Different MTUs are displayed in the display isis interface command output on an S series switch


Q: In the display isis interface command output, why is the MTU on a broadcast network 1497 bytes whereas the MTU on a P2P network 1500 bytes?
A: By default, the physical MTU of Ethernet interfaces are 1500 bytes.
On a P2P network that has PPP enabled, the MTU is 1500 bytes in the display isis interface command output.
On a broadcast network, a 3-byte Local Link Control (LLC) field is added to the data field according to the 802.3 link protocol encapsulation format, and the value of the LLC field is FEFE03. Therefore, in IS-IS, the actual length of the data to be transmitted is 1497 bytes, which is 3 bytes shorter than the physical MTU.

Other related questions:
Why cannot fan information be displayed in the display device command output and why is the ALM indicator of AC power yellow when the S7700&S9700's fan is operating
The monitoring unit (MCU or CMU) fails to communicate with the fan or AC power supply. NOTE: If you need to buy the CMU, contact Huawei local office.

The display interface brief and display interface commands display different interface bandwidth usage. Why
The display interface brief and display interface commands should display the same interface bandwidth usage. By default, the interval for traffic statistics on an interface is 300s. Within the first 300s, the statistics are instable. Wait for 300s and check the statistics, or run the set flow-stat interval command to change the interval for traffic statistics.

What are the meanings of flags in the display fib command output for S series switches
Q: What are the meanings of flags in the display fib command output? A: The values of flags are as follows: B: indicates a blackhole route, that is, a route with the outbound interface being NULL0. D: indicates a route generated by a dynamic routing protocol such as IS-IS, OSPF, BGP, or RIP. G: indicates a gateway route, that is, a route destined for a gateway. H: indicates a host route. L: indicates a route generated by Address Resolution Protocol (ARP) or End System to Intermediate System (ESIS) routing exchange protocol, which is common in VLAN-ARP scenarios. S: indicates a static route, that is, a route configured using the ip route-static command or configured on the NMS. U: indicates that a route is reachable.

What is the meaning of MTU in the display mpls interface verbose command output
After you run the display mpls interface verbose command, the following information is displayed: display mpls interface vlanif 100 verbose No : 1 Interface : Vlanif100 Status : Up TE Attribute : Disable Static LSPCount : 0 Static CR-LSPCount : 0 LDP LSPCount : 0 RSVP LSPCount : 0 MPLS MTU : - Interface MTU : 1500 Effective MTU : 1500 TE FRR : Disable Interface Index : 0xd1MTUs in the preceding command output indicate different meanings: MPLS MTU: MTU configured using the mpls mtu command. Interface MTU: MTU negotiated on the interface. Effective MTU: Smaller MTU between MPLS MTU and Interface MTU. When the MPLS MTU or Interface MTU changes, the configuration takes effect only after you restart the interface.

What should I do when a CE series switch license file changes to the trial state
If a license in trial state expires, successfully delivered configurations of a licensed feature will be retained and take effect. You are allowed to delete existing service configurations related to the licensed feature, but not to add new configurations. Therefore, apply for a new license and activate it before the current license expires. Otherwise, services will be affected.

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