我正在尝试为KVM来宾和主机系统之间的存储通信实现9000字节MTU.主机有一个桥接器(br1),其MTU为9000字节：

host# ip link show br1

8: br1: mtu 9000 qdisc noqueue state UP

link/ether fe:54:00:50:f3:55 brd ff:ff:ff:ff:ff:ff

inet 172.16.64.1/24 brd 172.16.64.255 scope global br1

inet6 fe80::21b:21ff:fe0e:ee39/64 scope link

valid_lft forever preferred_lft forever

客人有一个连接到此桥接器的接口,该接口还具有9000字节MTU：

guest# ip addr show eth2

4: eth2: mtu 9000 qdisc pfifo_fast state UP qlen 1000

link/ether 52:54:00:50:f3:55 brd ff:ff:ff:ff:ff:ff

inet 172.16.64.10/24 brd 172.16.64.255 scope global eth2

inet6 fe80::5054:ff:fe50:f355/64 scope link

valid_lft forever preferred_lft forever

我可以从主机ping到访客：

host# ping -c4 172.16.64.10

PING 172.16.64.10 (172.16.64.10) 56(84) bytes of data.

64 bytes from 172.16.64.10: icmp_seq=1 ttl=64 time=1.15 ms

64 bytes from 172.16.64.10: icmp_seq=2 ttl=64 time=0.558 ms

64 bytes from 172.16.64.10: icmp_seq=3 ttl=64 time=0.566 ms

64 bytes from 172.16.64.10: icmp_seq=4 ttl=64 time=0.631 ms

--- 172.16.64.10 ping statistics ---

4 packets transmitted,4 received,0% packet loss,time 3000ms

rtt min/avg/max/mdev = 0.558/0.727/1.153/0.247 ms

但是,如果我将ping数据包大小增加到超过1490字节,我就不再具有连接性：

host# ping -c4 -s 1491 172.16.64.10

PING 172.16.64.10 (172.16.64.10) 1491(1519) bytes of data.

--- 172.16.64.10 ping statistics ---

4 packets transmitted,0 received,100% packet loss,time 3000ms

数据包跟踪显示这些数据包永远不会到达来宾.我读过的所有内容都表明Linux桥接接口和virtio网络驱动器都支持巨型帧,但这对我来说肯定是一个MTU问题.

我错过了一些非常明显的东西吗

更新

显示访客接口的主机端：

host# brctl show

bridge name bridge id STP enabled interfaces

br1 8000.fe540050f355 no vnet2

host# ip addr show vnet2

11: vnet2: mtu 9000 qdisc pfifo_fast master br1 state UNKNOWN qlen 500

link/ether fe:54:00:50:f3:55 brd ff:ff:ff:ff:ff:ff

inet6 fe80::fc54:ff:fe50:f355/64 scope link

valid_lft forever preferred_lft forever