Lesson 9 - Implement Secure Network Designs Flashcards
(103 cards)
Typical weaknesses in secure network design include:
Single points of failure
Complex dependencies
Availability over confidentiality and integrity
Lack of documentation and change control
Overdependence on perimeter security
In Ethernet, a networking device that receives incoming data, reviews the destination MAC address against an internal address table, and sends the data out through the port that contains the destination MAC address.
Switches
Switches work at layer 2 of the OSI model and make forwarding decisions based on the hardware or Media Access Control (MAC) address of attached nodes.
provide a bridge between a cabled network and wireless clients, or stations.
Wireless access points
Access points work at layer 2 of the OSI model.
A network device that links dissimilar networks and can support multiple alternate paths between location-based parameters such as speed, traffic loads, and price.
Routers
forward packets around an internetwork, making forwarding decisions based on IP addresses.
Routers work at layer 3 of the OSI model.
Routers can apply logical IP subnet addresses to segments within a network.
Apply an access control list (ACL) to filter traffic passing in or out of a network segment.
Firewalls
Firewalls can work at layer 3 of the OSI model or higher.
Distribute traffic between network segments or servers to optimize performance.
Load balancers
Load balancers can work at layer 4 of the OSI model or higher.
Host name records and perform name resolution to allow applications and users to address hosts and services using fully qualified domain names (FQDNs) rather than IP addresses.
Domain Name System (DNS) servers
DNS works at layer 7 of the OSI model. Name resolution is a critical service in network design.
Abuse of name resolution is a common attack vector.
Occurs between nodes on the same local network segment that are all in the same broadcast domain. A broadcast domain is either all the nodes connected to the same physical unmanaged switch, or all the nodes within a virtual LAN (VLAN) configured on one or more managed switches.
Layer 2 forwarding
At layer 2, each node is identified by the network interface’s hardware or Media Access Control (MAC) address. A MAC address is a 48-bit value written in hexadecimal notation, such as 00-15-5D-F4-83-48.
Occurs between both logically and physically defined networks. A single network divided into multiple logical broadcast domains is said to be subnetted.
Layer 3 forwarding, or routing
Multiple networks joined by routers form an internetwork. At layer 3, nodes are identified by an Internet Protocol (IP) address.
Maps a network interface’s hardware (MAC) address to an IP address.
Address Resolution Protocol (ARP)
Normally a device that needs to send a packet to an IP address but does not know the receiving device’s MAC address broadcasts an ARP Request packet, and the device with the matching IP responds with an ARP Reply.
IP provides the addressing mechanism for logical networks and subnets.
Internet Protocol (IP)
A 32-bit IPv4 address is written in dotted decimal notation, with either a network prefix or subnet mask to divide the address into network ID and host ID portions. For example, in the IP address 172.16.1.101/16, the /16 prefix indicates that the first half of the address (172.16.0.0) is the network ID, while the remainder uniquely identifies a host on that network. This /16 prefix can also be written as a subnet mask in the form 255.255.0.0.
Logically separate network, created by using switching technology. Even though hosts on two VLANs may be physically connected to the same cabling, local traffic is isolated to each VLAN so they must use a router to communicate.
virtual LANs (VLANs).
Allows a router to perform dynamic updates to its routing table based on route data exchanged with other routers.
routing protocols
A path vector routing protocol used by ISPs to establish routing between one another.
Border Gateway Protocol (BGP)
A link-state routing protocol used on IP networks
Open Shortest Path First (OSPF)
IGRP is a distance vector-based routing protocol using a metric composed of several administrator weighted elements including reliability, bandwidth, delay, and load. E(nhanced)IGRP, the version now in use, supports classless addressing and more efficient route selection.
Enhanced Interior Gateway Routing Protocol (EIGRP)
A distance vector-based routing protocol that uses a hop count to determine the distance to the destination network.
Routing Information Protocol (RIP)
A portion of a network where all attached hosts can communicate freely with one another.
segment
Assuming an Ethernet network, network segments can be established physically by connecting all the hosts in one segment to one switch and all the hosts in another segment to another switch. The two switches can be connected by a router and the router can enforce network policies or access control lists (ACL) to restrict communications between the two segments.
A situation where hosts on one network segment are prevented from or restricted in communicating with hosts on other segments.
Segregation
Assuming an Ethernet network, network segments can be established physically by connecting all the hosts in one segment to one switch and all the hosts in another segment to another switch. The two switches can be connected by a router and the router can enforce network policies or access control lists (ACL) to restrict communications between the two segments.
Because enterprise networks typically feature hundreds of switching appliances and network ports (not to mention wireless access and remote access), segmentation is more likely to be enforced using virtual LANs (VLANs). Any given switch port can be assigned to any VLAN in the same topology, regardless of the physical location of the switch. The segmentation enforced by VLANs at layer 2 can be mapped to logical divisions enforced by IP subnets at layer 3.
In networking infrastructure, an area of a network where the security configuration is the same for all hosts within it. In physical security, an area separated by barriers that control entry and exit points.
Zone
A private network that is only accessible by the organization’s own personnel.
Intranet (private network)
A segment isolated from the rest of a private network by one or more firewalls that accepts connections from the Internet over designated ports.
demilitarized zones (DMZs)
This is a zone permitting anonymous access (or perhaps a mix of anonymous and authenticated access) by untrusted hosts over the Internet.
Internet/guest
A private network that provides some access to outside parties, particularly vendors, partners, and select customers.
extranet