A the DHCP
1. What is the DHCP
the DHCP, Dynamic Host Configuration Protocol, formerly known as BOOTP protocol, is a local area network protocol, uses UDP protocols work, commonly used two ports: 67 (DHCP server), 68 (DHCP client). DHCP is commonly used in LAN environments, the main role is to focus on the management, assign an IP address, the client information dynamically obtain an IP address, Gateway address, DNS server address, etc., and can enhance the utilization of addresses. In simple terms, DHCP is an unwanted account password, the protocol automatically assigns IP addresses and other information to the machine within the network.
2.DHCP principle of
DHCP client is generally independent of the host PC LAN. DHCP client DHCP DISCOVER packet sent by the beginning of the DHCP protocol. Continuation of the lease, found that the release behavior of most DHCP IP addresses, etc. are actively initiated by the DHCP client. DHCP ip address Step 4: discover> offer> request> ack (nak). Step refresh DHCP lease: request> ack (nak). Ip DHCP release step of: releasewnr2000v5 1.0.0.8 code is not found rebooting, initreboot state.
Two static routing
1. What is static routing
static routing (English: Static routing), A route way, routing entries (routing entry) by the manual configuration, rather than dynamic decision. Unlike dynamic routing, static routing is fixed and will not change, even if network conditions have changed or re-configuration. Generally, static routes are itemized by the network administrator added to the routing table.
2. Static routing advantages and disadvantages of
advantages: Another benefit of using static routing is that network security is high. Since dynamic routing exchange their routing tables between routers need frequent, and the analysis of the routing table can reveal information about the network topology and network addresses and the like. Therefore, the network for security reasons also can configure static routes. Do not take up network bandwidth, because no static routing update traffic.
Disadvantages: large and complex network environments generally should not use static routing. On the one hand, the network administrator is difficult to fully understand the topology of the entire network; on the other hand, when the network topology and link state changes, the router static routing information in a wide range of needs adjustment, the difficulty of this work and complexity is very high. When a change occurs in the network or network failure, it can not be rerouted, the route is likely to fail.
Three VRRP
1. What is vrrp
VRRP (Virtual Router Redundancy Protocol, referred to as VRRP) is a static gateway routing protocol configuration appears to solve local area network proposed by the IETF single point of failure phenomena, in 1998, has launched a formal protocol standard RFC2338 . VRRP is widely used in the edge of the network, it's designed to support IP data traffic under certain circumstances failover will not cause confusion, allowing the host to use a single router, and promptly in the case of actual first hop router failure is still able to maintain the router connectivity between.
2. Introduction
VRRP is a protocol, it can be the responsibility of a virtual router dynamically allocated to one of the VRRP routers on the LAN. Control VRRP virtual router IP address of the router is called the master router that forwards packets sent to these IP addresses. Once the master fails, this selection process provides a dynamic failover mechanism, which allows a virtual router's IP address as a default host terminal first hop router. LAN access device is a backup protocol. All hosts in a local area network are set to the default gateway, the destination address of such packets is not issued by the host network segment will be sent to the default gateway through three switches, enabling communication of hosts and the external networks. [. 1]
the VRRP is a fault-tolerant routing protocols, routing protocols can also be called backup. All hosts in a local area network are set to the default route, when the destination address of the internal host network segment is not sent, the packet is default route to the external router, enabling communication with an external network host. When the default router is down (ie the port is closed), internal hosts will not be able to communicate with the outside, if the router is set up VRRP, so this time, virtual routing will enable the backup router, in order to achieve full network communication.
In VRRP agreement, there are two important concepts: VRRP virtual router and router, the master router and the backup router. VRRP routers are running VRRP router is a physical entity; refers to the VRRP virtual router is created, is a logical concept. A group of VRRP router to work together to form a virtual router. The virtual logical router external router performance for a unique fixed IP address and MAC address. Role router is a VRRP group have two mutually exclusive: the master router and a backup router, a VRRP group, and only one master role in the router, there may be one or more routers in the backup role VRRP router protocol selected from a group as a master router, ARP is responsible for parsing and forwarding IP packets, the other routers in the group as a backup role and on standby, when for some reason the master router fails, wherein a backup router can be upgraded to a master router delay time instant, since this switch very quickly and do not change the IP address and MAC address, so the system is transparent to the end user.
