Time to live exceeded ???

billjie1

一個怪問題:
環境: fc6 centos 5.0   
我想把主機設成禁ping ...使用以下任何一條命令:
iptables -A INPUT -p icmp --icmp-type echo-request -j DROP
iptables -A OUTPUT p icmp --icmp-type echo-reply -j DROP


然后,我測試結果
在WIN下的是:
Pinging x.x.x.164 with 32 bytes of data:



Reply from x.x.x.168: TTL expired in transit.

Reply from x.x.x.168: TTL expired in transit.

Reply from x.x.x.168: TTL expired in transit.

Reply from x.x.x.168: TTL expired in transit.



Ping statistics for x.x.x.164:

    Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),

Approximate round trip times in milli-seconds:

    Minimum = 0ms, Maximum = 0ms, Average = 0ms



在linux 下的測試結果:

ping  x.x.x.164
PING x.x.x.164 (x.x.x.164) 56(84) bytes of data
From x.x.x.168 icmp_seq=1 Time to live exceeded
From x.x.x.168 icmp_seq=2 Time to live exceeded
From x.x.x.168 icmp_seq=3 Time to live exceeded
From x.x.x.168 icmp_seq=4 Time to live exceeded

--- x.x.x.164 ping statistics ---
4 packets transmitted, 0 received, +4 errors, 100% packet loss, time 3002ms

百思不得其解...??????(兩臺主機是在同個網段.用的redhat 4.0 做的router)..

ssffzz1

是不是有路由环路。
抓包分析一下。
另外如果把那2行去掉，什么结果。

billjie1

謝謝樓上的..去掉上面兩句,一切又正常了...很奇怪的..

ssffzz1

还是有地方配置不正确。
要解决的话，先帖完整的拓扑结构。特别注意有无ARP代理的地方。

wheel

TTL超时？

chenyx

检查有没有路由回环存在