے؟FC vs FCoE — trade-off kya hai?FC vs FCoE — what is the trade-off?

Fibre Channel ایک مخصوص، lossless storage network ہے۔ FCoE FC frames کو Ethernet پر لے جاتا ہے (convergence)، cabling بچاتا ہے لیکن lossless Ethernet (priority flow control) چاہیے۔Fibre Channel ek makhsoos, lossless storage network hai. FCoE FC frames ko Ethernet par le jata hai (convergence), cabling bachata hai lekin lossless Ethernet (priority flow control) chahiye.Fibre Channel is a dedicated, lossless storage network. FCoE carries FC frames over Ethernet (convergence), saving cabling but requiring lossless Ethernet with priority flow control.

❓ NX-API کیا ہے اور یہ automation میں کیسے مدد کرتا ہے؟NX-API kya hai aur ye automation mein kaise madad karta hai?What is NX-API and how does it help automation?

NX-API Nexus switches پر HTTP/HTTPS API ہے۔ Commands structured JSON/XML میں جواب دیتی ہیں ('| json' سے)، جنہیں scripts اور Ansible text scrape کیے بغیر پڑھ سکتے ہیں۔NX-API Nexus switches par HTTP/HTTPS API hai. Commands structured JSON/XML mein jawab deti hain ('| json' se), jinhein scripts aur Ansible text scrape kiye baghair parh sakte hain.NX-API is the HTTP/HTTPS API on Nexus switches. Commands return structured JSON/XML (with '| json'), which scripts and Ansible can parse reliably instead of scraping text.

❓ VXLAN fabric میں EVPN کیا کرتا ہے؟VXLAN fabric mein EVPN kya karta hai?What does EVPN do in a VXLAN fabric?

EVPN VXLAN کا BGP-based control plane ہے۔ یہ بتاتا ہے کہ کونسا MAC/IP کس VTEP کے پیچھے ہے (l2vpn evpn address-family سے)، اس لیے flood-and-learn کی ضرورت نہیں۔EVPN VXLAN ka BGP-based control plane hai. Ye batata hai ke kaunsa MAC/IP kis VTEP ke peeche hai (l2vpn evpn address-family se), is liye flood-and-learn ki zaroorat nahi.EVPN is the BGP-based control plane for VXLAN. It advertises which MAC/IP addresses live behind which VTEP (using the l2vpn evpn address family), so no flood-and-learn is needed.

❓ خراب VXLAN fabric کو troubleshoot کرنے کا طریقہ بتائیں۔Kharab VXLAN fabric ko troubleshoot karne ka tareeqa batayein.Walk me through troubleshooting a broken VXLAN fabric.

Scope واضح کریں، پھر bottom-up جائیں: interfaces، VLAN/vPC، routing (underlay)، پھر NVE peers اور EVPN۔ اہم commands: show interface brief, show vpc brief, show ip ospf neighbors, show nve peers, show bgp l2vpn evpn summary۔Scope wazeh karein, phir bottom-up jayein: interfaces, VLAN/vPC, routing (underlay), phir NVE peers aur EVPN. Ahem commands: show interface brief, show vpc brief, show ip ospf neighbors, show nve peers, show bgp l2vpn evpn summary.Define the scope, then go bottom-up: interfaces, VLAN/vPC, routing (underlay), then NVE peers and EVPN. Key commands: show interface brief, show vpc brief, show ip ospf neighbors, show nve peers, show bgp l2vpn evpn summary.