CCIE Security written: 1 – General Networking

Highlights of CCIE Security written Study Guide

Cisco switches have VLAN 1 already configured which cannot be removed for management purposes, because protocols such as CDP and spanning tree will be active.

Telnet (TCP) Packet Flow

Step 3: The PC sends a segment that acknowledges (ACK) the router’s reply. The first three steps are commonly known as the  TCP three-way handshake . It is possible for four packets to start a session if a parameter needs to be negotiated. 

A gratuitous ARP is an ARP request with its own IP address as the target address. It refreshes a device’s ARP table entries and also looks up duplicate IP addresses. Routers are devices that can send a gratuitous ARP.


  • Supports VLSM (subnet mask carried in updates)
  • Supports authentication
  • Updates sent to multicast address
  • Poison Reverse updates explicitly indicate that a network is unreachable
  • Up to 25 networks per RIP update


  • Smooth Route Trip Time (SRTT): Time taken to send a packet reliably to an acknowledgment. SRTT is the average delta between the time a packet is sent and the arrival of the neighbor’s acknowledgment.
  • Retransmission Timeout (RTO): RTO is the time a router waits for the arrival of the neighbor’s acknowledgment.


  • OSPF is faster because it sends the link update and then calculates the local routing table. RIP calculates the local routing table and then sends an update.
  • By default, loopback interfaces are stub hosts in OSPF and are advertised as 32-bit hosts.


BGP peers initially exchange full BGP routing tables.

  • An ISDN BRI consists of two 64-kbps services (B channels) and one 16-kbps signaling channel (D channel).
  • An ISDN PRI consists of 23 B or 30 B channels, depending on the country.
  • The B channel sends data and the D channel primarily controls signaling.

HDLC is a connectionless protocol that relies on upper layers to recover any frames that have encountered errors across a WAN link.

  • PPP (connection-oriented), resubmits packets damaged in transmission over the WAN.
  • PPP has the added function of allowing authentication to take place before any end user data is sent across the link.
  • Link establishment—Link Control Protocol (LCP) packets are sent to configure and test the link.
  • Network layers—In this phase, Network Control Protocol (NCP) packets determine which protocols are used across the PPP link.
  • IP Control Program (IPCP) allows IP connectivity

The four AS5300s in Figure 2-20 can also share the load of incoming calls using Stack Group Bidding Protocol (SGBP), which is used when multiple PPP, or multilink PPP (MPPP), sessions are in use.

Share this!

Author: Mo Moghaddas

Building to give users more time back and make scheduling a pleasant experience.

Leave a Reply

Your email address will not be published.

This site uses Akismet to reduce spam. Learn how your comment data is processed.