问题

在使用NE40e后，SSH Session中通过“上”、”下”回滚长命令总会遇到显示问题，必须多按几个回车才能刷掉显示乱的屏幕，如下所示：

此问题困扰我很长时间了，一直没仔细研究过，这次趁着有些时间想彻底把这个问题解决下。下面是整个ssh的过程：

SCRT ----- 1st 跳板机 ----- 2nd 跳板机 ----- NE40E

解决

通过对比发现只有当通过脚本登录NE40E时才会有此问题，如果直接SSH登录NE40E就不会有问题，那么问题跟脚本相关么？

Background

实验环境打算用trex打流，然后用下面环境测试cable，但物理server配置好路由后，发现只能收路由，不转发流量，我们确认已经开启了ipv4转发的指令，路由也是正常的，但就是不work，所以我在EVE NG的环境上搭了一个类似的环境，确认下是否是trex本身的问题；

# sysctl -a |grep net.ipv4.conf.all.forwarding
net.ipv4.conf.all.forwarding = 1

对于trex内容，请看我之前的相关文章：http://www.zhaocs.info/tag/trex；

背景

Telnet是常用的远程设备远程登录协议，通过如SecureCRT，Item2等终端软件，可以很容易的登录各种支持Telnet协议的设备，但有时候根据不同的终端设备，会需要一些特殊的设置，这就涉及Telnet协商，此篇文章就是整理下Telnet的几种模式及之间的区别，也包含如何更改这些模式的操作方法；

问题

我们可以通过一个问题来展开讨论，如下环境：

PC---(SSH)---CentOS---(Telnet)---KVM(vNE40E)

我们发现登录vNE40E后无法退格，连续回车会有断行，如下所示：

[root@beihe-terminal-server ~]# CR1
Trying 172.16.211.165...
Connected to 172.16.211.165.
Escape character is '^]'.


<HUAWEI>
<HUAWEI>

<HUAWEI>
<HUAWEI>dis ver^H^H^H^H  <<< 4个退格键

通过“Crtl + ]”退出当前session，然后通过“status”来查看当前Telnet连接的模式，可以看到是 “obsolete linemode”， 过时的Line mode？😂：

<HUAWEI>^]
telnet> status
Connected to 172.16.211.165.
Operating in obsolete linemode
Local character echo
Escape character is '^]'.

那么需要怎么做才能修复此问题呢？

In the article, only show as follow (because easy to show how to work):

Protocol: UDP; Port: 5234

Encoding: KV-GPB

For more detailed information, you can reference my colleague’s GitHub, which includes more examples, e.g GRPC.

AlexFengCisco / Telemetry_Receiver

GRPC Update Info:

If use GRPC not TCP/UDP, that will have standard function, you will not need to write “DECODE_FN_MAP…”, function will auto generate, direct to use. Simple list steps:

1. Get GRPC protobuf (e.g “mdt_grpc_dialout”) from cisco / bigmuddy-network-telemetry-proto
2. Install/use compile tools, suggest install python virtual env, you can reference 在MacOS中部署Python虚拟开发环境

(telemetry-protocol) [root@telemetry telemetry-protocol]# python -V
Python 3.6.8
(telemetry-protocol) [root@telemetry telemetry-protocol]# easy_install pip
(telemetry-protocol) [root@telemetry telemetry-protocol]# pip install grpcio
(telemetry-protocol) [root@telemetry telemetry-protocol]# pip install protobuf
(telemetry-protocol) [root@telemetry telemetry-protocol]# pip install grpcio_tools
(telemetry-protocol) [root@telemetry telemetry-protocol]# python -m grpc_tools.protoc -I. --python_out=. --grpc_python_out=. cisco_grpc_dialout.proto
(telemetry-protocol) [root@telemetry telemetry-protocol]# ls -l|grep cisco
-rw-r--r--.  1 root    root       2695 Aug 10 16:16 cisco_grpc_dialout_pb2_grpc.py   #generated
-rw-r--r--.  1 root    root       3805 Aug 10 16:16 cisco_grpc_dialout_pb2.py   #generated
-rw-r--r--.  1 root    root        485 Aug 10 16:15 cisco_grpc_dialout.proto   #proto file  

Follow all file if you need grpc protocol:

[root@telemetry grpc-dailout]# ls -l
total 36
-rw-r--r--. 1 root root  2695 Aug 10 16:16 cisco_grpc_dialout_pb2_grpc.py #Contains the server Stub class and the client Stub class, as well as the service RPC interface to be implemented.
-rw-r--r--. 1 root root  3805 Aug 10 16:16 cisco_grpc_dialout_pb2.py #message serialization classes
-rw-r--r--. 1 root root   484 Aug 10 15:36 mdt_grpc_dialout.proto 
-rw-r--r--. 1 root root  3722 Aug 10 16:11 service_grpc_dialout_no_tls.py #service python
-rw-r--r--. 1 root root 19220 Aug 10 15:58 telemetry_pb2.py  #decode gpb-kv messages, generate as below

grpc-dailout.zip

Install Protobuf of python version

完整阅读

The Linux come from by my compiled kernel that supports uSID, please check my last blog: Compile SRv6 uSID and VPP on ubuntu 20.04

Before doing SRv6 lab, please double confirm enable the function by following cmd:

sysctl -w net.ipv6.conf.all.forwarding=1
sysctl -w net.ipv4.conf.all.forwarding=1
sysctl -w net.ipv6.conf.all.seg6_enabled=1

Check by following cmd:

root@vm1:/home/cisco# sysctl -a |grep net.ipv6.conf.all.forwarding
net.ipv6.conf.all.forwarding = 1

Above cmd will disappear after reboot, you can permanently write to “/etc/sysctl.conf”.

Btw, how to config srv6 and usid, reference follows:

SRv6 uSID Linux Iproute2

SRv6 – Linux Kernel Implementation

Topology

完整阅读