MTU=1500, 为什么tcpdump抓到的udp的包长度为2048？

virdjx

问题： MTU=1500, 为什么tcpdump抓到的udp的包长度为2048？

ouput of tcpdump

10:58:07.172563 IP host001.mydomain.com.43915 > host002.mydomain.com.50933: UDP, length 2048
10:58:07.172590 IP host001.mydomain.com.43915 > host002.mydomain.com.50933: UDP, length 2048
10:58:07.172599 IP host001.mydomain.com.43915 > host002.mydomain.com.50933: UDP, length 2048
10:58:07.172635 IP host001.mydomain.com.43915 > host002.mydomain.com.50933: UDP, length 2048
10:58:07.172647 IP host001.mydomain.com.43915 > host002.mydomain.com.50933: UDP, length 2048
10:58:07.172659 IP host001.mydomain.com.43915 > host002.mydomain.com.50933: UDP, length 2048
10:58:07.172667 IP host001.mydomain.com.43915 > host002.mydomain.com.50933: UDP, length 2048
10:58:07.172685 IP host001.mydomain.com.43915 > host002.mydomain.com.50933: UDP, length 2048
10:58:07.172735 IP host001.mydomain.com.43915 > host002.mydomain.com.50933: UDP, length 2048
10:58:07.172747 IP host001.mydomain.com.43915 > host002.mydomain.com.50933: UDP, length 2048
10:58:07.172755 IP host001.mydomain.com.43915 > host002.mydomain.com.50933: UDP, length 2048
10:58:07.172762 IP host001.mydomain.com.43915 > host002.mydomain.com.50933: UDP, length 2048
10:58:07.172769 IP host001.mydomain.com.43915 > host002.mydomain.com.50933: UDP, length 2048
10:58:07.172834 IP host001.mydomain.com.43915 > host002.mydomain.com.50933: UDP, length 2048

q1208c

如果你在本机上 抓, 多大的都有可能, 因为这个包是在没有 分包之前的包. 而你收到的, 一定是分包之后的包.

ssffzz1

.pcap文件还有网卡的信息看下啊。