Hello.
I will share with you how to deal with the problem that server can not access S6700 management IP address.
1. Problem Description
Customer report that: From Host A (10.70.1.2) in E9000 server can’t access SW-A (10.70.1.24) anytime and can’t access SW-B (10.70.1.25) when CX911’s eth-trunk 10 is Down.
2 Problem Analysis
First, the network works with RSTP protocol, normally, there are some interface will be blocked by STP.
1. When interface Eth-trunk 10 (connected between SW-A and CX911) is UP, After checked all interface STP status, the interface Eth-trunk 20 is blocked,the traffic path is as following:
For SW-A (10.70.1.24), When ping SW-A(10.70.1.24) from Host A (10.70.1.2) , The traffic packets reach SW-A from interface eth-trunk 10, it is L2 interface. This packets can not be sent to Meth0/0/1, Because it is L3 interface. And there is not MAC address forwarding table for the MAC address of SW-A(SW self), These packets will be broadcast to Gateway device S3218TP through interface XG0/0/1, and then the packets will be forwarded to Meth0/0/1 of SW-A. And then SW-A response the ICMP response packets to Gateway device S3218T, and then send back to SW-A through interface XG0/0/1, At this time, the packets will be dropped because SW-A find the source MAC address of these packets are itself, this is illegal, so SW-A dropped these packets.
And for SW-B (10.70.1.25), when ping it from Host A(10.70.1.2), According to above traffic path, the path is signal direction and L2 forwarding, there is not situation like ping SW-A. So it can be reached normally, So at this traffic path, Host A can ping SW-B interface Meth0/0/1(10.70.1.25) normally.
2. When interface Eth-trunk 10 (connected between SW-A and CX911) is Down, After checked all interface STP status, the traffic path is as following:
According to above path, it root cause is same with the before traffic path. as below:
For SW-A (10.70.1.24), When ping SW-A(10.70.1.24) from Host A (10.70.1.2) , The traffic packets reach SW-A from interface eth-trunk 0, it is L2 interface. This packets can not be sent to Meth0/0/1 directly, Because it is L3 interface. And there is not MAC address forwarding table for the MAC address of SW-A(SW self), These packets will be broadcast to Gateway device S3218TP through interface XG0/0/1, and then the packets will be forwarded to Meth0/0/1 of SW-A. And then SW-A response the icmp response packets to Gateway device S3218T, and then send back to SW-A through interface XG0/0/1, At this time, the packets will be dropped because SW-A find the source MAC address of these packets are itself, this is illegal, so SW-A dropped these packets. So it can not be reached.
And for SW-B (10.70.1.25), when ping it from Host A(10.70.1.2), According to above traffic path, The traffic packets reach SW-B from interface eth-trunk 20, it is L2 interface. This packets can not be sent to Meth0/0/1 directly, because it is L3 interface. And there is not MAC address forwarding table for the MAC address of SW-B(SW self), These packets will be broadcast to SW-A through interface eth-trunk 0, and then the packets will be broadcast to Gateway device S3218T, and then the packets will be forwarded to Meth0/0/1 of SW-B. When SW-B received request packet, SW-B will response the icmp response packets to Gateway device S3218T, and then send back to SW-B through interface XG0/0/1, and then sent back to SW-B through interface Eth-trunk 0, At this time, the packets will be dropped because SW-B find the source MAC address of these packets are itself, this is illegal, so SW-B dropped these packets. So it can not be reached.
3 Root Cause
The STP protocol and the network topology make the traffic will be sent to SWs 2 times, this situation make the packets sent by SW was sent back to SW, these packets will be dropped as the source MAC address is SW, this is illegal.
4 Solutions
To configure VLANif 4032 as the management interface, and then move the IP address of Meth0/0/1 to Vlanif 4032, as following. This solution has been configured on SW-A and SW-B when remote session.
SW-A:
interface Vlanif4032
ip address 10.70.1.24 255.255.255.128
SW-B:
interface Vlanif4032
ip address 10.70.1.25 255.255.255.128
Other Solution:
If customer want to use Meth0/0/1 interface to manage SWs, he have to make sure Host servers and SW devices in different subnet, make sure the route is reachable, and then they can access SWs through L3 network only.From group: WLAN
This is my solution, how about yours? Go ahead and share it with us!
