{"id":2872,"date":"2026-01-17T22:41:00","date_gmt":"2026-01-17T22:41:00","guid":{"rendered":"https:\/\/www.balajibandi.com\/?p=2872"},"modified":"2026-02-06T09:53:00","modified_gmt":"2026-02-06T09:53:00","slug":"86-days-to-ccie-sec-v6-1-lab","status":"publish","type":"post","link":"https:\/\/www.balajibandi.com\/?p=2872","title":{"rendered":"86 Days to CCIE SEC v6.1 Lab"},"content":{"rendered":"\n

Cisco Dynamic ARP Inspection (DAI)<\/mark><\/h2>\n\n\n\n

Layer 2 is often the most vulnerable frontier. Without protection, an attacker can easily execute\u00a0ARP Poisoning<\/strong>\u00a0to redirect traffic, sniff sensitive data, or launch a Man-in-the-Middle (MITM) attack.\u00a0Dynamic ARP Inspection (DAI)<\/strong>\u00a0is the industry-standard solution for locking down these gaps.<\/p>\n\n\n\n

1. The Concept: Why DAI Matters<\/mark><\/h2>\n\n\n\n

ARP is inherently trusting; it accepts any reply even if no request was sent. DAI ends this “blind trust” by intercepting all ARP packets on untrusted interfaces<\/strong> and validating them against a source of truth\u2014typically the DHCP Snooping Binding Database<\/strong>.<\/p>\n\n\n\n

    \n
  • Trusted Interfaces:<\/strong>\u00a0Typically connected to switches, routers, or servers. Traffic bypasses DAI checks.<\/li>\n\n\n\n
  • Untrusted Interfaces:<\/strong>\u00a0Ports where end-users connect. Every ARP packet is inspected.<\/li>\n\n\n\n
  • The Validation Logic:<\/strong>\u00a0If the Sender MAC and Sender IP in the ARP packet do not match an entry in the binding table, the switch drops the packet and logs the violation.<\/li>\n<\/ul>\n\n\n\n
    \n\n\n\n

    2. Real-World Use Case: The Office “Sniffer”<\/mark><\/h2>\n\n\n\n

    Imagine an employee plugs a laptop into a wall jack and runs an ARP spoofing tool. They claim to be the Default Gateway (10.1.1.1<\/code>).<\/p>\n\n\n\n

      \n
    • Without DAI:<\/strong>\u00a0Other workstations update their ARP tables with the attacker’s MAC. Traffic meant for the internet now flows through the attacker’s laptop.<\/li>\n\n\n\n
    • With DAI:<\/strong>\u00a0The switch sees an ARP reply from an untrusted port claiming to be\u00a010.1.1.1<\/code>. It checks its DHCP Snooping table, sees that the port is actually assigned to\u00a010.1.1.55<\/code>, and\u00a0immediately drops the malicious packet<\/strong>.<\/li>\n<\/ul>\n\n\n\n
      \n\n\n\n

      3. Lab Build: Sample Configuration<\/h2>\n\n\n\n

      DAI\u00a0requires<\/strong>\u00a0DHCP Snooping\u00a0to be enabled first, as it provides the database DAI uses for validation.<\/p>\n\n\n\n

      Step 1: Enable DHCP Snooping (Prerequisite)<\/p>\n\n\n\n

      SW1(config)# ip dhcp snooping<\/em>\nSW1(config)# ip dhcp snooping vlan 10<\/em>\nSW1(config)# interface GigabitEthernet1\/0\/24  # Uplink to DHCP Server\/Router<\/em>\nSW1(config-if)# ip dhcp snooping trust<\/em>\n\n\nDiagram (Source from the Internet)<\/mark><\/strong><\/code><\/pre>\n\n\n
      \n
      \"\"<\/figure>\n<\/div>\n\n\n
      <\/p>\n\n\n
      \n
      \"\"<\/figure>\n<\/div>\n\n\n
      Happy Labinggggggggggggggggg !<\/strong><\/p>\n\n\n\n
      <\/p>\n","protected":false},"excerpt":{"rendered":"
      Cisco Dynamic ARP Inspection (DAI) Layer 2 is often the most vulnerable frontier. Without protection, an attacker can easily execute\u00a0ARP Poisoning\u00a0to redirect traffic, sniff sensitive data, or launch a Man-in-the-Middle (MITM) attack.\u00a0Dynamic ARP Inspection (DAI)\u00a0is the industry-standard solution for locking down these gaps. 1. The Concept: Why DAI Matters ARP is inherently trusting; it accepts […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[11,2],"tags":[],"class_list":["post-2872","post","type-post","status-publish","format-standard","hentry","category-ccie-sec","category-cisco"],"_links":{"self":[{"href":"https:\/\/www.balajibandi.com\/index.php?rest_route=\/wp\/v2\/posts\/2872","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.balajibandi.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.balajibandi.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.balajibandi.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.balajibandi.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=2872"}],"version-history":[{"count":2,"href":"https:\/\/www.balajibandi.com\/index.php?rest_route=\/wp\/v2\/posts\/2872\/revisions"}],"predecessor-version":[{"id":2877,"href":"https:\/\/www.balajibandi.com\/index.php?rest_route=\/wp\/v2\/posts\/2872\/revisions\/2877"}],"wp:attachment":[{"href":"https:\/\/www.balajibandi.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=2872"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.balajibandi.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=2872"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.balajibandi.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=2872"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}