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.
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 220.127.116.11
- 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.