How to connect guest from host in shared network mode?

[NanXiao]

Describe the issue
I am a newbie of Virtualisation, so very sorry for this naive question. I installed an OpenBSD VM, and the network mode is "shared network". The following is the ifconfig output from OpenBSD guest:

And from my host, I can find a new bridge100 NIC:

bridge100: flags=8a63<UP,BROADCAST,SMART,RUNNING,ALLMULTI,SIMPLEX,MULTICAST> mtu 1500
	options=3<RXCSUM,TXCSUM>
	ether 9e:3e:53:c6:52:64
	inet 192.168.64.1 netmask 0xffffff00 broadcast 192.168.64.255
	inet6 fe80::9c3e:53ff:fec6:5264%bridge100 prefixlen 64 scopeid 0x15
	inet6 fd47:e6a5:52a4:c3ca:1463:8bd1:b203:5aba prefixlen 64 autoconf secured
	Configuration:
		id 0:0:0:0:0:0 priority 0 hellotime 0 fwddelay 0
		maxage 0 holdcnt 0 proto stp maxaddr 100 timeout 1200
		root id 0:0:0:0:0:0 priority 0 ifcost 0 port 0
		ipfilter disabled flags 0x0
	member: vmenet0 flags=3<LEARNING,DISCOVER>
	        ifmaxaddr 0 port 20 priority 0 path cost 0
	nd6 options=201<PERFORMNUD,DAD>
	media: autoselect
	status: active

I tried to ping OpenBSD guest from host, but it failed:

$ ping 192.168.64.4
PING 192.168.64.4 (192.168.64.4): 56 data bytes
ping: sendto: No route to host
Request timeout for icmp_seq 0
ping: sendto: No route to host
Request timeout for icmp_seq 1

But ping bridge100 works:

$ ping 192.168.64.1
PING 192.168.64.1 (192.168.64.1): 56 data bytes
64 bytes from 192.168.64.1: icmp_seq=0 ttl=64 time=5.474 ms
64 bytes from 192.168.64.1: icmp_seq=1 ttl=64 time=0.400 ms 

So how should I connect to guest VM in shared network mode? Thanks very much in advance!

P.S., I read https://docs.getutm.app/settings-qemu/devices/network/network/#network-mode, but it seems there is no answer.
Configuration

• UTM Version: 4.6.5 (108)
• macOS Version: Darwin nanxiaos-MacBook-Pro.local 24.6.0 Darwin Kernel Version 24.6.0: Mon Jul 14 11:30:51 PDT 2025; root:xnu-11417.140.69~1/RELEASE_ARM64_T8112 arm64
• Mac Chip (Intel, M1, ...): M2