dhcp snooping

I. Working principle: A. After the specified VLAN is enabled for DHCP snooping, the ports are divided into trusted interfaces and untrusted interfaces, the default VLAN all interfaces become untrusted interfaces, and the trusted interfaces need to be set manually. B. For the untrusted interface, you can only receive DHCP request messages and do not send

The method used is to assign IP to the user by DHCP, and then limit the way that these users can only use dynamic IP, if it is changed to static IP mode can not connect to the network; that is, the DHCP snooping function is used. Example: Version 12.1No service padService Timestamps Debug UptimeService Timestamps Log uptimeNo service password-encryptionService

In the previous two sections, we analyzed the IGMP snooping process based on the IGMP snooping code implemented in linux2.6.32. This section analyzes the functionality required to implement IGMP snooping based on the first two sections One, data structure For the implementation of a sub-layer function, the most important is the establishment of data structures.

addressesDHCP Snooping: a DHCP listener that records the user information applied for an IP address from a layer-2 device.The DHCP packet format is shown in the right figure. The fields are defined as follows: packet format Fields in the message are described as follows: op, the packet type. 1 indicates the request message, and 2 indicates the Response Message.

address conflicts Clients do not have to use the DHCP service to get IP, or you can set the IP address in a statically specified manner. This will greatly increase the likelihood of network IP address conflicts. Introduction to DHCP snooping technology The DHCP spanning is a control plane feature. The ability to cl

-config Building configuration ... Current configuration:1464 bytes Version rg0s 10.1.00 (1), Release (11758) (Fri Mar 12:53:11 CST 2007-NPRD Hostname Ruijie VLAN 1 IP helper-address 192.18.100.1 IP helper-address 192.18.100.2 IP DHCP relay information option DOT1X Interface Gigabitethernet 0/1 Interface Gigabitethernet 0/2 Interface Gigabitethernet 0/3 No Switchport IP helper-address 192.168.200.1 IP helper-address 192.168.200.2 Interface VLAN 1 IP a

Application examples My school is a student apartment, PC owns about 1000 units. Using DHCP assigned IP address, with 4 C class addresses, the actual number of addresses available is about 1000. Because of the frequent presence of private DHCP servers in the building, a large number of hosts cannot be assigned to legitimate IP addresses, and because a significant number of hosts specify IP addresses, confl

, generally, this address is the same as the MAC address of the client. If an attacker modifies the CHADDR In the DHCP packet without modifying the MAC address of the client, and implements Dos attacks, Port Security does not work, DHCP sniffing technology can check the CHADDR field in the DHCP request message to determine whether the field matches the

Original link http://louisnetwork.blog.sohu.com/111972027.html Some tests involve IGMP snooping at work. When it comes to IGMP snooping, it is inevitable that IGMP proxy will come to mind. Sometimes, you may think more and think more about it.What is the difference between them? First, let's look at the figure below. L2 Switch enables IGMP snooping, and router1

PIM SM + IGMP snooping suitability test test topology Figure 1 BootstrapThe BOOTSTRAP protocol is used to designate and announce the RP, the BOOTSTRAP protocol ensures that the entire network chooses a unique BSR (boot router) through Bootstrap messages, BSR collects the RP information in the network and floods all PIM routers in the PIM domain; C-RP learned about BSR, By sending candidate-rp-advertisement messages to BSR via unicast, BSR

plan: Using bound variables to snoop If you do not use a binding variable for snooping, the default selectable rate (for example, 5%) is used for predicate conditions where the selectable rate may vary depending on the specific input value. Binding variable snooping (bind peeking) is introduced in Oracle 9i, whether binding variables are enabled to spy on the control of _optim_peek_user_b

PIM SM + IGMP snooping suitability Test (ii) Introduction to TTL issuesThe two questions and answers in the previous section are based on theoretical analysis and experimental validation, and this section describes the problems encountered in experiments and experiments.Test topology Figure 1 Experiment DescriptionBefore doing experiments to verify the technical problems, first of all to clarify the purpose of the experiment, then detailed

Original link http://blog.163.com/song_jk/blog/static/235693562007022112149449/ At present, in an IP network, the carrier's network does not want to provide users in the form of xDSL for the purpose of providing more services, but directly provides a uniform width interface, this form is particularly common in some broadband communities. Currently, in addition to Internet services, most applications in broadband communities are provided with IPTV. In the promotion of IPTV, it is generally requi

1. pseudo dhcp server. The working principle of Dhcp is probably that the client first broadcasts the dhcp discovery message. The dhcp server in this section returns the dhcp offer message, and the client sends the dhcp request me

can quickly find its associated multicast group database entries U32 queries_sent;//the number of times a query package has been sent }; Where the port list is used to add all the corresponding bridges to the addr of the multicast group Next points to the next multicast port, and the next multicast group address is addr, only the port value is different. Where mglist is used to add the multicast port to the Mglist linked list of port, through the mglist linked list of the bridge port, can find