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
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.


RIPv2

  • Supports VLSM (subnet mask carried in updates)
  • Supports authentication
  • Updates sent to multicast address 224.0.0.9
  • Poison Reverse updates explicitly indicate that a network is unreachable
  • Up to 25 networks per RIP update

EIGRP

  • 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

  • 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

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.

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Author: Mo Moghaddas

Traveler. Casual investor. Hobbyist landscape photographer loving Networks. Blockchain/Cryptocurrency enthusiast. Internet citizen!

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