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Updated Lessons

Want to know what’s new? Here you will an overview of recently updated lessons.

  • IPv6 Router Advertisement with Router Lifetime 0 Packet Capture October 2026 Wireshark capture of two IPv6 Router Advertisements from a Cisco router: a normal RA with router lifetime 1800, then a final RA with router lifetime 0 and prefix lifetimes 0 when the router stops advertising. Download the pcap.
  • OSPFv3 Authentication Trailer Packet Capture October 2026 Wireshark capture of an OSPFv3 Hello with the Authentication Trailer (RFC 7166): AT bit, HMAC-SHA-1 authentication data, Security Association ID and the 64-bit cryptographic sequence number. No IPsec needed. Download the pcap.
  • BFD Control Packet Capture October 2026 Wireshark capture of a BFD control packet between two Cisco routers: UDP 3784, TTL 255, session state Up, discriminators, detect multiplier and the TX, RX and echo intervals. Download the pcap.
  • DNS Query and Response Packet Capture October 2026 Wireshark capture of a DNS A record lookup for cisco.com: UDP 53, transaction ID, flags (RD, RA), the answer with its TTL, authority and additional records, and DNS name compression. Download the pcap.
  • VRRP Advertisement Packet Capture October 2026 Wireshark capture of VRRPv2 advertisements and gratuitous ARP from Cisco routers: 224.0.0.18, IP protocol 112, TTL 255, virtual router ID, priority, virtual MAC 00:00:5e:00:01:01 and preemption. Download the pcap.
  • BGP Role Capability and OTC Attribute Packet Capture October 2026 Wireshark capture of BGP Roles (RFC 9234) between a provider and a customer: the BGP Role capability in the OPEN message, a connection collision, and the Only to Customer (OTC) attribute in UPDATE messages. Download the pcap.
  • DHCPv6 Solicit, Advertise, Request, Reply Packet Capture October 2026 Wireshark capture of a stateful DHCPv6 exchange (SARR): Solicit, Advertise, Request and Reply with DUID, IA_NA, T1/T2, lifetimes, DNS server and domain search list. Download the pcap.
  • EIGRP Query and Reply Packet Capture October 2026 Wireshark capture of an EIGRP Query, Reply and the ACKs in between: multicast query, unicast reply, sequence and acknowledge numbers, and infinite delay for a lost route. Download the pcap.
  • MPLS L3VPN Label Stack Packet Capture October 2026 Wireshark capture of ICMP traffic through an MPLS Layer 3 VPN: the transport label and VPN label in the request, a single VPN label in the reply after penultimate hop popping. Download the pcap.
  • MPLS LDP Hello Packet Capture October 2026 Wireshark capture of a single MPLS LDP Hello message from a Cisco IOS router: UDP 646, 224.0.0.2, hold time, LSR ID and the IPv4 transport address. Download the pcap.
  • MPLS LDP Session and Label Mapping Packet Capture October 2026 Wireshark capture of an MPLS LDP session between two Cisco routers: hellos, the TCP 646 session, Initialization, KeepAlive, Address and Label Mapping messages with implicit null. Download the pcap.
  • BGP Role Mismatch Packet Capture October 2026 Wireshark capture of a BGP Role mismatch (RFC 9234): two FRRouting routers both configured as provider, the BGP Role capability in the OPEN messages and the OPEN Message Error / Role Mismatch NOTIFICATION. Download the pcap.
  • VTP Client Overwrites VTP Server October 2026
  • Ping on the Linux Loopback Interface Packet Capture October 2026 Wireshark capture of a ping to 127.0.0.1 on the Linux loopback interface (lo): all-zero MAC addresses, 127.0.0.1 as source and destination, a 13 microsecond round trip and the timestamp Linux ping puts in the ICMP data. Download the pcap.
  • EIGRP Static Neighbor Unicast Hello Packet Capture October 2026 Wireshark capture of EIGRP with static neighbors: unicast Hellos instead of 224.0.0.10, K-values and hold time, the Init flag exchange, End of Table updates with classic metric TLVs and the ACKs. Download the pcap.
  • BGP UPDATE with Multiple Prefixes Packet Capture October 2026 Wireshark capture of a BGP UPDATE that carries eight prefixes with one set of path attributes, compared with eight separate UPDATEs when every prefix has a different MED. Shows how BGP packs NLRI. Download the pcap.
  • gRPC on Cisco IOS XR Packet Capture October 2026 Wireshark capture of a Python gRPC client configuring a Cisco IOS XR router without TLS: HTTP/2 preface, ReplaceConfig and GetConfig RPCs, plaintext credentials in the headers, YANG JSON in protobuf and grpc-status trailers. Download the pcap.
  • BGP Update-Source on One Side Packet Capture October 2026 Wireshark capture of an iBGP session between loopbacks where only one router has update-source configured: a TCP RST for the wrong source address, then a working session opened from the other side. Download the pcap.
  • L2TPv3 Control Connection and Session Setup Packet Capture October 2026 Wireshark capture of an L2TPv3 pseudowire coming up between two Cisco routers: IP protocol 115, a tie-breaker collision, SCCRQ/SCCRP/SCCCN, ICRQ/ICRP/ICCN, control connection and session IDs. Download the pcap.
  • VTP Version 2 Summary and Subset Advertisement Packet Capture October 2026 Wireshark capture of a VTP version 2 summary advertisement and subset advertisement from a Cisco switch: domain name, configuration revision, followers, MD5 digest and the VLAN list. Download the pcap.