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  • 修改Linux服务器的ttl值

    [root@test_android_client_download ~]# cat /etc/sysctl.conf |grep net.ipv4.ip_default_ttl
    net.ipv4.ip_default_ttl = 28
    [root@test_android_client_download ~]# sysctl -p

    #动态修改,直接生效,这个文件保存在内存中的

    [root@test_android_client_download ipv4]# ll ip_default_ttl
    -rw-r--r-- 1 root root 0 Feb  9 11:15 ip_default_ttl
    [root@test_android_client_download ipv4]# pwd
    /proc/sys/net/ipv4
    [root@test_android_client_download ipv4]#

    [root@test_android_client_download ipv4]# echo 64 >/proc/sys/net/ipv4/ip_default_ttl

    [root@test_android_client_download ipv4]# ping 127.0.0.1
    PING 127.0.0.1 (127.0.0.1) 56(84) bytes of data.
    64 bytes from 127.0.0.1: icmp_seq=1 ttl=64 time=0.050 ms
    64 bytes from 127.0.0.1: icmp_seq=2 ttl=64 time=0.051 ms

    [root@test_android_client_download ~]# ping 127.0.0.1 -c 1

    PING 127.0.0.1 (127.0.0.1) 56(84) bytes of data. 64 bytes from 127.0.0.1: icmp_seq=1 ttl=28 time=0.044 ms

    --- 127.0.0.1 ping statistics --- 1 packets transmitted, 1 received, 0% packet loss, time 0ms rtt min/avg/max/mdev = 0.044/0.044/0.044/0.000 ms

    #抓包  -i 指定网卡 -t 指定协议 -n不解析IP为域名 v 显示详细信息

    [root@test_android_client_download ~]# tcpdump -i eth1 -n -v -t icmp
    tcpdump: listening on eth1, link-type EN10MB (Ethernet), capture size 65535 bytes
    IP (tos 0x0, ttl 28, id 0, offset 0, flags [DF], proto ICMP (1), length 84)
        112.124.111.141 > 180.149.132.47: ICMP echo request, id 62590, seq 1, length 64
    IP (tos 0x14, ttl 53, id 0, offset 0, flags [DF], proto ICMP (1), length 84)
        180.149.132.47 > 112.124.111.141: ICMP echo reply, id 62590, seq 1, length 64
    IP (tos 0x0, ttl 28, id 0, offset 0, flags [DF], proto ICMP (1), length 84)
        112.124.111.141 > 180.149.132.47: ICMP echo request, id 62590, seq 2, length 64
    IP (tos 0x14, ttl 53, id 0, offset 0, flags [DF], proto ICMP (1), length 84)
        180.149.132.47 > 112.124.111.141: ICMP echo reply, id 62590, seq 2, length 64

    如果把net.ipv4.ip_default_ttl = 1 服务器会上不去网,不能远程连接服务器,可以用内网连接,修改参数,恢复上网

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  • 原文地址:https://www.cnblogs.com/liuyoushui/p/6381192.html
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