3. Features
- 1, IP address of the backup, the main function of VRRP. You can provide multiple load-balancing VirtuaI Router election in the network as well as support for multiple logical IP subnets on a single network.
- 2, the optimal path indicates. Routing the VRRP group from the plurality of routers, to ensure that the most readily available Master priority to converge the router.
- 3, minimize unnecessary service interruption. During the primary route to work, does not trigger other low-priority router selects the main route service.
- 4, extensive security. It can use different security policies in a wide variety of interactive environments, it requires minimal configuration and overhead can be strictly verified.
- 5, in the scalable network effectively.
Four OSPF
1. What is ospf
OSPF (Open Shortest Path First Open Shortest Path First) is an interior gateway protocol (Interior Gateway Protocol, referred IGP), for a single autonomous system (autonomous system, AS) in the decision-making routes. Is a link state routing protocol implemented under the Interior Gateway Protocol (the IGP), so that the operation of the internal autonomous systems. The famous Dick Alaska algorithm is used to calculate the shortest path tree. OSPF supports load balancing and routing based on type of service, also supports a variety of routing forms, such as a particular host routing and subnet routes and so on.
2. Define the
OSPF routing protocol is a typical link-state (Link-state) routing protocol, generally used in the same routing domain. Here, the routing domain refers to an autonomous system (Autonomous System), i.e. the AS, which refers to a set of network exchange routing information through a unified policy routing protocol or routing each other. In the AS, all OSPF router maintains a database describing the AS same structure, which is stored in the database information of the corresponding link state routing domain, OSPF router which is calculated by the OSPF routing table database of.
As a link-state routing protocols, OSPF link state multicast data LSA (Link State Advertisement) transmitted to all routers in an area, which is different from the distance vector routing protocol. Routers running distance vector routing protocol is to pass some or all of the routing table to its neighboring routers.
On the exchange of security information, OSPF provides any information exchange between routers, if necessary, can be certified or authentication (Authentication), in order to ensure the dissemination of routing information between the router only trusted. OSPF supports multiple authentication mechanisms, between the various regions and allow different authentication mechanisms. OSPF link state algorithm for use in a broadcast network (e.g., Ethernet) is optimized to take advantage of the hardware capabilities as much as possible to transmit the broadcast link-state packets. Typically link state topology algorithm in a node represents a router. If K routers are connected to the Ethernet link status at the time of the broadcast, on the K router packet will reach a square K. For this purpose, OSPF topology graph allows a node representative of a broadcast network. All router sends link-state packets on each broadcast network, link status report of the network router.
3. Network Type
1.1 point to point network, such as T1 lines, is connected to a single pair of network routers, point to point on the network can always be valid neighbor adjacency relationship, a target on such a network, OSPF packets address used is 224.0.0.5, the multicast address is called AllSPFRouters.
- 2. broadcast network (broadcast), network type proposed by cisco, automatic neighbor discovery elections DR / BDR, hello time 10s.
- 3. Non-broadcast type (NBMA) networks (non-broadcast), proposed by RFC network type, manually configured neighbors, election DR / BDR, hello time 30s.
- 4. multipoint networks (point-to-multipoint), proposed by the RFC, automatic neighbor discovery, no election DR / BDR, hello time 30s.
- The non-multipoint broadcasting, proposed by cisco network type, manually configured neighbors, no election DR / BDR, hello time 30s.
4. advantage - 1, OSPF is true LOOP- FREE (non-loopback route) routing protocol. The advantage derived from the algorithm itself. (And link state shortest path tree algorithm)
- 2, OSPF convergence speed: route change can be transferred to the entire autonomous system in the shortest possible time.
- 3, the concept of region (area) is divided, the autonomous system is divided into different areas, by digest information between routing areas, greatly reducing the amount of routing information needs to be transferred. Also it makes the routing information is not with the expansion of network size and rapid expansion.
- 4, the overhead of the protocol itself to a minimum.
- 5, through strict division level routing (divided into four poles), to provide a more credible routing.
- 6, good security, ospf interface supports plain text and md5 verification.
- 7, OSPF accommodate networks of all sizes, up to thousands.