High-end technology: The secret of switch frame failure

High-end technology: The secret of the switch frame failure, the solution to the fault caused by the switch frame failure, to introduce the solution to the switch frame failure, there may be many people who don't know how to optimize the switch frame failure. It doesn't matter. After reading this article, you will certainly have a lot of GAINS. I hope this article will teach you more things.

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.