What is the hidden danger of switch frame sealing failure?

For a long time before the frame Sealing Failure of a switch occurs, our network is normal. You can force the super engine to set the Trunk of IEEE 802.1Q. After the network is stable, connect the jumper to the igabitEthernet 3/48 interface.

Switch frame Sealing Failure

A strange problem occurs in the VLAN of the two Departments in the office area of the organization. Some websites on the Internet can access normally, but some websites cannot access it. emails received through Outlook or Foxmail are normal, it is also normal to send small emails without attachments, but it cannot be normally sent when sending large emails or emails containing attachments. Internet access is normal in other office areas of the Organization. The topology of the network.

Analysis of switch frame Sealing Failure

The Office Area of the user's PC is about 2 to 5 minutes away from the core switch ~ 3 km, the office area has two departments, which belong to different VLANs. Therefore, we have placed the annett Network Management Switch AT-8024 in the office area, connecting to our core switch Cisco 6509 via optical fiber and optical transceiver in the middle Cisco 6509 is configured as: super engine SUP720, a 16-port Gigabit Optical module WS-X6816-GBIC, A 48-port fast switching electrical module WS-X6548-RJ-45 ).

Trunk is set up on the corresponding port connecting the optical transceiver's 6509 and the annett switch's frame sealing failure. The annett switch is divided into two VLANs, 172.25.6.0/24 or earlier, VLAN6) and 172.25.7.0/24 (VLAN7), machines in the two Departments are connected to their respective VLANs. Other office areas of the Convergence layer switch Cisco 3550) directly through the optical module connected to the 6509 WS-X6816-GBIC optical module.

The entire network uses an IBM X235 server as the NAT and DHCP servers. The data of all VLANs is first converted to the NAT address before accessing the Internet through the edge router. When we encountered the above strange problem, we initially suspected that there was a problem with the NAT and 6509 settings. However, after checking, the VLAN6 and VLAN7 configurations are exactly the same as those in other office areas. Because the Internet access of other VLANs except the two VLANs is completely normal, the following steps are taken.

◆ Delete All VLAN information of VLAN6 and VLAN7 from the frame failure of the annett Network Management Switch, and place all ports in VLAN1, which is completely the same as vlan1. However, the problem persists, while users in VLAN1 in other office areas still access the Internet normally.

◆ From step 1) we infer that the problem is not based on VLAN division. We suspect that the optical transceiver or annett switch has a frame failure, as a result, the normal optical transceiver or annett switch used in other office areas is replaced, and the problem persists.

◆ Is it a problem of link quality? Hurry up and find two PCs, one connected to annett switch, unplug the optical transceiver from the 6509 network cable, directly connect to another machine, configure the IP address of the same network segment, the maximum packet sent is B ping, but the result is disappointing. The delay is only a few milliseconds, which indicates that the link is correct.

◆ When we were "poor at technology", we connected the optical transceiver and the 6509 again. We still pinged the gateway of the VLAN 172.25.6.210 on the 6509 through the PC Connected to annett, the problem occurs. When ping with a small packet, there is basically no latency, but when ping with a large packet is close to 18024b, Cisco supports the maximum packet.) packet loss occurs during ping. The problem must be solved here.

◆ Re-check the configurations of annett, 6509, and NAT servers. We found the following problem: Configure VLAN6 and VLAN7 on annett, and add the corresponding ports to VLAN: add vlan 6 ports = 23 frame = untagged.

LAN switches work on the second layer of OSI and can be understood as a multi-port bridge. Therefore, they are traditionally called Layer 2 switches. At present, the exchange technology has extended some of the functions of the third layer of OSI, the layer-3 exchange does not spread broadcast packets, but directly uses the dynamically established MAC address to communicate. It seems that the layer-3 information can be understood.

Such as IP addresses and ARP, which provide routing functions based on IP addresses, IPX, and other protocols between multicast and virtual networks. The smooth implementation of these functions is due to the addition of specialized Integrated Circuits (ASIC, change the traditional instruction from software processing to the embedded instruction of ASIC chip.

This accelerates packet forwarding and filtering, ensuring high-speed linear routing and service quality. Currently, if you do not need a wide area network, you will no longer use vrouters that are expensive and have limited bandwidth in the network creation solution.

The development of exchange technology allows geographically dispersed organizations to logically become a new working group, and members of the same working group can change their physical addresses without reconfiguration of nodes, this is the so-called VLAN technology ).

Using a LAN switch to build a virtual network is to divide the logic of the original large broadcast area (all ports of the switch) into several "subbroadcast areas ", the broadcast packets in the subbroadcast area are only transmitted in the broadcast area, but cannot be received in other broadcast areas.

VLAN uses the exchange technology to effectively separate the traffic, so as to better utilize the bandwidth, and logically split the actual LAN infrastructure into multiple subnets, it allows various local networks to run different application protocols and topologies. For more information, see the rules.

1. Correct Interpretation and test of vswitch Port
2. Summarize the market status of high-end Switches
3. Focuses on core layer switch faults
4. PythonAndroid
5. Let's talk about the stacking of Ethernet switches.